The Rodding Roundtable
Motorhead Message Central => Rodder's Roundtable => Topic started by: hotrodbob on February 02, 2005, 12:23:54 PM
Ok, I got tired of the light show under my dash and now there is a fresh ENOS wiring harness in the car. Everything works, but now the amp gauge will not show discharge only charge. I have tried with key on and key off, but even pulling out the head light switch will not cause a discharge to show on the gauge. Anyone got any Ideas on this? I'm using the stock gauges, ign switch.
The guy that installed it said he spoke to the ENOS guys and they said nothing is wrong. I kinda disagree.
Just tried to find a web address or phone number for ENOS but couldn't.
I'm not much help do to memory failure but I had the same problem years ago. I didn't have the ammeter hooked into the right place. I can't remember what I did to fix it. Sorry.
True system amp gauges should show SYSTEM discharge and charging but some wiring systems only show a discharge when the engine is running and there is no charge present out of the alternator. This depends on how the battery bus and alternator bus is designed and routed.
The old systems used to show discharge by simply pulling the headlights on with the ignition switch on...but engine not running and in some cases even without the ignition on.
For the gauge to work correctly the entire load HAS TO COME THRU the amp gauge shut which usually means the charging line and/or battery bus is involved. Without seeing how the system is wired or a schematic I can't tell.
But, a true test is to start the car without an alternator belt on and then for sure regardless of the type or how it's wired...it should show discharge. You can do this even if the water pump depends on the alternator being belted up to run the water pump. No problem for a 30 second check.
Great info. I had the stuff done for me so it's back to them with the info.
Got some other things to check as well.
Thanks
Quote: For the gauge to work correctly the entire load HAS TO COME THRU the amp gauge shut which usually means the charging line and/or battery bus is involved
Exactly why no-one should consider using an ammeter. I'd replace it with a voltmeter if I was you. Ammeters cause lots of problems.
I've never had a problem with an ammeter.
The use of voltmeters by the aftermarket wiring companies is a sales pitch.
The main load wire - usually 10 gage - has to come into the car's interior somewhere along the line so the so-called safety aspect of a voltmeter is a moot point.
Find the car's main source of supply.
It should be the 10 gage wire emanating from the hot side of the starter solenoid on GM or Ford products and ChryCo's are similar to Ford in most cases.
Splice the ammeter into this 10 gage wire where convenient and it will show charge and discharge.
If the interior run of 10 gage is not long enough to do what you want, remove it from the starter solenoid and pull it into the interior.
Hook that to one side of the alternator.
Run another 10 gage wire from ammeter to starter solenoid and connect the interior side of that to the other ammeter post.
Test the ammeter for proper connections by turning on the headlights with the engine off.
You should see about 10 amps on the discharge side.
If the ammeter needle deflects to the charge side with the headlights on (engine still off) reverse the ammeter's 10 gage wire connections.
You'll probably find that several circuits in the car tap directly off the load side of the ammeter and these circuits will be stacked on the ammeter post or tap off the wiring panel and only one 10 gage wire goes to the wiring panel from the load side of the ammeter.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Detroit quit using ammeters because voltmeters are a lighter duty - read cheaper - gauge than an ammeter as well as they can run a lighter gage wire to the voltmeter.
Saving a few cents per car with the lighter gage wire is not to be sneezed at when you're dealing with the quantities of cars coming off the line.
It can add up to some big bucks.
Back in the mid-60-'s I think it was, Ford used to have an employee suggestion box and they paid employees for ideas that were incorporated into the manufacture of the cars.
A suggestion that saved a nickel per car would net the employee a $2000. check.
C9....with all due respect,... me thinks you are a smiggin cynical here...I will argue all day long that ammeters are far more problematic than voltmeters and was IN FACT done for safety and moreover to eliminate voltage drops....not cost savings or simple sales pitches at all. Anytime you introduce current to any device, the overall failure/reliability rates go exponentially.
I personally have repaired more cars and trucks with electrical problems because of bringing large currents thru the dash to the block to the gauge and so forth including ammeter issues. These are usually junction issues creating large voltage drops or overloading of fuse blocks OR DEFUNCT AMMETER GAUGES.
In fact, the factories OEMs have established a "gold industry standard" (if you look at your modern rides) that they relay everything that requires over 10amps and keep the circuits as short as possible AND out of the interior. This is NOT a cost saving issue either and in fact is over double the cost....so it's about reliability, safety and eliminating voltage drops in wires and connections.
The safety factor is getting rid of a potential short in the interior with such a high load carrying wire if involved in an accident. Because it is not protected to a lower level such as A 10amp, 40amp or 60amp fused line etal, the heavy current lead could easily spark in an accident an ignite possible fuel situtions/scenerios in the interior. So, safety is NOT moot at all. (One of the more obscure facts from the old firey Pinto debacle in the mid 70s...if you remember being hit from the rear and exploding in a ball of flame,...it was found out that Pintos with ammeter gauges also ignited the interior that filled with pressurised fuel and did not happen in the case of interiors without when the car was jammed into a car in front of it.) This very subject (high current buss management) was highlighted at the University of Michigan's 2003 Automotive Conference on Automotive Engineering as well and every other slide/presentation was eliminating high current loads from the interior. Also a reason the high current relays and fuseblocks are now residing in the engine compartment instead of in the interior. My next car will in fact have the complete relay panel and fuseblock mounted outside the interior. I know in some rod applications its hard...but as an alternative the trunk can be used.
Also, another reason the OEMs went this way is that a voltmeter is a better tool for analysis of the overall system. The voltmeter can tell you if you are charging or discharging and moreover the health of the system voltage. It is also more accurate. This problem is exacerbated by age as well with junctions corroding etc. ...so that is why we are replacing alot of these systems today in older cars! Today's cars could easily go 100s of years of electrical service both with the design upgrades and materials.
"Splice the ammeter into this 10 gage wire where convenient and it will show charge and discharge" will not always work. Depends on how the charging system is hooked and and where. I respectfully submit that one gets a qualified person to determine this on an application if one cannot determine this themselve. And, I wouldn't splice the main circuit feeder bus for anything. Again, you are introducing voltage dropping junctions that could heat up under high loads. Not a good thing in my opinion.
Now...am I saying that ammeters are a bad thing when correctly installed and maintained......nope. I am just saying that voltmeters are a better mousetrap for lots of reasons.
Another side note and then I will get off my soap box. Now adays...10ga wire is NOT enough to feed most systems. This is especially true at the alternator leads to the battery or system. Many of us want high watt headlights, air, big stereos, electric seats, winders and huge cooling fans...well you get the idea. A simple unfettered 7 foot run of 10 gauge at 60amps produces a whopping half volt drop....then add connections and you can easily be talking almost volt! At 60amps that's 30 to 60 watts that are getting eaten up....all heating your wire. That's like a high beem headlight heat. I recommend at least an 8ga or adding an additional parallel 10 gauge to accommodate these current hogs. Just food for thought.
Good points - and no offense taken.
Splicing the ammeter into the main load wire was a poor choice of words.
What I meant here was to cut the wire, install terminals and install the ammeter in series.
More than likely voltmeters today are done for the safety aspect, but from what I've read the early VM's were done as a cost cutting measure.
I'd bet too that the ammeters and associated wires you've had problems with were brought into the interior without grommets and other devices to protect the wire.
I see some amazing things done with wiring in hot rods and I'm sure you've seen the same.
That's quite a voltage drop in only 7' of ten gage.
My experience has been what looks to be zero voltage drop with a 4' run of ten gage.
That's comparing voltage at the battery's main positive cable where it connects to the starter solenoid and at the end of the 4' run of ten gage where it connects to a relay utilizing the same ground point connection in both cases.
A good quality digital voltmeter was used and an analog voltmeter shows the same.
Not laboratory instruments, but accurate enough for field work.
Far as the choice of wire gage goes, ten gage seems to be sufficient for most of the hot rods I get involved with.
Simple cars with just the basics, ignition, lights, heater (sometimes) and radio (occasionally)
Which means ten to twenty amps running in the ten gage (lights and heater).
Ignition is not quoted here because it has it's own source at the solenoid and does not utilize the main run of ten gage.
I agree that the well equipped street rod with all the modern paraphernalia requires more than one ten gage wire or a larger wire as the main feed.
Interesting thoughts about setting up the wiring panel etc. under the hood or in the trunk instead of under the dash.
I'd guess that most hot rodders wouldn't want the panel under the hood on the simpler cars - thin fenders etc. - but it could be nicely done on the fat fendered cars.
In view of all the gas tanks in the trunk I'm not sure the wiring back there is the best set up either.
Last choice in panel location is under the seat which is convenient, but probably no safer than an under-dash setup.
Perhaps we need to think about getting our fuel tanks under the car within the perimeter of the frame and out of the trunk and off the exposed rear of the Deuces.
Problem here is lack of capacity, but twin tanks would cover that fairly well.
I'm planning for a pair of tanks within the frame perimeter in front of the rear axle.
Capacities would run from about 5 gallons each for a simple box and if there's a small extension run forward they would end up about 7 gallons each.
Interesting discussion and educational about the factory wiring et al and I'm sure safety - specially nowadays with our overly litigious society - is the big reason why Detroit does what it does.
Saving money enters into it as well.
Granted, relays cost more than wire, but maybe that's a wash considering all the wire we have in modern cars.
Not to mention the 32 volt systems that are coming on line with their commensurate very small wire gages.
I believe much of the circuitry will be 20-22 gage wire.
That'll save Detroit some money, but it seems that mechanical weakness of the wiring could create problems not seen with the structurally stronger wiring in use today.
Easily cured by grommets, good harnesses and proper support no doubt, but I have yet to see a modern car that didn't need a few tie wraps added to forestall potential problems.
Even so, I have yet to see a failed ammeter - or a failed voltmeter for that matter.
Making an ammeter my first choice for the new car - with thoughts about adding a voltmeter as well.
Carefully installed the ammeter will not cause problems, but requires considerable effort to do it properly. The ideal solution is to use a remote shunt ammeter.
A quick description for those not familiar with this type of instrument. A typical automobile ammeter has a thick copper strip running between the terminals. This "shunt" carries the large currents passing in and out of the battery, and the meter movement is in fact a sensitive volt meter which measures the small voltage drop across the shunt.
A remote shunt ammeter has the shunt at the engine and a pair of light gauge wires carry the small current (about .05A) required to operate the meter movement. These are used routinely in marine applications where there is a long distance from the batteries to the cockpit instrument panel making a direct reading type impractical and have also been used on some cars and trucks.
"Off the shelf" remote shunt meters are unlikely to match your other instruments, however all is not lost if you do not mind a little fiddly work. Some conventional ammeters have the shunt mounted on the terminal studs outside of the case allowing it to be easily be removed and relocated in the engine bay. On most older automobile gauges bending up a couple of tabs on the ring that retains the glass allows the unit to be dismantled and the shunt removed. Later instruments with shunt inside the case and crimped glass rings are too difficult to modify.
Some readers will believe all this simply reinforces the reason for using a voltmeter which only requires one terminal spliced to the ignition circuit and the other to ground. To provide an accurate measure of battery voltage the voltmeter should take the reading at the battery, not at the end of a long cable subject to load dependent voltage drop.
Running a pair of light gauge wires from the meter to the battery lead terminal at the starter and the main ground cable will solve the voltage drop errors, but also flatten the battery if the vehicle is left standing for long periods. This is overcome by fitting a relay in the +ve lead close to the meter with the relay coil feed from the ignition. The meter will then monitor the real battery voltage but be disconnected when the engine is not running.
Quote from: "HOTRODSRJ"True system amp gauges should show SYSTEM discharge and charging but some wiring systems only show a discharge when the engine is running and there is no charge present out of the alternator. This depends on how the battery bus and alternator bus is designed and routed.
The old systems used to show discharge by simply pulling the headlights on with the ignition switch on...but engine not running and in some cases even without the ignition on.
For the gauge to work correctly the entire load HAS TO COME THRU the amp gauge shut which usually means the charging line and/or battery bus is involved. Without seeing how the system is wired or a schematic I can't tell.
But, a true test is to start the car without an alternator belt on and then for sure regardless of the type or how it's wired...it should show discharge. You can do this even if the water pump depends on the alternator being belted up to run the water pump. No problem for a 30 second check.
A correctly wired automotive ammeter will have ALL of the loads attached to the charging device side of the ammeter and ONLY tyhe battery (at the starter solenoid end of the cable) connected to the other side.
With the engine off, current flows between the battery and the loads THROUGH the ammeter.
With the engine running, the charging device supplies the necessary current and only a trickle charge fllows into the battery (after the initial top-off charge to replenisg voltage drop due to engaging the starter motor) so the ammeter needle should rest just slightly into the charging zone.
Hey Skip! Haven't seen ya around for awhile. I knew this was the perfect post for you!
I do have a quick question for you. What do most gas gauges resistances/impedances look like? Any idea? I don't know of a standard do you?
Quote from: "HOTRODSRJ"Hey Skip! Haven't seen ya around for awhile. I knew this was the perfect post for you!
I do have a quick question for you. What do most gas gauges resistances/impedances look like? Any idea? I don't know of a standard do you?
Empty Full
VDO 10 Ohms 180 (could be backwards)
Ford 73 10
SW/Sun 240 33
GM 90 0
GM 0 30
Autometer 30 250 (could be backwards)
Moon 31 199 (could be backwards)
I say these readings could be backwards because grounding the sender wire at the gauge makes they needle read full, which is opposite from the specs I was given. i.e. grounding the wire should force the needle to empty.
Quote from: "HOTRODSRJ"Hey Skip! Haven't seen ya around for awhile. I knew this was the perfect post for you!
I do have a quick question for you. What do most gas gauges resistances/impedances look like? Any idea? I don't know of a standard do you?
Oh, yea. Been prettyy busy wiring cars after work so I don't get on line much. Inbetween wiring jobs right now (that'll change tomorrow night) so I have a bit of free time.
I'm at work before 7:30 (after an hour's drive) then I wire cars Mon-Thur every week in the evenings. Friday light's the tiome to relax and that DOESN'T mean on the 'puter. Sat & Sun is catch up on my own stuff time.
Been too cold to work on the '34 so I've been catching up on all tyhe 'lectric train jobs that have been piling up (converting a guy's fleet of diesels to DCC)
Hello everybody.
Choco speaking.
Car manufacturers switched to Voltmeters (even though, in the early 60s, they were labelled Amps but were really voltmeters) because of the change from generators to alternators. Generators were current sensing, alternators are voltage sensing. It's still OK (sorta) to put an ammeter in series with the alternator charge wire, but today's wiring systems are designed around using a voltmeter.
I really like it here. I should visit more often. I love you all.
BCNU
Quote from: "choco"
Car manufacturers switched to Voltmeters (even though, in the early 60s, they were labelled Amps but were really voltmeters) because of the change from generators to alternators. Generators were current sensing, alternators are voltage sensing. It's still OK (sorta) to put an ammeter in series with the alternator charge wire, but today's wiring systems are designed around using a voltmeter.
BCNU
Isn't it nice every once in a while to be told the real reasons along with the pitfalls, quick fixes and catastrophies? GPster
I suspect there are a number of reasons ammeters have fallen out of favour in production passenger vehicles, and surprisingly none of them has been raised in the posts above.
1. In dem olden days before alternators, typical auto generators had an output of 19amp and the real big heavy-duty models had an output of 26amps. Even though cars of those days were not loaded up with accessories, driving on a wet cold night with the load of ignition, lights, wipers and demister fan meant the generator would be struggling to cover the demand and any small deterioration in performance inevitably resulted in the battery being drained. This meant the charge light alone could not be relied upon to indicate a satisfactory charge condition.
When alternators came along their output was almost double that of the generators they replaced. If the charge light did not illuminate then the driver could be confident the alternator would be producing sufficient current to cover demand so there was little need for an ammeter.
2. If a generator equipped engine is switched off or running at low revolutions the generator output voltage is lower than the battery voltage, and if permanently connected the battery would discharge into the generator. To prevent this a low-voltage cut out relay in the charge lead isolated the generator under these conditions.
Also, the armature resistance of a generator is very low (less than 1ohm), accordingly the source resistance of a generator is small. Similarly a battery has a very low internal resistance and if the battery is almost flat the generator will attempt to pump in current at a rate beyond the safe capacity of the armature windings. To prevent permanent damage from excessive current, generators had an external current limiter.
The low-voltage cut out and the current sensing coil were within the voltage regulator which was usually mounted on the firewall. This meant heavy gauge wiring was already at the firewall and extending it a few inches to run an ammeter was not an expensive exercise.
Though the primary function of the rectifier pack in an alternator is to convert the AC voltage off the coils to DC, it also prevents current flowing backwards into the alternator eliminating the requirement for a cut-out relay. The stationary coils in an alternator have a large inductance and as there is AC flowing through these an alternator is inherently current limiting making over-current control unnecessary. These two features allow an alternator to be connected directly to the battery. Typically the charge cable from alternator to battery post is about two feet, but has to be extended by at least ten feet if a dash ammeter is fitted adding to the cost and introducing undesirable voltage drop in the charge circuit.
3. After the introduction of alternators as standard equipment some vehicles retained ammeters however they frequently caused driver anxiety. The regulators used at that time were the mechanical type with three stages of charge; low, medium and flat out. If an engine idled for some time the regulator would go to the highest setting, then when the engine revved up, the charge rate rocketed to maximum pegging the ammeter until the regulator dropped down a notch. The solution to this was fitting a voltmeter instead of an ammeter. As long as the needle remained in the green zone the driver felt content, and as a bonus these cost about a quarter of the price of an ammeter, and avoided the long runs of heavy gauge cables.
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The reality is that when used in automobiles modern alternators with solid state regulators do not require meters at all, a simple charge light is quite adequate.
The long leads associated with internal shunt ammeters cause voltage drop in charge circuits but if routed correctly are not dangerous as some suggest.
To be useful a voltmeter must read to fractions of a volt making the modern cheap thermal movement voltmeter connected to a heavily loaded ignition circuit serve little more purpose than to fill a hole in the dash.
The situation in marine and aero applications where the consequences of failure may be life threatening is different, but even here the argument of whether to use an ammeter which indicates trouble looming ahead, or voltmeter that confirms there is already trouble will go on forever. Installing a remote sensing voltmeter and remote shunt ammeter settles the argument by providing all the attributes of both without any of the disadvantages of either.
Thank you, Peter, for taking the time to do all that typing! :shock:
As usual, your explanation was thorough, clear, and VERY informative. ....I always learn something from your posts!
Thank you!
~~~~Bruce
I built my dash using gauges from a '64 Malibu. It came with a shunt type ammeter as described above. On the Malibu setup the shunt looked like a ballast resistor. Long story short: it broke and ALL the charging current went thru the tiny wires to the ammeter. Smoke filled the interior. I changed to a cheap ammeter that put the charging current thru the ammeter. I never really liked it and it was difficult for my old eyes to see a discharge. I finally changed to a voltmeter. It is much easier to see a problem.
Quotestory short: it broke and ALL the charging current went thru the tiny wires to the ammeter. Smoke filled the interior
And what does that indicate you forgot to do during the instalation.
Install a voltmeter!
This used to be a common problem on some models. If the shunt which is the low impedance path opens, then all the current is trying to go thru the meter directly and hence fries the small wires and not to mention the gauge.
Peter-
I assume you mean either a fusible link or Maxi-Fuse. My only defense is that the install was in 1976 and I didn't know as much about wiring then. The car now has a fusible link but I'll probably change to a Maxi-Fuse when I convert to a higher amp alternator this spring.
what exactly is a maxi fuse and how do they differ from regular fuses and resetable fuses. I believe I have herd the term used on tv when refering to large wattage stereo systems. Ed ke6bnl
Quote from: "model a vette"I built my dash using gauges from a '64 Malibu. It came with a shunt type ammeter as described above. On the Malibu setup the shunt looked like a ballast resistor. Long story short: it broke and ALL the charging current went thru the tiny wires to the ammeter. Smoke filled the interior. I changed to a cheap ammeter that put the charging current thru the ammeter. I never really liked it and it was difficult for my old eyes to see a discharge. I finally changed to a voltmeter. It is much easier to see a problem.
How does a volt meter tell you there's a problem?
All a volt meter tells you is that there's a specific voltage at the back of the meter. It DOESN'T tell you whether this voltage is sufficient or if the battery is slowly going south because it isn't being charged.
Some of the new, maintenance-free batteries need a charge voltage WELL ABOVE what an old lead-acid battery requires. How do you know what voltage is "enough" and what's not enough. What's too much?
With an ammeter, anything over an amp or two (once the starting voltage has been replenished) is too much. If the charging system isn't up to the task, the needle moves towards "discharge". If it's straight up, it's good. If it's pushing to either side, you have a problem. Pretty simple when you compare it to a volt meter.
Whenever the words voltmeter or ammeter are uttered there is that bizarre reaction similar to discussions involving front steer vs rear steer, carb vs injection, stick vs auto, drums vs disks.
For some reason utterly beyond my comprehension there is a belief that an ammeter is the fire breathing dragon and a voltmeter the knight in shining armour.
Most of the criticism directed towards ammeters has been based on fault conditions of poor installations, when it should have been directed at the installation rather than the device. No one has raised the issue of what happens when a fault occurs in a voltmeter attached directly to the ignition switch and the main feed does not have a fusible link.
The reality is that they are simply electrical devices and if correctly installed either is safe: if poorly installed both are dangerous.
If there is something intrinsically unsafe about conductors carrying large currents then every automobile with trunk mounted battery would have burned to the ground, there would be smoke pouring from vehicles with a seven pin trailer socket, and dash mounted cigarette lighter sockets would have been banned by insurers.
Modern alternators with electronic regulators control are extremely reliable, and in the vast majority of applications there is no need for a meter at all. In the unlikely event a battery goes flat from lack of charge generally the outcome is a mild inconvenience, however if an engine losses oil pressure the outcome is far more serious yet people are quite happy to place their trust in a low pressure light.
Quote from: "PeterR"Whenever the words voltmeter or ammeter are uttered there is that bizarre reaction similar to discussions involving front steer vs rear steer, carb vs injection, stick vs auto, drums vs disks.
For some reason utterly beyond my comprehension there is a belief that an ammeter is the fire breathing dragon and a voltmeter the knight in shining armour.
Most of the criticism directed towards ammeters has been based on fault conditions of poor installations, when it should have been directed at the installation rather than the device. No one has raised the issue of what happens when a fault occurs in a voltmeter attached directly to the ignition switch and the main feed does not have a fusible link.
The reality is that they are simply electrical devices and if correctly installed either is safe: if poorly installed both are dangerous.
If there is something intrinsically unsafe about conductors carrying large currents then every automobile with trunk mounted battery would have burned to the ground, there would be smoke pouring from vehicles with a seven pin trailer socket, and dash mounted cigarette lighter sockets would have been banned by insurers.
Modern alternators with electronic regulators control are extremely reliable, and in the vast majority of applications there is no need for a meter at all. In the unlikely event a battery goes flat from lack of charge generally the outcome is a mild inconvenience, however if an engine losses oil pressure the outcome is far more serious yet people are quite happy to place their trust in a low pressure light.
Yes I agree. Ammeter is a buzz word. I do put in a fusible link in the 10 ga. wire not for fear that the ammeter will fail but for fear that the highly reliable alternator might fail. (again) I had an alternator short out while driving. The 10 ga wire carried every amp left in the battery staight to ground inside the alternator. The old SW ammeter handled the load with no problem, unfortunately. Even without an ammeter the charging circuit would have melted all the wires in the loom. A cheap fusible link would have blown instantly saving the wires. I don't think anyone would think that a GM alternator is dangerous. I don't but, a fusible link is cheap insurance. IMHO
Skip-
As I stated I couldn't see the ammeter well enough to determine a slight discharge vs. a "zeroed" needle. The voltmeter tells me that the alt is charging, when I start, because it shows 14+ volts going to the battery and the rest of the system. If it shows 12 volts I know something is wrong. If the voltmeter drops to less than 12 volts I know I have too much load or the alt or battery took a dump.
How does a ammeter show a bad battery? It would still show a charge flow even if the battery was going bad.
In the end both the ammeter and voltmeter have their good and bad points.
if it drops below 15 volts with a current generation battery you have a problem.
the trouble is, you need to know what generation of battery is under the hood to be able to make any sense of an ammeter.
An idiot light tells you a LOT more about the charging system than a volt meter does if all you want to know is if it's charging or not.
Ammeter is best, idiot light is next and the volt meter is the least usefull for this particular task.
Quote from: "Skip"if it drops below 15 volts with a current generation battery you have a problem.
the trouble is, you need to know what generation of battery is under the hood to be able to make any sense of an ammeter.
An idiot light tells you a LOT more about the charging system than a volt meter does if all you want to know is if it's charging or not.
Ammeter is best, idiot light is next and the volt meter is the least usefull for this particular task.
I have to respectfully disagree if evaluating the overall application. If the voltmeter shows more than the full battery charge voltage(12.65V for lead-acid) then you know the alternator is holding the charge up...it's that simple. Don't make it toooo complicated. I don't have any idea why you think anything below 15 volts is an issue when in fact most alternators won't produce that under most conditions. What's up with that? Please explain further whereas I can't figure that statement out?
Idiot lights are inherently subject to higher failure rates due to the bulb aspect failure alone. LED indicators would be far more trusting to split hairs here for the idiot light.
While I will agree that properly installed amp meters are okay.... in alot of these cars with heavy loads (my 57 pulls in excess of 85+ amps in full tilt position) and I sure am not going to pull all that thru a wire to the interior for sure. Modern OEM wiring systems use a "tree" style desigin with alots of branches and relays to keep high loads off the main bus and relay everything over 10amps. This is done for reliabililty, voltage drops and safety. As I have pointed out earlier, safety experts have lobbied to get high current carrying devices out of the interior due to their designed and inherent ability to carry very high currents under "shorted" conditions making for a greater likelihood of fire or fuel ignition. I could offer a library of information here on that, but all of these articles are copyrighted to authors or schools or companies. Join the American Society of Automotive Engineers and subscribe to their series to learn more.
I also point out that ammeters will show so little deflection on the meters scale that most people are not aware that they are operating effectively, if at all.....or can't read them. This was an inherent problem of the "ergonomics" side of this subject and witnessed right here in this forum with an anecdotal post. I think that is a very good reason to go away from ammeters.
FWIW, I too have always been a proponent of fusible links. Some people use them...some not unfortunately. But, you can have a "limited" fault on highly "fused" lines that can provide as much of a problem as a short. So, very high current one wire sources and protected as such are vulnerable to these problems.
"The reality is that they are simply electrical devices and if correctly installed either is safe: if poorly installed both are dangerous." I agree completely.....but...these designs can be improved on as proof by the modern automotive electrical system.
"If there is something intrinsically unsafe about conductors carrying large currents then every automobile with trunk mounted battery would have burned to the ground, there would be smoke pouring from vehicles with a seven pin trailer socket, and dash mounted cigarette lighter sockets would have been banned by insurers."... well "every automobile" is a little strong...don't ya think?...... and moreover ..... we are talking perhaps 100+ amps potential ....not a measily 10amps or 20 for that matter?? Completely different realm of current and these examples are not considered heavy loads by any means.
FWIW, I have seen three trunk mounted battery vehicles in fact in minor rear-end collosions and burn to the ground because the positive lead shorted to ground with no protection. This is why I put a master fuse (150amps) within 18" of my positive lead at the battery to the starter. So, it does happen to turn your example around.
Just my two sense.
FWIW, I have seen three trunk mounted battery vehicles in fact in minor rear-end collosions and burn to the ground because the positive lead shorted to ground with no protection. This is why I put a master fuse (150amps) within 18" of my positive lead at the battery to the starter. So, it does happen to turn your example around.
Just my two sense.[/quote]
Since you folks seem to be well versed in electrical systems, what and where do you recommend master fuses or fusible links and what capacity for general street rods.
I have, over the years, done a fare amount of rod wiring and usually use a master disconnect switch in the batter positive cable. The last car I did we used a master fuse in the battery, alternator, starter loop. I would like more of this protection incorporated into wiring systems and as I do most jobs from scratch, I would like to know capacity and location that would be best to protect most rods.
Thanks, Ken
Quote from: "Ohio Blue Tip"FWIW, I have seen three trunk mounted battery vehicles in fact in minor rear-end collosions and burn to the ground because the positive lead shorted to ground with no protection. This is why I put a master fuse (150amps) within 18" of my positive lead at the battery to the starter. So, it does happen to turn your example around.
Just my two sense
Since you folks seem to be well versed in electrical systems, what and where do you recommend master fuses or fusible links and what capacity for general street rods.
I have, over the years, done a fare amount of rod wiring and usually use a master disconnect switch in the batter positive cable. The last car I did we used a master fuse in the battery, alternator, starter loop. I would like more of this protection incorporated into wiring systems and as I do most jobs from scratch, I would like to know capacity and location that would be best to protect most rods.
Thanks, Ken
GREAT QUESTION maybe it can be put in a new thread so as to allow it to be saved in the tech section.
thanks jim
GREAT QUESTION maybe it can be put in a new thread so as to allow it to be saved in the tech section.
thanks jim[/quote]
Good idea, I'll start a new post. Frank will hve to delete this one because it's to late for me to delete.
QuoteSince you folks seem to be well versed in electrical systems, what and where do you recommend master fuses or fusible links and what capacity for general street rods. I would like more of this protection incorporated into wiring systems and as I do most jobs from scratch, I would like to know capacity and location that would be best to protect most rods.
Thanks, Ken
I would like just to throw my general response in for this purpose.
First, automotive wiring has become more and more complicated as it grows toward the more modern auto designs with the likes of power everything, EFI and high capacity batteries, charging systems and wiring to go with and even EMI/RFI and sophisticated alarm issues coming to the surface. As we all know it used to be a simple 8 or 9 circuit issue and pretty straight forward.
I would like to address the subject of capacity first and I could easily write many pages on this, but others I am sure will chime in with their experiences and takes as well. This depends more or less on your system's design or application's demand. As I have pointed out, some applications such as roadsters and others with little or no auxillery power needs, have a very simple demand and relatively light loading compared to modern day vehicles. The way I figure demand is do a balance sheet of peak load then add another 50% for main fusing. Lightly loaded systems often require no more than a 100 amp fuse (keep in mind that I ONLY USE mini starters and do not use the old boat anchors/starters of yesteryear which take more current ...alot more current!). I jump from there to a 150amp main fuse on most applications up to 100amp peak/nominal DC current loads. I locate all my main fuses within 18" of the battery itself regardless of location. This protects all but 18" of the main feed wherever it goes.
My 57 Belair is just about as power burdened as you can get and I have never exceeded 100 amps peak (I actually have a DC shunt that can easily measure this accurately) nominally. This includes a 25 amp cooling fan, 1200watt stereo, six-way power seats, high wattage headlights, air, yadda yadda yadda. The 150amp main fuse is what protects the total system.
But, fusible links or the more modern maxifuses are necessary too to compliment the main protection system. Again, the capacity of the fusible links depends on the alternator and bus demand. I put my links nearest the feeding source. This protects the whole bus branch. So my fusible link from the alternator is at the alternator. My maxifuse(s) is located at the source of the feed for the fuseblock and/or relay bus.
I do have some wiring/electrical system suggestions to keep things more with modern OEM designs and specifications. These are MY suggestions.
1. Always located your main fuse within 18" of your battery....actually the closer the better.
2. On-off switches offer no practical protection for system dynamic situations. Plan accordingly.
3. Aux relay any circuits that are over 10 amps external to the interior, if possible (you will have brighter headlights, more output from fans and less voltage drops due to length of wire and connections).
4. Always use fusible links or maxifuses accordingly.
5. Use high quality automotive/appropriately rated wire/insulation for all circuits. This includes battery cables. (and this will open up a can of worms...I know alot of guys out there using rubber coated welding wire/cable and while these are great conductors and very flexible cables.... if not installed correctly with the ends completely sealed from the elements they will wick water up in the cable itself and eventually fail...quickly. Notwithstanding that fact, the coating/insulation is NOT rated for fuel fires and/or heat and can easily be compromised in a high heat or fire situation adding another problem in a simple fuel fire to becoming an electrical issue as well. There is just too much other engineered cables for this purpose and I highly recommend them albeit more $$$).
6. Use only quality crimping tools, skip the cheap ones. Usually gas tight connections are wanted for all applications. With quality crimps, soldering is not necessary at all!
7. When replacing an old battery, consider a newer technology such as a spiral-cell technology (Optima). These do not leak acid, no gassing, provide a longer shelf charge (meaning no tender necessary), and can be mounted in any attitude you can invent.
8. Dump your old fashion field-wound starters. These take tons of current, are hard on your battery, require large conductors/connectors, heat soak easily, weigh a ton and are now relatively huge compared to perm mag starters....what else do you need to know?
9. Use quality automotive relays that are rated at least 30 amps and most preferably 40amps and in some cooling fan situations....70amps! Pay attention to the nominal currents of these devices for reliable designs.
10. Use "bucking" diodes on cooling fans of more than 15amps. This will eliminate large inductive spikes on your system.
11. Relay sockets (not PC board ones!) are preferable to just relay wires with terminal connections.
12. Do not put any mechanical stress or torsion or at least minimize such on any electrical wire or connection.
14. Screw clamping/termination type fuse blocks are prone to heat cycling issues and failure. I highly recommend against them. The GM block designs/types are as good as it gets.
I am sure others will have more to offer on this subject.
Lead acid batteries aren't used in production vehicles anymore. Lead acid batteries are the kind you have to periodically add water to.
Newer batteries require higher charging voltages than lead acid batteries. That's why it's not uncommon to see a voltmeter in the 16 volt6 range on a newer vehicle.
Now, if you're still running a lead acid battery, 16 volts is cooking your battery. If you're running a low maintenance battery, 12.5 volts is too low and you want to be up around 13.6. For maintenance free batteries you want to be close to 15.
which battery is under the hood?
Quote from: "Skip"Lead acid batteries aren't used in production vehicles anymore. Lead acid batteries are the kind you have to periodically add water to.
Newer batteries require higher charging voltages than lead acid batteries. That's why it's not uncommon to see a voltmeter in the 16 volt6 range on a newer vehicle.
Now, if you're still running a lead acid battery, 16 volts is cooking your battery. If you're running a low maintenance battery, 12.5 volts is too low and you want to be up around 13.6. For maintenance free batteries you want to be close to 15.
which battery is under the hood?
Okay Skip....I see what you are talking about. Yep...I agree. Thanks for clarifying this.
For the most part if you are above the full charge voltage of a battery at 12.65 is good. 16 would be too much for most common batteries.
Wow, I sure started a interesting thread.
Lemme explain the situation I have. The new wire harness instructions had us hook up the ammeter so that it only shows charge. If I turn on the lights, fan or anything the meter will not show a discharge. By my way of thinking, this is dumb. ENOS did not agree. I use my guage (OEM 1948 Plym) to check brake light operation before I drive as well as other systems to ensure they are working. As ENOS has it, I can't check anything as the guage will not show any electrical action other then charging. Even at idle with everything turned on the system would not show discharge. That bothers me. My alternator is only a 30 amp GM unit.Based on the info you guys have provided we will rewire the guage and I will add a new ground for the rear mount battery.
The info on this thread has been great.
I knew while typing up my early post which attempted to hose down some of the hysteria surrounding ammeters it would open a can of worms but the silly boy that I am still pressed the "send" key. But I have learned my lesson and this is my last post on this or related topics.
Most of the discussion has revolved around catastrophic fault conditions, and while fault conditions should be taken into account, they should not cloud the normal operational situation. I illustrate this with an unfortunate accident.
A friend of mine was working under a truck with the front end supported on jack stands. A mechanic working on the engine dropped a spanner which fell on the starter solenoid, the engine cranked over, drove the truck off the stands and onto the person working below. Neither his widow nor the coroner suggested the world should ban starter motors and revert to crank handles to start engines.
A couple of contributors have related stories of trunk mounted batteries causing fires as though that determines everyone of them to be unsafe, but do not blink an eye at rear mounted fuel tanks and high pressure fuel lines running the full length of the vehicle.
There has been condemnation of remote shunt ammeters because they can cause problems --if not installed correctly.
Failure of idiot generator lights was mentioned. Over a period of almost 50 years working on motor vehicles I have never seen an OEM idiot light fail, but have witnessed plenty of aftermarkets give up the ghost. The lamp used in an OEM application is under-rated and those of you familiar with life ratings of tungsten filament lamps will confirm that even a modest de-rating increases life enormously.
The examples above are intended to illustrate that many of the problems described by others are the result of inappropriate materials and unsound practices not the particular equipment blamed.
Just to prove that I am a real masochist I will reiterate a couple of points Skip and I have endeavoured to convey.
To be meaningful a voltmeter must read the voltage at the battery terminals, this means running dedicated leads from the battery to the meter negating all the so called simplicity and "safety" of the device. The meter then has to be calibrated to the particular style of battery and read to a fraction of a volt.
A correctly installed ammeter indicates the net charge rate and if showing a bit on the +side, then that is good enough, regardless of battery type or placement.
Three further comments then I will pull my head in.
1. QuoteScrew clamping/termination type fuse blocks are prone to heat cycling issues and failure
Screw connections with the conductor held under the head of the restraining screw have a high failure rate due to stress relaxation of the copper, however if the conductor is constrained within a tunnel they are fine as indicated by their near universal use in high current (1000A plus) applications. Never, never, never ever tin the end of a conductor with solder if it is be terminated in a clamped connector. Over time the solder "flows", the clamping force is reduced, the joint resistance increases causing heating, the solder softens and the joint progressively deteriorates.
2.
QuoteAs ENOS has it, I can't check anything, as the gauge will not show any electrical action other then charging. Even at idle with everything turned on the system would not show discharge. That bothers me.
Sometimes ammeters are wired (incorrectly) to show the full alternator charge, not the net charge, presumably to give drivers a warm fuzzy feeling when they see all those amps running down the wire.
As Skip noted,
QuoteA correctly wired automotive ammeter will have ALL of the loads attached to the charging device side of the ammeter and ONLY the battery (at the starter solenoid end of the cable) connected to the other side.
3.
QuoteUse "bucking" diodes on cooling fans of more than 15amps. This will eliminate large inductive spikes on your system.
With the ever-increasing array of electronic equipment in motor vehicles this is becoming even more of an issue and it is good practice to clamp any inductive load, even relay coils.