Alternator/ammeter

[Crosley.In.AZ]

Very interesting line of discussion.

[Skip]

Thanks, everybody is right and working from the information you've given with the supplies I have this is what I think I'll try. The negative battery cable will go to the case of the alternator and a jumper will continue on to the engine block. The 10 ga. secondary wire off the negative side post battery terminal will go to a body ground. The large cable from the positive side post battery terminal will go to the 12 volt solenoid on top of the 6 volt starter. The 10 ga. secondary wire off the positive side post battery will go to the "-" side of a 100 amp ammeter which will be mounted under the hood near the battery. The ammeter will be there as a positive junction place and as an under hood indication of charging. I already have it and it will serve as to keep the high amperage from having to find it's way in and out of the firewall to reach the stock dash ammeter which is not up to the full task. The "+" side of the under hood ammeter will have the positive  wire coming from the alternator and the wire going through the firewall to the ignition switch  and the stock ammeter which might only tell me if something is still "turned on"
or "shorted". The only load that the stock ammeter will see is the ignition, starter solenoid, lights and the motor and speed control resister for the heater/defroster fan. I sure can be complex trying to make things simple and all of this while celebrating my 38th wedding anniversary and the company of our 4 year old granddaughter. I can only do one thing at a time. GPster

Putting a 100 amp ammeter out under the hood is, in my opinion, a total waste of time.

What "heat" are you worried about getting "inside" the car?

Regardless of where you put that 100 amp ammeter, the same degree of heat will be inside the cabin.

The "heat" you're worried about is heat generated by the operation of the vehicle, itself.  All of this rise in temperature in the wiring system occurs BEFORE THE AMMETER.  The current flowing through these wires, regardless of whether you have an ammeter or a volt meter, ranges from 5 to 50 amps, depending on what you have running at the time.

The current flowing through the ammeter is only 2 amps.  A fully charged battery signals the alternator to produce only an amp or two more than that which is required to operate the rest of the vehicle.

If the engine speed is inadequate, at idle, to maintain the required current load, the battery must come into play to assist the alternator in supplying the necessary current.  In this instance, the ammeter will swing over to the "discharge" side indicating an insufficient charging current.  A volt meter won't indicate a sudden discharge until the battery voltage has depleted to the extent that a perceptible movement in the needle is noticed.    An ammeter indicates a problem like this INSTANTLY.  

Bring the engine revs up a bit should case the charging system to recover.  This is an indication that you have 1, too large a pulley on the alternator, 2. too heavy a load for the alternator to handle at low engine seeds,  or – if this didn't happen previously – a faulty alternator (defective diode, worn brush, etc) or a device such as your electric fan that has worn bushings and is using sufficiently more current than when it was new.

The ONLY time you have more than 2 amps current flowing through the ammeter is when the alternator is replenishing the voltage loss in the battery due to the demands of the starter motor.  Once this initial drain is replaced, the voltage regulator lowers the charging current sufficiently to create a 2 amp trickle charge into the battery.

If you want to get an idea of how much current is flowing around under your dashboard, turn EVERYTHING on except the engine and look at how far the ammeter needle has moved towards discharge.  THIS is what's under the dash regardless of whether you have an ammeter of a volt meter.  If you don't have an ammeter in the circuit, put a temporary test ammeter into the circuit.  Simply remove the positive battery cable and connect an ammeter between the battery cable and the positive post of the battery and turn everything except the engine on.  For some folks, this is a really rude awakening.

FWIW, your in-the-car ammeter hookup won't tell you that the ignition, lights etc. are working UNLESS you connect it up backwards, in which case you'll see it pegged most of the time.

[PeterR]

amp meters are one of the largest causes of old auto fires
they are by design a point of resistance in the circut  
please think about having it converted to a voltmeter  these little beautys tell you far more than any amp meter
I think ron francis used to post a warning in his adds about amp meters
amp meter runs in series   (bad)
volt meter parallel.  volt meter tells battery volts when key on . then goes up slow to 13.8

I don't have the energy to go through all this again, so Skip it is in your capable hands to bring some sense to these myths.

[GPster]

Skip, thank you for the time with your explanations. I'm not going to try to tell you I'm right but only give you an idea of why I was thinking the way I did, which will probably change. The 100 amp ammeter under the hood was mostly a place with insulated terminals to separate the 10 ga. wires from the chassis ground neatly. My neatness concern is mostly concern over the jumble of wires. The alternator is on the same side as the battery and the ammeter and ignition switch, so the wire needs to go from the alternator past the battery,through the firewall,to the in-dash ammeter, out the other side of the ammeter, back through the firewall and to the battery (starter and solenoid are on the other side). I'd also thought that the 100 amp ammeter would be better up to the capacity of the alternater than the stocker as there was some concern that it might not be up to the task. My thought was that 57 amp alternator would fry a 30 amp ammeter if the only drain on the plus (+) side of the system was the ignition coil. I guess the capacity of the ammeter is only reached at high speed? You are right about the ability of the in-dash ammeter telling me anything. I'd thought that by leaving it hooked up or reversing the wires if necessary I could look at a dischare reading to tell if I had left anything on. But if it's all wired through the switch the problem it would tell me about would be more serious than something I hadn't turned off. Don't  know where you got the idea of my concern about under the dash but sometimes my fingers don't type what my mind means. GPster

[Skip]

The only reason you'd want an ammeter, or a volt meter, for that matter, is togive you the ability to monitor the charging system whilst operating the vehicle.

An ammeter under the hood does't tell you anything unless you're out under the hood looking at it.

A charging system needs neither an ammeter nor a volt meter in order to function properly  These two devices are placed in  the circuit so that you can monitor the charging system performance.

FWIW, I wouldn't worry about a 57 amp alternator frying your 30 amp ammeter.  You'd have to have the engine turing over at a pretty good clip whilst charging a nearly-dead battery to get the alternator to put out enough juice to peg the ammeter.

[GPster]

FWIW, I wouldn't worry about a 57 amp alternator frying your 30 amp ammeter.  You'd have to have the engine turing over at a pretty good clip whilst charging a nearly-dead battery to get the alternator to put out enough juice to peg the ammeter.

Thanks for that little bit of assurance. That makes it so I can understand it. Now if we can get Fat Cat to put this in the file Enjenjo and I won't be the only ones to have a copy of it. GPster

[GPster]

Today I ran wires from the engine compartment through the firewall and under the dash. I wired it to an after-market 60 amp ammeter and to a key/switch. It starts when I turn the key and on the second try the ammeter was wired to show a charge. Can't be any more than 5 amp charge showing on fast idle so I'm going ahead with the stock truck gauges. God, it feels good to have made some progress after so much time talking about it. GPster