Alternator Problems

timkins · June 18, 2009, 04:49:52 PM

On my way home yesterday after a short cruise in the car, the alternator started overcharging again 16+ volts. This is the 3rd time this has happened in the past 2 years. It is a 3 wire GM Delco parts reman and the parts store told me there must be some other problem as this is not normal. I have checked all of the grounds from engine to frame, battery to frame and they are all good. My next step is to rewire the alternator. What exactly is the proper wiring for a 3 wire alternator. A diagram would be helpful.

38HAULR · June 18, 2009, 05:58:30 PM

Does this have an external firewall mounted regulator?. Or is it the three wire version with integral regulator, that has "Batt" Terminal with heavier gauge wire going straight to battery. "Ind" that goes to the dashlight which is fed from the ign switch. The third wire will be "batt sense".? This third wire determines the charge rate by sensing battery volts. This wire should be connected directly to the battery plus terminal to function properly. If connected further away,and you have some load on the system like an amp or driving lights,aircon etc ,it will pick up the voltage drop within the wiring system and increase the charge accordingly and operate erroneously in my opinion,. hope this gives you some assistance.......Frank.

34ford · June 18, 2009, 06:07:42 PM

Quote from: "timkins"On my way home yesterday after a short cruise in the car, the alternator started overcharging again 16+ volts. This is the 3rd time this has happened in the past 2 years. It is a 3 wire GM Delco parts reman and the parts store told me there must be some other problem as this is not normal. I have checked all of the grounds from engine to frame, battery to frame and they are all good. My next step is to rewire the alternator. What exactly is the proper wiring for a 3 wire alternator. A diagram would be helpful.

Here's a good site for some information'

http://www.madelectrical.com/electrical-tech.shtml

wayne petty · June 18, 2009, 07:07:53 PM

that is strange.... do you have a battery cut off switch?

is your battery bolted down so it cannot jump up and short out to the body//?

?

does anybody test the charging system by pulling a cable off with the engine running.. always a bad thing...

are the wires attached firmly... proper ring terminals... proper wire sizes...

been jump starting peoples cars??? with totally dead batterys?

if you have an external voltage regulator type.. is there a ground wire from the back of the alternator to the mounting leg of the voltage regulator...

once you post which type you have.. we all can provide more information...

enjenjo · June 18, 2009, 10:35:17 PM

Quote from: "38HAULR"Does this have an external firewall mounted regulator?. Or is it the three wire version with integral regulator, that has "Batt" Terminal with heavier gauge wire going straight to battery. "Ind" that goes to the dashlight which is fed from the ign switch. The third wire will be "batt sense".? This third wire determines the charge rate by sensing battery volts. This wire should be connected directly to the battery plus terminal to function properly. If connected further away,and you have some load on the system like an amp or driving lights,aircon etc ,it will pick up the voltage drop within the wiring system and increase the charge accordingly and operate erroneously in my opinion,. hope this gives you some assistance.......Frank.

If you bias the alternator at the battery stud on the back, you are taking a chance of it never getting enough of a charge to keep the battery topped up.

timkins · June 19, 2009, 08:05:23 AM

The alternator has an internal voltage regulator and yes there is a battery cut off switch mounted in the floor underneath the passenger site that has a couple of wires that bypass the cutoff switch for constant power to the radio and power door openers. As far as I can tell the wires are the proper size and connected firmly. No I have not had the battery disconnected with the motor running as the battery is located under the floor and almost imposssible to get at. I do not think the the sense wire is routed back to the battery and that it is connected in another spot. Not sure where as I am just inb the process of tearing the harness apart to figure it out. It might just be simpler to run a wire directly from the battery to the alternator and clip the other sense wire. Is that an alternative?

model a vette · June 19, 2009, 08:34:36 AM

Try using this:

timkins · June 19, 2009, 09:50:56 AM

I have just begun to check the wiring and found that the number 3 connector on the alternator has a loop in the wiring and is connected to the number 1 lug on the alternator. The wire connected to the number 1 lug then runs to the terminals on my voltage gauge and then continues to the battery. I guess I need to disconnect the loop and go dirrectly to the positive terminal of the battery. Is this correct?

wayne petty · June 19, 2009, 10:50:03 AM

the really nice thing about these internally regulated delco alternators...

they can be rebuilt in minutes.... with a set of nut drivers... and a spray stick out of a spray can...

most parts stores also have mostly complete rebuild kits...

the black picture will make the units work...

with your battery a few feet away... i would think running the output wire and the red wire on the plug all the way to where the battery cable connects... this is how they are supposed to be wired... but also with fuseable links to prevent harness fires... fuseable link sizing.. 4 numbers smaller than the protected wire... 12 gauge gets a 16 gauge fuseable link.. 4 inches long.. 10 gauge gets a 14 gauge fuseable link...

as for the white wire ... that goes to a bulb in the dash... with the other side hooked to switched power...

heavy duty rectifier bridges are available.. most of them come with 6- 25 amp 100 PIV diodes... the heavy duty versions come with 6 50 amp 200PIV diodes... (peak inverse voltage) this lets the diodes live longer as they can handle more power before failing...

why is all this important... if the alternator output wire looses contact with the battery... the output current has no place to go... so the voltage builds up in an instant before the regulator can reduce input signal to the rotor.... (think of a water hammer in the plumbing system) when this happens... the voltage can exceed the PIV rating of the diodes... it can also damage the voltage regulator... as it is protected.. but only for normal operating voltage levels...

now that all this is out... you can reduce your alternator failure rate by hooking the alternator output and sense wires to the battery side of the cut off switch... yes.. that will leave power running to the back of the alternator... but it will reduce the failure rate of alternators..

if you have to have the cut off for a sanctioning body... this won't fly...

one last thing... is the alternator bracket painted where the alternator case touches it... the alternator has to send power through its rear case where the rectifier bridge is mounted... through the case bolts to the front half of the case... to the alternator bracket.. to the cylinder head or engine block then to the battery ground cables to connect it to the battery... where there is paint in the way... the current is restricted ... that can also cause problems...

wondering about grounds... some racers have taken to grounding both heads to the distributer housing... reduces the length of ground circuit back to the distributer... but that is off subject...

ok. guys... i know i said too much.. or typed too much... but i like to type....

timkins · June 19, 2009, 02:56:21 PM

Well, I got under the car this afternoon and removed the cut off switch and then I grounded the alternator directly to the intake manifold. We'll see what happens now. I will keep you posted.

Mac · June 19, 2009, 07:35:44 PM

Quote from: "timkins"The wire connected to the number 1 lug then runs to the terminals on my voltage gauge and then continues to the battery.

I don't think you want the Alt output running thru the volt gauge, just direct to the battery. Find a different source for the gauge.

38HAULR · June 20, 2009, 10:29:55 PM

I was a bit misleading enjenjo in my wiring description,correct that the sense wire goes to Batt +ve. At the battery itself, not looped at the alternator,if I interperate the reason for your correction correctly.......Frank.

enjenjo · June 20, 2009, 10:45:09 PM

Quote from: "38HAULR"I was a bit misleading enjenjo in my wiring description,correct that the sense wire goes to Batt +ve. At the battery itself, not looped at the alternator,if I interperate the reason for your correction correctly.......Frank.

Well, you are forgiven this time, but if it happens again, I am sending SWMBO to give you a beating.

38HAULR · June 22, 2009, 01:11:36 AM

I stand "chastened" :oops: :oops: :oops: :oops:.. Frank.

Crosley.In.AZ · June 22, 2009, 08:42:37 AM

Quote from: "enjenjo"
Quote from: "38HAULR"I was a bit misleading enjenjo in my wiring description,correct that the sense wire goes to Batt +ve. At the battery itself, not looped at the alternator,if I interperate the reason for your correction correctly.......Frank.

Well, you are forgiven this time, but if it happens again, I am sending SWMBO to give you a beating.

will there be a public viewing of this?