Charging question

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August 30, 2008, 11:10:36 AM

Here's my question. I had the alternator rebuilt in my 72 Dart the other day because the bearing and pulley was damaged. I noticed the last time i drove it that my dash guage was showing a negative charge. My battery shows 12.63 volts with the car off but when i start it the battery shows about 11.63 volts. If I pull the negative cable, the car immediately dies. What do you think? Volatge regulator?? I'm no electrician (I'm a plumber).

Thanks in Advance

Scott
72 Dart

The charging system is not working, but it could be the wiring, alternator, or regulator

You said with the motor off the battery was 12.63. It should be at least 13.8 if its up to snuff. I would replace the battery first, then if you have any more problems, at least you know the battery is not the problem.

if he starts it and it reads 11 volts then its not charging.. get the thing to charge first then worry about if it needs a new battery...

check all your grounds, all your wires make sure none is broke. most likely is the regulator.. do the alt and regulator match?

12.6 is the correct voltage for a six-cell lead-acid battery at rest with no load. The battery is not the problem.

Quote from: abodyjoe on January 11, 2008, 09:16:32 AM

I believe it's has the original voltage regulator. It's black with yellow lettering. The car is a 33k mile survivor. I'm sure it's the regulator. On the day it quit charging I had just finished recharging the A/C. I was driving the car, switched on the A/C and i noticed then the guage on the dash show a negative charge. Maybe the regulator got fried then? IF I cut off the A/c or even pull the fuse the the compressor there is not change still not charging.

To check the alternator and the regulator connect a voltmeter to the battery, start the car and:

Single wire field alternator: disconnect the wire from the regulator at the alternator (small green wire) and put a jumper wire from that terminal to the alternator's output post (thick red or black wire) to the terminal you just disconnected. This "Full fields" the alternator (tells it to give all it can) as this system regulates (meters) positive voltage to control the alternator's output.

If the voltage goes up the regulator is at fault or it's wiring but the alternator is good.
If it doesn't, the alternator is bad. If there is a large spark and/or it freaks you out because it is sooo loud and it melts the terminal, the alternator is shorted internally and has probably killed the regulator in the process.

Dual (two) wire field alternator: disconnect one wire and test it for positive (+) voltage. If test shows it is hot (+) reinstall it and remove the other wire. Put a jumper wire from any ground to this terminal where the NEGATIVE wire used to be. This "Full fields" the alternator (tells it to give all it can) as on this system it regulates or meters teh NEGATIVE to control teh alternator's output.

If the voltage goes up the regulator is at fault or it's wiring but the alternator is good.
If it doesn't, the alternator is bad. If there is a large spark and/or it freaks you out because it is sooo loud and it melts the terminal, the alternator is shorted internally and has probably killed the regulator in the process.

Also, check the case grounds for both types of regulators as they ground through their mounting screws. Corrosion or paint can interfere with the connection to ground and stop the regulator from working. (Ignition ECU's have this issue too.)

Good luck

Quote from: PureGTS on January 12, 2008, 12:39:09 AM

Great post thanks for the tips.

Scott

it was the voltage regulator. I guess 35 years of life is all it had in it!

There is a electronic regulator that is available that looks just like and connects the same as the OEM black box type, but has electronic guts. You can tell it from the others by looking at the back of it and there are no old style white fiberglass packed coil winding(s) (resistors). I just haven't found a source for them yet. I usually get them from junk yard cars and they've all been good too. I've found them to be able to handle the 65 amp alternators by only modifying the alternator itself. And that's a really easy swap and mod' too. Just ground one of the two field terminals and install it. Done it many times. Great for electronic ignition, A/C or big stereo cars.

Great i like the idea of having a original looking regulator because my car is a survivor and has almost all of it's original pieces. I didn't want to pay NOS prices, plus I wanna drive the car not park it in a parade field.