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· PrOpeller
706 Posts
Discussion Starter · #1 ·
I'm at my wit's end with this one and hoping somebody has a clue what might be going on here...

Alternator is overcharging battery at 17+ volts. This is confirmed by my digital voltmeter at the battery and at the alternator b+ terminal. Also, my dash ammeter pegs to 30+ when I rev the engine up.

The problem CANNOT be the voltage regulator, however. I've tried several confirmed good ones and even tried a brand new one with no change. I have also replaced ALL wiring to/from the alternator and voltage regulator and have verified proper gounding of the regulator. I have checked/replaced all my grounds (frame to block and alt to block), and I have cleaned and verified battery terminal connections and fuseblock connections.

Is it possible that there is something wonky inside the alternator itself? Or, that my dash ammeter has shorted somehow to cause this condition?

The car is a 1.1L GT.

· PrOpeller
706 Posts
Discussion Starter · #3 · (Edited)
oldopelguy said:
Just a quick double check, it is an alternator, not generator, right?
Yes, alternator.

First step would be to run the car with the plug pulled on the regulator, just to make sure it doesn't charge. If it does, then bad alternator.
Strike one...cranks out mucho voltage.

Second step would be to double chack the maximum output of the alternator and compare it to what you're getting. This is done by jumpering the D+ terminal on the alternator to the DF terminal, usually with a little jumper wire with 2 male 1/4" spade terminals jumpering the red wire to the black one on the regulator plug. It should peg to a voltage even higher than what you currently get, if not, probably bad alternator.
I had actually tried this one before per the FSM. It pegs the voltage same as before. Strike two.

Last check, to isolate it down to pieces/parts, is to make 3, 8" jumper wires...
I'll try this tomorrow, but I think I know what the result will be.

Or, if you're just plain tired of all this, swap out the alternator with one of these: http://www.partsamerica.com/ProductDetail.aspx?mfrcode=ATR&mfrpartn.
Nice option which, unfortunately, is not available in this case. It appears the GT1100 has a slightly different case than a standard Opel 1.1L alternator. The mounting ears are in different locations.

That's the main reason I just had this one rebuilt locally. But the shop that did the work was sure it had to be my wiring since "there's no way an alternator can put out too much voltage with a functioning regulator." I didn't believe the guy when he said that, but supposedly he's the expert, right?

Many thanks for the advice, OldOpelGuy! Now I know I'm not going crazy, and I will bring the alternator back to have the diodes checked. Hopefully, I won't have a problem getting it repaired correctly this time. :rolleyes:
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