Ammeter Question

[Clark K.]

My '65 L76 A/C Coupe has the factory ammeter. Since I am having to charge my battery after every drive, I suspect that my alternator is not putting out enough amps.

When I am running my power windows or moving the headlight buckets, or I have the headlamps on, the ammeter shows a slight deflection into the negative range. The ammeter never shows a reading in the positive range. Does this reading on my car's ammeter indicate that my diagnosis is correct?

If so, where do you recommend that I send my alternator in order to have it rebuilt to the exact factory specs?
-Clark

[Michael W.]

Re: Ammeter Question

Could very well be the regulator or wiring- a simple bad ground will cause the described problem.

[Tom K.]

Re: Ammeter Question

Clark, I would start by checking the voltage with a digital voltmeter. With the engine running it should be 14.0-14.6 volts at the battery. Checking the voltage will eliminate the question of what the ammeter is showing. There is a possibility that you could have bad diodes in the alternator or as mentioned a defective voltage regulator.Hope this helps.
Tom

[William C.]

Re: Ammeter Question

Amen to the post on Voltmeter check at the battery to verify the charging system. There are many posts in the archives regarding the ammeter system in the '63-67 Corvette and the fact that is not a direct reading system, and therefore unreliable for troubleshooting. Look at the charge across the battery terminals at about 2000 rpm and you will have your answer as to the alternator/regulator function with respect to the charge.

[Carl N.]

Re: Ammeter Question

Clark,

Really sounds like you have an open ground. Check your glove box light, interior lights and so on.

Also if you have a correct date coded alternator you may wish to consider a cheap rebuilt from Auto Zone - Advance Auto ect. You could install it and see if your problem goes away - same with battery - if it keeps draining down you will need to find the source of the drain. Put your date coded back and save it for judging.

Carl