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I can't get my charging system on my 76' to work properly. I have already replaced the alternator and the voltage regulator. I have also tried replacing the battery. It only charges at 12.2 volts at idle, and at about 13.2 when I rev the engine up.

It works fine for day driving, but if I drive at night, the battery goes dead after about 30-45 minutes because it can't handle the extra power draw from the headlights.

I have had the charging system "tested" at Auto Zone multiple ties, and they always say it is working fine.

This is really starting to annoy me, and I really have no idea where or what to look for to fix this problem.

If anybody has any idea what the problem could be, I would much appreciate any comments. :)
 

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The diagnostic tester they have can't really find problems in systems that are operating an that middle grey area.

I'm guessing that the charge light doesn't come on or you would have mentioned that.

I see a few things that could cause this:
Poor engine to body ground. Normally tied from battery negative to engine block, and battery negative to body ... but many times these get removed as mechanics fumble with their large stubby fingers.

Poor Alternator "A Terminal" to Battery Positive connection. Notice that this is fed through a fusible link that is often known to cause problems.

Bad "F Terminal" feed from voltage regulator to alternator.

Things to look for:
Using a voltage meter, the voltage drop from the alternator "A" to Battery Positive should be very small (Less then 0.5 Volts)

The voltage at the "F Terminal" should raise as the load on the alternator increases.

If you still can't figure it out, then there are other options. Several articles are "upgrading" to later internal regulated versions have been written. Some company makes a bracket for the standard 10SI GM alternator.

ConorP
 

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Agree w/ ConorP that likely a connection problem. Continuity check all the wires from the regulator connector to the alternator, and any other components that they run to. (See diagram in your FSM). If these connections are bad, even if you do a conversion, you will still likely have charging problems, since the original wiring is still used in most cases.
 
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