1973 Z/28 - Ammeter at full charge - Team Camaro Tech
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post #1 of 3 (permalink) Old Jul 24th, 18, 04:44 PM Thread Starter
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1973 Z/28 - Ammeter at full charge

Hello - I know this is about a second gen Z/28 but I couldn't find a better place for it. I've owned this car since it was 3 years old and have never had any electrical/charging problems. This morning I started it and the ammeter immediately went to pegged on the right (as if max charging). As the car idled, the gauge slowly started to move left until it was just under the "+40" mark on the right but didn't seem like it was going any further. The alternator is the original and after some research I thought for sure that I lost one of the diodes in the voltage regulator and I would be replacing the alternator. I have an O'Reilly's Auto Parts store near me and they tested the battery and the alternator out of the car. Both passed which, again, surprised me. With the car idling and no accessories on, I measured 13.54 VDC across the battery terminals and measured 14.10 VDC between the negative battery post and the post on the back of the alternator. From what I've seen this seems good but I'm looking for input from someone who has experience with this type of problem. Can a device further down the line (i.e. radio, lights, etc.) cause this? Is this going to be "pull a fuse one at a time until you find the problem?"

Any help is appreciated...thanks,
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post #2 of 3 (permalink) Old Jul 24th, 18, 05:52 PM
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Re: 1973 Z/28 - Ammeter at full charge

Why not just replace the voltage regulator, and also the diode trio and brushes while you're in there. Many replacement alternators have a habit of being low quality.

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post #3 of 3 (permalink) Old Jul 24th, 18, 06:21 PM
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Re: 1973 Z/28 - Ammeter at full charge

Originally Posted by debarba View Post
I measured 13.54 VDC across the battery terminals and measured 14.10 VDC between the negative battery post and the post on the back of the alternator. Any help is appreciated...thanks, Bob
Measure: between battery post and its clamp, and neg post to alt case.
You show 0.6 volt difference and should be no more than maybe 0.2 volts.
I would remove both ends of both cables and wire brush the bejesus out of them. Same with alt red wire on post AND on horn relay buss bar, and in fact, put both wires on the same screw on buss bar.
The OE ammeter is actually a millivoltmeter as the gauge is hooked up between the horn relay buss bar and battery junction block next to battery - follow red wire pigtail from clamp.
I would also get a Harbor freight ammeter, $5, maybe $10, and wire it between the battery supply wire and buss bar.
This set-up will show battery charge/discharge
Compare results with OE gauge.
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