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This is on a 2000 Chevy Cavalier with a 2.2. Been chasing a charging issue for my buddy. Said his battery died and had to get it jumped. He went to Autozone, the battery tested bad, so he got a new one. About a week later, happened again so he called me. Checked the battery voltage, less than 12 volts. Charged it up to about 12.5 volts, put it in the car and started it. Voltage on the battery terminals while its running is about 12.8. Checked the voltage at the charging post on the alternator and its about 12.9. Not much of a drop, so figure the cable from alternator to battery is good and think alternator is bad. Pulled it off and bench tested, tested good. Keep searching. There had been some wiring repairs to the starter wires, so I cut those and soldered and heat shrunk them. Checked and cleaned all grounds. Same results with voltage. Checked the resistance in the cable from alternator to battery, and it was good. Got a junkyard alternator for $20 as a test part. It was an ac delco reman that looked only a month or so old, it was super clean. Same results. Back probed the 2 wires (red and gray) that go to the voltage regulator with my power probe 3 (Only bought it due to ETCG, and I love it! Highly recommend!) and both were just over 5 volts. So my question is does anyone know the specs of what the voltage should be on those 2 wires while its running? I believe the only possibilities left are the red and gray wires from the PCM to the voltage regulator, or the PCM itself. Sorry for the novel, I just like to be very thorough in my description of what was done. Saves time in the long run. Thanks in advance for any help.
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The Voltage only comes from the Ignition not the ECM. It passes through a fuse box. The two wires on my Max are 10amps 12 V.
The ECM doesn’t connect to the Alternator.
I’m not trying to be rude here, but you haven’t helped my situation at all yet. You just keep describing it as chaotic. Yes, the wires go directly from the PCM to the alternator. If you think that’s too “chaotic” and don’t believe me, take a look at the wiring diagram I’ve attached. So please, if you don’t know, let someone that does do the replying. Earlier your suggestion was to tow it into a Chevy dealership. That’s not going to happen. So I appreciate that you want to get involved, but you haven’t helped me at all yet.
I could look at my All Data and see if that has it … I need to have your Car make model year and 8th vin digit
First thing to do, would be to confirm that there’s no voltage drop on the 2 wires running from the PCM. Not just continuity. It looks like it’s a 5V signal circuit, so if there’s the 5V PCM output (red) and the signal wire going back telling the system how much to charge. So even if you’re losing a single volt, it could potentially be enough to throw off the target output.
You mentioned that you tried a different alternator. If you can test it in the car that would be your best indication of what the 2 voltages should be. Ohter than that, by my estimates you should be seeing a 5V output from the PCM and 0-5V PCM input.
https://www.ericthecarguy.com/faq/solving-automotive-electrical-problems#VoltageDropTesting
[quote=”ChuckBus92″ post=169681]The spec I’m looking for is for the 2 wires from the PCM to the voltage regulator in the alternator. One red wire, one gray wire. 2000 Cavalier 2.2 engine[/quote]
I could not find what it should be on any diagram I have. Just wanted so say I looked. Keep me posted as I am very curious about electrical because its something I want to be better at.
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