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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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I do know that a healthy charging system should be measuring between 13 and 14v if you charging at 12.9v it will kind of sort of charge but if its loaded like running a cars electrical system that amount of charge can not keep up and the battery runs down slowly.
The charging system should be at the very least 1V about a good charged battery ~ 13.5V – 13.6V
If the alternator is tested below 13V under any load you have an issue.
Some vehicle charging systems are controlled by the ECU were the alternators output is set.Might suggest you have your battery load tested again along with the alternator.
I can tell you my vehicle with all off road lights running (3 sets of 55W) along with HID head lights and fog lamps, charging voltage never drops below 14V
Well I know the ECM controls the alternator on this car and I know the alternator(s) have been good, but it’s not putting out more than .2 volts over the battery charge with no electrical loads running. Radio is off, ac is off, fan is off, lights are off. My question is does anyone know the spec for the voltages that should be going through the red and gray wires from the ECM to the 2 wire alternator connector?
By the way, I swapped the alternator on this car with a known good alternator from another person’s car and it did the same thing as the other 2. Put it back on the cavalier it came off of, and it was charging. It just wasn’t on the car with the charging issues. So the problem has to be in the red or gray wires from the ECM, or the ECM itself.
Could the absence of heat protectors on the battery terminals / alternator terminals cause it?
looks like the battery should have a cover/shield over it too.
most auto part stores can test the alternator both on and off the car… I like the advance auto tester they have better then the autozone one… its the one that is black and till print out a paper showing a graph of the charging system on the car… but I would start and have them test the alternator and battery on the car then take them off and have them test each one at a time… they have a machine that will spin the alternator and test it by itself
I work at Advance Auto. So that’s how I got a lot of the numbers from my original post. The alternator will not charge when on the car, but it passes the test on our bench tester.
I had a 93 Accord that alternator tested good on bench test but under 13V when on car. After a lot of pulling my hair out it was a bad ground, the small ground wire that went to inside fender of car. I would suggest running a new ground from that and other grounds you can find.
I understand but after removing/installing alternator 4 times mine was a ground issue so just though it was worth sharing.
Thank you, I appreciate the input. At this point though, I just need to know if anyone has the specs for the voltage that the red and gray wires from the ECM to the voltage regulator should have with the car running. Surely someone has to have those. I have not been able to track them down over the course of many different google searches.
It’s probably ~12V.
Your issue is extremely chaotic and bizarre.
You don’t need to check voltage just disconnect the negative battery cable and check for open closed circuits between the alternator harness and corresponding ECM pin location. shake the harness to see if the circuit opens.
You might be able to slide some small pins into the corresponding ECM harness wire from behind to probe the circuit grounding the negative probe pin while the car is running. But don’t use the ECM ground use clips and ground it to the brake pedal or something.
You can’t test the alternator harness wires while the car is running they’re waterproof.I can probe the wires, I have a Power Probe 3. Does anyone at all know the actual voltage spec for those wires?
Provide me with as much info as possible and I will look in my data base. If you know wire color (any stripes) you know pin number from computer, car info such as model, engine, anything at all that could possibly used on a wiring diagram. I am more mechanical than electrical. Also if you have a pick a part yard near you……..carry a jumpstart for power then probe wires on car in junkyard.
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