Cobalt60

I was driving this morning before sunrise. I noticed the dash lights were off. At the same time I noticed the headlights were off. I though great the light switch in the cluster has gone bad now. The fog light switch went bad last year.

Then the car stumbled as I gave it some gas. Then I was coasting. Then a little resurge, then nothing. Coast off the road into a parking lot. It won't start. Just the low voltage clicking sound from the starter. Uber home.

I get some tools and go back to the car and pop the hood. The alternator belt is still there and appears ok. Battery connections look fine. The car starts right up and runs. The ABS light flickers, but then the ABS light turns off. This feels familiar. When my alternator went it did something similar. No warning lights lights on the dash.

I pull the battery. Figure I can charge it up and at least get the car home to work on it. At home I check the voltage. 12.1 volts. Doesn't seem too bad. It's on the charger now just to top it up.

This leaves me scratching my head. If it was the alternator the battery should be completely run down. The voltage doesn't seem very low. I replaced the alternator two years or so ago. Battery at the same time. Everything "should be" ok.

I'll drive it home this evening hopefully and go through it in more detail. Just looking for some thoughts based on limited information.

Cobalt60

So, I got the battery charged back up and reinstalled. Started right up. Checked the voltage with the car running. 14.1v which isn't bad. Drove it home, checked it again running. 11.8v.

Given the last voltage reading it seems like the alternator is bad. Weird that the first one was ok. Frustrating that it hasn't been long since I replaced the alternator.

Anybody have anything like this?

Cobalt60

I pulled the alternator and had it tested at Autozone. They checked it twice and said it was fine. The only thing I can see on the alternator that's unusual is that the inner nut on one of the connections was loose.

Hate to put this thing back in without understanding what's going on.

Cobalt60

I put the alternator back in. With the car running all I'm seeing is battery voltage. Occasionally it will come up to 14v. No idea why. Doesn't seem to change with rpm.

Belt is tight, no slippage.

I guess I could pull the alternator harness and check it for integrity. It looks ok, but maybe there's something I'm not seeing.

Cobalt60

Pulled the alternator out again. I'm getting faster. 20 minutes now.

Had it checked at a different place. All good. They checked it six times.

Checked the wiring. All seems good. At the alternator: Voltage across the plug in connector is 12.2v. Voltage across the B+ wire to ground wire is 12.2v. Battery voltage is 12.2v.

Car starts and runs fine. I just don't get the right voltage with it running at the battery or at the alternator.

Maybe there is a ground somewhere outside the charging system??

I'm going to put in back together and take it for a drive. If anybody needs their alternator changed I can do it pretty quickly.

Cobalt60

I got it all back together. At this point I've ruled out the battery, the alternator and the wiring between them.

I did notice that the voltage drops sharply when I turn the ignition switch to on without starting the car. Must be a ground in a system that's energized with the ignition on. Maybe the starter??

Cobalt60

So after all that it was the alternator.

It tested good at two different places, but I finally took a spare one down to a local shop and had it overhauled. Put the overhauled alternator in the car and 14.3v at idle. No idea why the other one tested fine, but wasn't.

Worst part of the alternator replacement is getting the top bolt in and the nut threaded. Otherwise it's not too bad. Less than two hours work. About an hour the last time. I did the roll the sway bar - remove the lower hose mount way.

If anyone wants an alternator that has passed multiple tests at multiple places let me know.