Last Friday, I was driving with my headlights on. After a few minutes, the radio went dead. I turned the headlights off, and the radio came on. I turned the headlights on again, and the radio went dead. After that, I drove with the headlights off. I assumed the problem was the alternator.
This past Tuesday, I took the car to my regular repair shop. Wednesday morning, I called, and they said the problem was the battery, and they put in a new battery.
This doesn’t make sense to me. I hadn’t had any trouble starting the car, which I thought I would if the battery was low. As long as the car was running, shouldn’t the alternator have kept the battery charged, even with the headlights on? And after I turned the headlights off, the alternator seemed to recharge the battery with no difficulty. Between Friday and Tuesday, I had no problems with the car (I never used the headlights). It started OK and it ran OK.
“This doesn’t make sense to me.” – And it doesn’t make sense to me either. You probably had a perfectly good battery and alternator, but some freaky glitch in the wiring occurred. The shop couldn’t reproduce the situation, but shrugged and got a battery sale out of it. You are not of the woods yet. The glitch may recur at any time.
I agree with Steve…Something like a bad body ground anywhere in the system can cause this, or a bad connection in the fuse block that causes different voltages to drift through your cars electrical system…If you are lucky, they may have cleaned up some connections during the battery installation process and solved the problem. If not, I suspect the problem will return…
I agree with what the others stated about a ground issue. If the trouble returns check and clean the battery to chassis and other chassis ground connections.