About a week or two ago, when driving home, my battery light flicked on while at a stop light. Also, as the light wen t green and I accelerated away, I noticed a kind of ‘whine’ from the engine, like a turbine spinning up. By the time I got home it was fine again and the light out, and has been until today, when it happened again…I noticed that it happens if I have the AC on and I’m at a stop. If I turn off the AC when waiting at traffic lights, that seems to eliminate the battery light, but I still here the whine. Any ideas?
The first thing to have done is have the battery/charging system tested. Some auto parts stores will do this in the parking lot for free.
A bad diode in the alternator will cause exactly the symptoms you are experiencing. The whine is from your alternator. Tester is correct about having your battery/charging system checked.
I think it is time for a new battery, get it tested as advised above. Then if you continue to have problems look at the tensioner and belt. Very simple and not expensive either way.
The alternator on my 2000 Blazer started to whine after I installed a battery cut-off switch. The switch wasn’t making a good connection. I removed the switch, cleaned the battery terminals, and reinstalled the cables. The alternator has been fine since.
First check/clean the battery terminals. How old is the serpentine belt? I replace mine every 3 to 5 years. As Tester suggested, have the battery and alternator checked.