I have a 97 Blazer that is giving me another problem. Recently I have started hearing a whine coming from under the hood that changes with the speed of the engine. I have also noticed that the volt gauge will stay above 14 volts as I drive but when I stop and the engine idles, the gauge drops to around 10 especially if I have the lights on. I just put a new battery in earlier this week because the cold killed the old one finally. I'm pretty sure it is the alternator, I just haven't seen one behave like this before. Does anyone have any suggestions?

Chris

 

Sounds like the alt to me. I have heard of the alt whining, and what you describe with the charging, and when you are not accelerating and just idling, and then it dies with the volt gauge dropping, I would get an alt.

 

A) check the belt tension.
B) check the voltage at the field terminal with the key on engine not running. Should be 7 plus volts.
C) if a and b are good remove the alternator.
Don't buy cheap, they're junk.