Like the topic says. I noticed in the garage when its quiet that if i turn the key on and the engine is off i can hear the alternator "humming". I verified that the sound is from the alt. It seems to be charging alright, i was just concerned about the "humming". Any thoughts?

 

I've never heard an alternator hum with the motor off. I suppose if it's charging o-k, there may be nothing wrong. It doesn't smell hot or burnt does it?

 

Doesnt smell burnt or hot, though i havent left it with just the key on for any length of time (may not want to do that if there is a problem!). Is there any thing in the ECM that could be causing this?

 

Not in the ecm, Have you checked the voltage output with the engine running? Should be around 14 volts.

 

I also had this problem, but I've never heard it before on any of the many GM cars I've owned.

I talked to a guy that's an engineer for an alternator manufatcurer, and he says it's a piece of metal that isn't secured exactly right inside the alt. He says it has no bearing on how the alternator functions.

Just for fun, I opened the alt just to take a look. I couln't find anything obvious, so I put it back together and it still humms and charges.

 

Your sure its not the electric fan?

 

Forget about it, the alt on my camaro has been doing that for about a year and works perfect. Yours isn't a reman by chance is it? That's what mine is.