Everyday when I start my truck cold in the morning, the alternator gauge drops down and my lights dim. Then the gauge needle climbs back up and the lights go bright. This happens a couple times every morning. I recently heard a funny high pitch rattle noise that sounded like it came from the alternator at idle after I drove home the other night. Has anyone had an alternator go bad and have these symptoms? Thanks, Shima

 

Normal.....just the grid heaters cycling.

 

Ditto. The grid heaters pull huge amps and dim the lights and drop voltage reading as they cycle. Don't know about the high pitched rattle noise.

 

Sounds like a bearing going out. Remove the belt, and feel the for resistance while you spin the rotor. There is a website that carries new bearings (front and rear) and new brushes for $35. I found that out after I bought a new alternator from the dealer for $350.

 

How about a link to said Website...

 

I had a high pitched rattling noise in that area a couple of weeks ago and it was the water pump going out. it is right under the alternator.