GMC ac popping sound

Dear Barbara,

I have a 2010 GMC truck and every time I turn on the AC unit there is loud pop. I was wondering if you can tell me what it might be. I took it to the dealer and GM said that it was normal.

Thanks Ernie

Dear Ernie,

I have seen this a lot. What's actually happening is the compressor is starting to lock up. The popping sound is the AC belt tensioner slapping when the compressor doesn't turn. Take it to GM and make them honor the warranty.

Thanks for writing in,

BT