Can any one tell me why I would have a thumping noise when i turn on my heat. I doesn't happen all the time, I guess when ever it feels like annoying me. But goes off when I turn on the a/c. I have on 01 s2000. Thanks

 

My WRX did this, but only when it was cold out. Obviously I didn't have my heat blasting on a hot day, but I tried it when it was around 60 degrees out and didn't do it.

 

Maybe one of the flaps in the ducts slamming into position.

 

cool just another noise to add to the car, I swear. I'm about to find away to get rid of all the creaks and noise that come from the interior of this car then I'll charge for it and be come rich.