So my dad and i were driving down the road tonight and i felt and herd a couple of thumps on the passenger side. We turned the heater off, and the thumps stoped. Did a search and didn't find any thing. Anyone got any ideas?:confused:

prbably a temp door or recirculate door from the actuators. A common problem and can be reprogrammed and fixed sometimes.

I'm curious about the 're-programing'...........mine is doing the same thing.
I suspect that the average tech. at G.M. won't be familiar with this???

me too...

Most dealers should know about it.
You can reprogram manual or automatic air with updates.

Did you have the defrost on?

It could be the sound of the A/C compressor cycling.

My 01 truck makes the thump noise too. In the summer it affects the air flow through the AC outlets.

:banghead:not sure if it was on. we just hit the auto button to see if it was the heater, we didn't look to see if the defroster was on :banghead: