Gremlins in my heating system

[briwayjones]

While my heat is on and I'm at idle (not sure if it does it while moving, to loud to hear) I get a thumping sound and can also feel a slight vibration through the pedals and floor. If I turn the heat off it goes away. At first I thought it was the blower motor but adjusting the fan speed doesn't affect the thump. It also sounds like it's coming more fromt he middle of the engine bay instead of the right side where the blower motor is. Turning the heat off seems to be the only thing that affects the thump.

 

[budwich]

do you have your air flow set only to "floor" type circulation. The other positions which combine with the upper air flow cause your air compressor to turn on for some period of time to help dry the air... maybe this is what you are hearing???

 

[briwayjones]

I think it only does it when it's on floor only. I'll have to see if it'll do it when it's on defrost or another setting. If you're refering to the AC compressor coming on it's not that, I'm familiar with that. This isn't a click like that. This sounds like you're hitting a drum.