I have a 07 FX4 Screw and I started to notice that I hear and feel a thump or knock when I turn on my air conditioner. It doesn't happen all the time but I can make the symptoms repeat. It seems to knock the loudest if I am at idle and then turn on the ac but it wont happen if you just push the AC button in and out. The ac has to be off for a minute or two before it will knock again. Is this normal?

I did search the forums but for one air conditioner thread there were 20 leather conditioner threads and only one thread came close to what I was describing and someone suggested that is was a door or valve opening but that it shouldn't be audible.

Any advice would be appreciated.

 

Idk about you but I keep my a/c at 60, and when i turn it up to 74+ I will hear like a fan or a belt or somthing near the glove box start to grind and slow down. Not a metal on metal grind, but a maybe rubber on plastic or somthing.