I have found in a few vehicles - including my Ranger I drive for work - that when running the HVAC at idle, there is a clear, repetative bumping noise comming from the engine compartment. Today I experimented with this mistery bump while defrosting the windows in my Ranger work truck. The bump comes whether the truck is in gear or not and it happens whether I am givinng it gas or not. I've never noticed this in one of my own vehicles, so it's got me wondering if there's something wrong in the vehicles where I have felt this. Any ideas?

 

ac engaging?

 

Yeah it blows out cold air. The bump seems to come about every 20 seconds or so. I've got the hvac on now.

 

I think its just the compressor turning on and off on its own

 

i second the compressor. i know if i have my ac on i can feel the system running and vibrating. i can also hear that tick or bump of the compressor turning on/off.

 

Its just the compressor kicking on/off

 

I can hear the clicking of the A/C clutch.

 

Huh... I guess that's what happens when you cut the purple wire on your HVAC, ha. I haven't had AC in my truck since doing my body lift however many years ago, where my pulley ate through the AC line.

 

mine does this too but my AC still works.

 

if it cycles to much you could be low on freon

 

My 2006 has clicked like that since it was new. It's the compressor cycling