Bumping while using HVAC - normal?
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?
2004 Ford Ranger Edge manual 4.0 4x4 with 3" Body lift, 33x12.5 BFG A/T KO's, on Eagle Alloy 057 rims, and alot of mods
2011 Ford Mustang GT 5.0 manual with no mods yet
2005 Ford F250 automatic 5.4 4x4 with no mods