Loud Thump When Changing Heater Positions

[ZeroCool84]

Hello all,

My 2006 Liberty started something... "new" this winter. When changing heat positions (like moving from defrost to floor to vents, etc...), I'll get a single loud thump coming from the passenger side dash area. I'm talking noticeably loud, almost like hitting a speed bump or *** hole going too fast or something like that. This isnt our primary vehicle (meaning it doesnt get driven daily) and I usually drive it myself but my wife heard it for the first time today while we were at a standstill and I changed to defrost and was like "what the heck was that!?", which reminded me that I should probably look into it

It doesnt happen every time I change positions but seems to happen almost every time I change the position for the first time from a cold start.

Thoughts on what this may be and any reference on how to troubleshoot/fix this myself? I can live with it... just worried that its the first warning signs of something more significant/expensive about to break.

Many thanks in advance for any/all responses!

 

[Johnny O]

Sounds like the vent damper is slamming hard. Does it only happen when swapping from low(foot zone) to higher up (dash, defroster)?

 

[ZeroCool84]

Sounds like the vent damper is slamming hard. Does it only happen when swapping from low(foot zone) to higher up (dash, defroster)?

I usually go from low to high or high to low when I change positions so I would say its probably a safe bet to say yes. I'll do some more testing tomorrow.

If it is the damper, what would be the "fix" to something like that? Again, it only seems to do it ones per cold startup as of right now. Concerned that it will start doing it more frequently and/or just break.

 

[ZeroCool84]

So of course I couldn't get it to happen driving today... sigh. It only seemed to start doing this when it got cold outside and today is a cold one so not sure what stopped it.

Maybe threatening to fix something caused her to self correct...

 

[Johnny O]

So of course I couldn't get it to happen driving today... sigh. It only seemed to start doing this when it got cold outside and today is a cold one so not sure what stopped it.

Maybe threatening to fix something caused her to self correct...

I had/have this problem, though not as loud as you described. On my 07 the vent positions would clunk at random between positions for both heat and AC. I found the stupid micro pneumatic vent position control had dried out. I cleaned it with alcohol, careful to not get anything in the holes, then treated the rubber seal with silicone grease. This solved all my vent position and control issues. However after it sits overnight in the sub arctic cold, it still clunks before it is warmed up.

I am not certain which KJ model years have the micro-pneumatic/vacuum system and which are fully electromechanical like the KKs.