I just bought a 2000 Jeep Cherokee Sport 4.0L for my son. For it's age, it's in great shape, but one thing I noticed the other day is a squealing noise when the AC is on and I move the vent dial to the recirculation position.

I removed the glove box and I can see a small arm push what looks like a piston down into a cylinder. When the piston hits the bottom, the squealing noise starts.

I'm sure it's nothing huge, just annoying to listen to. Any ideas on what could be the cause and how to fix?

 

Since the climate control system is operated with vacuum the noise you are hearing is a small vacuum leak due to a leak in a fitting or seal for the damper operating ram....
Spray a small mist of water in the area of the noise to determine if the noise is coming from the ram or the fitting. You might be able to push the hose in to the fitting, but if the ram seal is leaking you probably will need to replace it.

 

It could also be that the AC compressor is going bad, and the serp belt itself is actually making noise.

 

The OPs description is a little vague....
Is the noise coming from in the cabin or the engine compartment....?

 

This was the first thing I thought as well. Hard to tell from a vague description. Pop the hood and see if its coming from the front of the engine. If so, its the serpentine belt. Compressor bearing could be going, belt could be bad or just loose.

 

It's in the cabin only, not under the hood. I took the glove box off and can hear the noise clearly inside the cabin once I engage recirc. The compressor sounds find and the belts are in good shape as well.

Thanks for the responses!!!

 

Best guess is a vacuum line. Does it blow cold alright? Everything is working fine except there is "a funny squeaky sound"?

Mines a '99, but I have that same cylinder thing right under the dash and I believe an actuator for the vacuum system and one of the doors. Maybe the door is jammed or broken causing it to work hard.

 

Come on Fellas, wake up. The man who posted the question is no dummy, he knows what he is doing.

He heard the sound coming from inside the cabin, particularly in or around the glove box location. Therefore, he removed the glove box and observed and heard that the squealing noise began when the piston hits bottom. Pretty definitive to me.

Webb

 

The description was well defined and based on a factual observation and inquire conducted by the owner of the vehicle at the time the sound was heard.

 

If it has Auto Temp Control, there is a solenoid that can cause a sequel.

Ron

 

 

I also have the same squealing noise when I use my heater, it's very annoying!

 

When using defrost?

Is the squeal coming from under your dash or under your hood?

 

lenglish, it sounds like the heater fan to me. When the recirculating door opens you get more fan noise coming through. Mine has made a similar noise far the last year.
Don