About two days ago, I noticed that the air would only come out of the defrost location regardless of the air setting and fan speed. What could be the issue?

 

Check all your vacuum lines.

 

After posting this thread, I did some additional research. Just checked all the lines and the canister behind the bumper. Everything appears to be alright?

 

Except where they're corroded through behind the battery?

 

I checked that line... but I'm going to go over all the vacuum lines again. Might even try to make a smoker to smoke out the leaks lol

 

How's the vacuum source to the system from the intake manifold?

I always relocate the ***** to under the hood on the passenger side.

 

I did some research last night, and I need to take a look at the check valve. But upon visual inspection, the line going into the intake manifold looks fine, and the vacuum reservoir looked fine, as well. I will probably relocate the reservoir, once I fix this leak.

 

If you have a vacuum pump brake bleeder (Harbor Freight) you can run the system down and see if it holds vacuum. It only takes around 8 in/hg to operate the HVAC doors.


Hook up to the vacuum tap on the intake manifold (coupling with the check valve) with the vacuum pump and pump the system down and see if it holds.





Pump hook up on a '99 XJ....without engine installed :-)

 

So I found the leak and temporarily fixed it with electrical tape lol. Not sure how I missed it last night, but near the battery, there was a good size hole in the line. Now the air and heat comes out of the vents again. Where do you all recommend relocating the vacuum reservoir to under the engine bay?

While on topic though, I believe I read that the cruise control works on vacuum, as well. It has not worked, since I bought the Jeep last summer. No light comes on the dash either. What could be the issue?

 

I relocated the vacuum ball under the coolant reservoir near the firewall. Mine is a 1988 model though..

 

No kidding? Near the battery?

The same leak COULD be the cause of the cruise control being inoperative......

 

He has more room than you did in that area!!

 

Mine is a 95.. I'll have to go back and see if I can mount mine there.

Yep, right near the battery. Close to the opening where the line goes through and behind the grille.

Cruise is still not working despite fixing the vacuum leak. It must be an electrical issue of some sort

 

It does work on vacuum but if you don't get a light on the instrument cluster it may mean that the cruise switches on the steering wheel are defective. Does the Cruise annunciator light up when you turn the ignition switch to RUN, just before cranking?

 

I'll have to double check, but I'm pretty sure that it does not light up at all.