HELP, with HVAC issue?????

[JDawg965]

O.k. So I am new to the forums long time
Ready first time poster. I recently bought a 97 Grans Cherokee Laredo 5.2. My issue is that my heat/air will only blow through my defroster? Now I know everyone is going to say its a vacuum leak but I am pretty positive it's not, I replaced several cracked lines and cruise control works fine which I am told it would not work if there was a vacuum issue. So here is what I know. I did have lights on the controls (manual) 3 knobs when I bought the jeep after I removed the panel and put it back together the HVAC controls are the only think in the jeep not lit up? I pulled the controls out and there are two connectors one one each side plugged in electrically. Then in the center are the vacuum lines. When I turn my center knob (selector for air flow) it doesn't feel like there is any pressure at all easy to turn no tension air either on or off?? I also noticed on the back side of the HVAC. Controls there are silver taps that look like something connects to them? I dug around in the dash for a while and never found anything. I attached a picture at the bottom.

I have been struggling with this for a while and now it's starting to bug me.. Let me know any help would be great thanks

 

[TerryMason]

As you mentioned, the blend doors are operated by vacuum. When there is a partial or total loss of vacuum, the system will default to defrost.

I really think you've got a vacuum leak somewhere.

 

[JDawg965]

Where is the best place to check? I thought I got all the lines fixed up. Any way to test vacuum? I have cruise control which I thought works of vacuum? Let me know thanks

 

[TerryMason]

I did some searching on the net, and found this (for a 2001 GC)

Remove the right front head lamp assembly and check for vacuum.



If the vacuum is ok then pull the a/c-heater control head and check for vacuum to the control head:

 

[jeepjeep!]

I did this a few weeks ago, i swore it was not a vacuum leak. Well turned out it was. Does your cruise control work? Its run by vac also, The most common place is behind passenger headlight like Terry said. Mine was rotted! Worth checking it was a $2 and 10 minute fix. I had lost my cruise control and no matter the setting air always blew from the defrost position.

 

[JDawg965]

Yea I checked behind the headlight I will check again, the cruise control does work. That was the first thing I tested it just seems weird there is no resistance on the selector knob at all??? None u can turn it easily, no clicks nothing??? Still trying to figure this one out

 

[jeepjeep!]

Maybe take the knob off, could ne broken and its still on defrost? ??

 

[JDawg965]

Everything moves in the back of it when I have the cluster out? I just can't figure it out!! My next thing is I may smoke test the vacuum lines bc maybe I have enough to make cruise control work but not enough to adjust air flow?

 

[jeepjeep!]

Maybe so, did u check the line that runs under the battery? Its plastic