Anyone with vacuum hose expertise please chime in -A/C HEAT

[diablokicks]

So my TJ 99 wrangler has an issue with the heat/ac defaulting to the defroster, and from earlier posts i think you all helped me determine that it is a vacuum hose issue. I'm getting sick of putting up with it and want to try to fix it. I have a 4 day weekend coming up next week and would like to try to tear the jeep apart and see if i can find the problem. Please chime in with anything you know about vacuum hoses, the routing of them in TJ's, what i should be looking for, where i should look etc. Really anything is useful.

 

[RockChucker]

when mine defaulted to defrost, it ended up being super simple. i pulled the control unit out thinking the little vacuum manifolds were plugged. it ended up being me breaking the vacuum hose that comes off the back corner of the intake. i would start with the obvious before you commit to tearing your entire dash apart.

 

[Fuller]

Usually it will be something simple like a cracked line in the engine compartment or needing to add a check valve in line on the source hose. i know on xj's the line ran under the battery and would get battery acid spilled on it causing a hole.

 

[Cherokeester]

There was a fix for this published in JP magazine some time ago. I will see if I can dig it up. I believe it could be more than one thing causing the problem but it is most likely what they wrote about.

 

[Cherokeester]

Here it is, this should take care of your problem.

http://www.jpmagazine.com/techarticles/electrical/154_0801_jeep_wusses_quick_heater_fix/index.html

 

[diablokicks]

There was a fix for this published in JP magazine some time ago. I will see if I can dig it up. I believe it could be more than one thing causing the problem but it is most likely what they wrote about.

From that article it sounds like it would blow all the time from the defrost. Mine will blow from the vents at lower RPM's, and default up to the defrost once i hit the higer RPM's. Do you think that this could still be the problem?


Does anyone have a diagram of where the vacuum hoses run?

 

[DAA]

Mine will blow from the vents at lower RPM's, and default up to the defrost once i hit the higer RPM's.

I haven't read the article, but my Son's ZJ was doing the same thing. It wasn't even so much an RPM thing as a load thing, any time the engine was under load all the air would come out the defroster. I just started following the vacuum line around the engine compartment and found a hole in the elbow coming off the line going to the cruise control. Fixed that leak and that fixed the problem. His cruise still doesn't work though.

Long way of saying, what the guys above have already said - I'd start by checking the vacuum line in the engine compartment.

- DAA

 

[Bart]

Yes, it will still be a vacuum line, but most likely a crack. Like has been said I would start in the engine bay and follow every line. Concentrate on any that are close to heat sources or may be rubbing somewhere.