My heater is stuck on defrost. I don't know where to start looking. Everything else works blend, and blower hi lo. When I move selector to heat vent or max it only blows out defrost

 

check the vaccuum lines under the dash on the passenger side, trace them back through the firewall to the vaccuum bucket and look for leaks/breaks. the system is vaccuum actuated that moves air from foot/defrost/etc.

 

My old XJ did the same thing. Replacing the heater control valve fixed the problem.

http://www.oreillyauto.com/site/c/de...+control+valve

 

X2 check this before you go throwing parts at it. I had the same issue a few months ago, turned out when I took my bumper off to replace something I ended up pulling a line loose.

 

Something else to look at is the vacumm lines go under the battery tray and the lines get corroded there and break...at least on mine.

 

Why has nobody asked if he removed the vacuum ball? Lol

 

OD, you beat me to it, buddy!!! Like be said. the 95 and older XJs (I'm sure if the 96 and newer are the same way) have a vacuum ball or cannister inside the passenger side of the front bumper. If you or the PO removed the front bumper or the ball can be ripped out by getting crazy offroad, chances are the vaccum ball is gone and that is definitely your problemo.

 

I moved my vacuum cannister inside the engine compartment when I put my aftermarket front offroad bumper on. It fits really nice on the back side of the passenger side wheel well right next to the heater blower motor. I never even had to fasten it to anything. The Jeep has been on it's side twice and the thing has never moved from where I put it.

 

I took out my vacuum cannister on my jeep 2 years ago pluged the lines and my heater works fine in my 93

 

you must have a magical jeep.

 

then again my jeep doesnt have anything else that really draws a vaccum. other than the brake booster and MAS.

 

Does anybody know where the valve is that actually controls where it flies the air too

 

At the heater control.

 

Further explain please. Is the valve behind selector on dash?

 

Yep