I have 1990 cherokee xj
When i turn on my heater or air conditioner air only comes out of the defroster. No air comes out of vents. We took the heater valve out. When we blow thru it the valve opens and closes. So it seems to work. It worked fine until we replaced our overflow tank. Is there some vacuum hose we could have knocked lose that we are not seeing.

 

None of my HVAC equip works so I'm just guessing here...

Its probably whatever directs airflow to the defrost or vent or floor. Not sure if its cable or vacuum controlled.

 

It's vacuum All the hoses seemed to be connected. I know we are missing something.

 

I'm having the same issue. Only mine started after I moved the vacuum canister. Worked before but not now. Defrost only, everything seems to be connected. Hope you find the issue.

 

There is a vacuum hose that goes under the coolant bottle.

 

vacuum egg check the vacuum resevoir by the side bumper on the passenger side in the front

 

what goblinish15 said!!

i had the same issue, hose came off the conaster, would only blow as defroster. hooked it back up, perfecto!!!

i have a 94 and it was located behind the front bumper, passanger side. super easy to get to.

 

Had the same issue.....when I change my front bumper out, I move the vacume cannister to the engine bay, shortened the vacume line and reconnected.....Now my heater and A/C are working perfectly. So is the cruise control...all controlled by that stupid cannister.

 

Thanks everyone. We are still looking. We found one line that was wearing out. Not right one, but glad to fix it before it becomes a problem.