A-mac

I have a 94 XJ. all it will do is blow out of the defrost. it will change from cold to hot but just wont come out the vents. i know it is vacuum controled but dont know where to start lookin. point me in the right direction PLEASE!!!

ZINGGG

Is your heater hooked up? Mine does the same thing. But my heater isn't hooked up. The hose that's supposed to go from the thermostat housing to the heater core and then back to the thermostat housing simply is looped. Like the hose goes from one spot on the thermostat housing to another spot on the thermostat housing. Haha I hope you understand what I'm saying. But I'd assume this isn't the case for you

ike1

If that was the caswe I would think he wouldn't get heat on defrost.

ZINGGG

Haha oh man, something is wrong with my eyes tonight. Disregard my previous comment

Firestorm500

You've got a vacuum leak in one or more hoses under the hood.

Check the ones running along the inside of the right fender to the firewall first.

A-mac

I have checked the hoses under the hood and they all seem good but i was trying to follow them in to the cab but it looks like you have to pull the whole dash out to get to them. is there an easier way to get to the hoses behind the dash?

s14unimog

try the ol carb cleaner trick while the engine is running. Any leaks will affect idle.

On a side note, when relocating my vacuum ball I noted a thick sludge in my vacuum lines; you might have a blockage, rather than a leak. Try removing some of those "hard" lines (the plastic vacuum lines) and blow them out with compressed air.

Firestorm500

You may not be able to tell by just "looking" at them. You are going to have to take them apart section by section, block one end, and apply vacuum to the other end.

Heat and age get to the ones under the hood. Your problem is likely under the hood, or the vacuum ball behind the bumper, on the right side.

muffinman

Put your ear real close to the control switches on your hvac unit. Do you hear a slight whistling? Mine was acting like yours all the lines were good. I don't know what it is called but the plug all the vacum lines fit into on the back of the control was leaking. Got one at the j/t for a buck and that fixed it. Ok after further reveiw it was not making any noise. When I unplugged the vacum lines it did. When I covered all the ports it quit so that told me my lines were good. I have the piece here but can't get a pic of it right now. May not be your problem but it is free to check.

revsxj

check behind glove box there are color codes vacuum hoses that are for the switching between vents. also behind the controls itself

A-mac

ok i have been looking and my vacuum ball behind the bumper is not there lol. is this a big problem or can i bypass this some way?

revsxj

i would def get one alot of stuff is controlled by that

A-mac

well another question lol i am putting a custom bumper on the front. do i have to mount it in the bumper or can i mount it under the hood somewhere?

revsxj

what do you mean mount it in the bumper or under the hood?

A-mac

The vacuum ball does it have to be mounted in a certain spot to work right or can it be moved?