Vacumn leaks..........

[techno1154]

.......real bad behind the dash but only when the interior heater/air conn switch is moved to the on position. The air coming out of the vents had always changed to the defroster when climing long hills especially after I changed to 30" tires but now the Xj only has to see a slight upward grade and all the air blows from the defroster vents.
One test I did that confirms the locality of the leak was to park the XJ over night with the heater switch off then check for vacumn in the morning. There seem to be no loss of vacumn next morning. However if the switch is turned on with the engine off, the vacumn leak out in less than (well close to) a minute. I took the dash apart to look at things behind there but all I see is a bunch of spaghetti hoses dissapearing in a harness wrap.
What is the easiest way to locate the culprit end convinse him to act the way he is supposed to?

 

[1985xjlaredo]

There is a "vaccum harness" that plugs into the back of the ac/heater control. The system is set by default to blow out of the defroster incase something like this ever happens. I know that they changed from year to year but I had my 88 apart and got a used controler off of ebay. The plug is tight as hell to get off and then there is absolutly no slack in it when you pull the control out of the dash. I had to get the plug off and I just used some mineral sprits to get the vaccum lines out of the plug. Just remember where they go!!!! I dont think that anyone has a diagram for them. but mre than likley this is what has gone wrong with yours. My 88 is a rectangle block and my 85 is a round disk. hope this helps.

 

[GrimmJeeper]

i have a 95 should be the same as yours... make sure the plug going into the back of the ac control unit is pushed all the way in, its uncommon for those hoses to break or crack... i was hearing a hissing noise in there after i put my radio in and checked the vaccuum by blowing cig smoke at the plug back there with the enginge running, it was sucking in around the side of the plug.. i pushed it in harder and the noise went away

hope this helps
-mike

 

[jesterbomb]

Sweet! See, just by coming here and asking, you have just found another excuse for smoking.

"Uh, I just keep these around to fix my heater controls..."

I actually sprayed coffee at my screen. Grimmjeeper, that is awesome. That would work a lot better than some of the things I've heard. Little styrofaom balls, flour, paint... Honestly, there was actually a guy at work who tried paint. In his girlfriends car. He came in the next morning single and riding a bycicle.