air vents change on there own

90jeepXJ

New Member
Joined
Jul 3, 2005
Location
winston-salem
I turn on the a/c or just the vent it will some times go between defrost and the vents. it got stuck on the defrost vents along time ago and a vac line came off but i cant remember where it is.
 
Is this a question or a statement ?
 
It may have a check valve that has gone bad on the vacuum feed line. When sitting at idle the dash vents may work and when you accelerate the vacuum goes away causing the defrost vents to open.
 
Thanks to the ever increasing government control in our lives:flipoff2:, all vehicles must default to defrost for safety. Thats also why we don't have chrome/shiny paint in the interior. As to why yours is going to defrost, I don't know, sorry.
 
My wrangler was doing the same thing. Defaulting to Defrost and it was the vacum lines underneath the drivers side dash. Just to the right of the steering column. Not sure where your vacum lines are running but that would be the first thing I would check.
 
I am not sure how simular the YJ is to my J10 but the was a mechanical spring loaded vacuum valve behide my dash that got stuck in the def Posistion. Had to take it out and lube it up to get it move freely.
 
The 90 xj has lots of vacume lines for all sorts of things. My guess is to start with the vacume canister and the lines on the different actuators under the dash.
 
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