No matter which position the switch is in all the air comes out of the defrost. It is a 2003 Grand Cherokee Laredo. Its been happening for a few months and I'd loke to have it fixed before summer. I need help. When it started acting up you could cut it to the vents and cut off the ignition and back on. When I'd start the motor back up it would blow out of the vents. But now now matter what hot or cold or floor or dash, it always blows out of the defrost vents.

 

vaccum line!!!!

Check all of yoor vac line.

 

yup, the default position if there's no vacuum is defrost. there's a vacuum line coming out of the firewall on the passenger side where the evaporator lines come out. that vacuum line gets an engine vacuum, follow it and make sure its not broken or disconnected.

 

THats what my problem was. After posting the same question i went out and my father and i started looking and the vacuum line, big hose, from underneath the intake, bottom side of the throttlebody had popped off.

 

I found a vacuum line behind the headlight that was rotted and cracked. The a/c and heater work perfect now. But the cruise control still doesn't work. The CRUISE light on the dash comes on but it won't engage. I checked the wiring through the column and it ohmed out good. Could it be another vacuum line?

 

Could you please give details on where the vac line is located? I have the same problem on me 96 grand cherokee and I'm trying to find where is comes out from the firewall under the hood. You said that it was rotted and cracked behind the headlight. Was it the driver side or passenger? do you know where it comes out from the firewall and what does it look like?

Help is much appreciated.
Thanks
G

 

Hi, I am having the same problem with my a/c and heater only coming from the defroster. I see you fixed yours. I found that line by the headlight too, and it was cracked just fell apart when I pulled on it. i want to get new line, but now where does it plug back into??? PLZE HELP< IT'S HOT OUTSIDE
Stormy