Jeep Fan only runs on windshield-no matter what setting

I have a 2003 Jeep Grand Cherokee Laredo. The heating/air conditioning only runs on the “defrost” windshield setting no matter where I set the dial - feet, face, windshield, or any combo of the above. Am I doomed to forever have cold feet?

When the vacuum is lost to the vent system, it defaults to the defrost mode.

The vent system vaccum circuit needs to be inspected to determine if there’s a loss of vacuum to the system, or if the vacuum motor that switches between the different modes has failed.


So if it is a circuit, that is an easy fix, right? If it is a vacuum motor that is more costly, eh?

The vent system vacuum reservior is located behind the right side of the front bumper. Check the vacuum hoses here first. If these appear fine, follow the hoses up to the engine compartment and check for leaks for the hose that goes to the engine, and the hose that goes through the firewall to the passenger cabin. If these appear to be fine, then look under the dash to see if any hoses are leaking in this area. If none are found, then check the vent control module where the controls are for leaks. If none are found, then remove the glove box to gain access to the vent control vacuum motor to see if it’s leaking.