Single Zone HVAC Problems
I have been fighting with this annoying behavior with my 2004 Columbia Edition (same controls at a Laredo) with the 4.7 HO for quite some time. The air flow will shift from the setting selected on the control knob back to the default "defrost" setting. This happens any time the engine goes under load. I know this is vacuum-related and have taken the following steps to fix the problem:
- Checked and replaced the check valve between the throttle body and the HVAC controls and cruise control/vacuum canister (located behind the bumper)
- Replaced bad line from inner fender/frame rail to cruise control
- Dealer replaced hard line that runs from throttle body to the HVAC control and inner fender/frame.
I have also noticed that when the vehicle goes under load I can hear a vacuum noise in the the passenger compartment. This leads me to believe it could be a vacuum fitting under the dash. I am looking for a vacuum diagram but have not been able to find one for under the hood and in the dash.
Can anyone help with this? Any suggestions?
2004 Columbia Edition WJ 4.7 HO
RB4/Moog HD Steering Stabilizer/PML trans pan 10304/ Autometer trans temp and oil pressure gauge/UpCountry springs & OME 10MM Spacers/Bilstein shocks/Rubicon Moabs/255/65r17 Cooper Discoverer AT3/Factory chrome tow hooks/Mopar hitch & a loose nut behind the wheel