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98 or 99 A/C, blend door & control issues

1K views 3 replies 3 participants last post by  rxmotoman 
#1 ·
I have a salvage jeep with the Rotary (3 knob) A/C controls. The A/C has never worked for more than a few minutes and numerous people have looked at it. I can force the compressor on by jumping it straight to the battery but no luck with switches. Only will blow hot.
I get different reports from different people, did all 98s have slide controls (+ slide blend door control) or did they mix the year? I need to match the wiring with 98 or 99 or 00.

If anyone can shoot me pictures or wiring colors would be great. The local salvage yard said I cannot mate the rotary (99+) controls to 98 A/C unit under the hood, is this true?

I have checked the HI/Low switches and the compressor, all are ok. I have replaced the Switch Control at least twice b/c it's hot enough to cook on it most of the time and the switches and main wires get hot.
 
#2 · (Edited)
I could be mistaken, but most of the TJ's have a vacuum controlled blend door arangement to control the temperature. Without any vacuum to the door actuator, it will rest at full heat, as a safety measure to prevent the windows from freezing over in winter. Usually, it will also default the Mode door into Defrost only, too. This may account for the A/C working for a few minutes, until the engine gets warm and the heater core's heat overpowers the A/C evaporator's cooled air.

Verify that there is vacuum to the dash controller. If no, repair the lack of vacuum issue. There usually is a vacuum reservoir under the hood. I don't recall where it is. (Might be under the battery tray?) There are plastic hoses between the reservoir and the dash controller. Near the battery, they often get eaten up by acid leaks from the battery. Carefull listening may pinpoint a vacuum leak in the harness. A wreck may have cracked or disconnected the vacuum reservoir. Body shops often leave it off or disconnected.

If you have vacuum check the actuator at the blend door. The blend door actuator is on the left (Driver's) side of the HVAC unit, if I remember right. Sometimes the lever into the door will break off, and the door will become inop. The lever used to be available separately, and the broken piece of the lever could be extracted with a sharp 2" long drywall screw insered into the broken off lever shaft through the side of the HVAC unit. The new lever is then snapped into place and the actuateor reconnected to it.

Hope this helps!
 
#4 ·
Thanks Marty SoCal. Very impressive write up! I'll check the vacuum again. I can hear the vacuum release when i shut off the jeep, depending on the day. The actuator has never worked, i used to be able to turn the lever by hand but I lost the lever a couple months ago. I called the Salvage yard and he told me he would sell the actuator but not the lever unless he sold the whole heater box and that mine was a 99 not a 98 if it had rotary controls. If anyone knows where to get the actuator and lever, let me know.
 
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