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Unread 10-22-2013, 10:44 AM   #1
johngreen1234
Registered User
2010 WK 
 
Join Date: Nov 2012
Location: beverly hills, ca
Posts: 301
Ghost in the A/C

When I bought my 2010 with the MANUAL hvac last year, there was a problem with the A/C that went away almost immediately, too quick for a dealer to diagnose. Yesterday it came back (briefly) and then went away again. Two episodes in one year.

What has happened is that the A/C will blow hot air on any setting:

AC button on, temp on coldest--hot air.
AC button off, temp on coldest--hot air.
AC button on, temp on warmest--hot air.
AC button off, temp on warmest--hot air.

AC on or off doesn't seem to affect the AC compressor, and the manual temp setting hot or cold doesn't seem to affect the heat setting. It is full heat coming through the vents, and I tried switching vent settings without any effect.

I was driving down the highway when it started working again. I didn't hear anything "click" like the blend door finally moving and besides, even with a bad blend door wouldn't you still get the AC compressor to switch on when manually activated? Mine didn't.

I was told at one time that it could be the HVAC head unit--I forget what they're properly called. What says the group? Blend door, or head unit, or something else?

Thanks!

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Unread 10-22-2013, 11:39 AM   #2
yzjwk
Registered User
2005 WK 
 
Join Date: Apr 2011
Location: Lac du Bonnet, manitoba, Can
Posts: 1,101
The manual temperature controls have a diagnostic built in with a reset calibration you can try , EBL = defrost switch
to get the DTC's
NOTE: The A/C status indicator displays active DTCs when the EBL status indictor is not illuminated and
stored DTCs when the EBL status indicator is illuminated.
² Perform the following to read DTCs from the MTC: 1. Turn the blower control on. 2. Press the A/C
mode switch down, turn the blower control to off, wait 5 seconds and then release the A/C mode
switch. 3. Read the DTCs from the flashing A/C status indicator.

to erase DTC's:
Perform this step only if diagnosing faults related to the HVAC system.
² The Manual Temperature Control (MTC) is not on the Bus and not addressable with a scan tool.
Perform the following to clear DTCs from the MTC: 1. Turn the blower control on. 2. Press the A/C
mode switch down, turn the blower control to off, wait 5 seconds and then release the A/C mode
switch. 3. When the A/C status indicator begins flashing DTCs, set the Mode switch to the floor position,
simultaneously press the A/C mode switch and the EBL mode switch down for 5 seconds and
then release the mode switches

to re calibrate
For vehicles equipped with MTC, if repairs were made to any of the HVAC doors, linkage, door actuators,
or door actuator circuits, run the door calibration function by performing the following: 1. Turn the
ignition on. 2. Turn the blower control to off. 3. Press the EBL mode switch down, turn the blower
control on, wait 5 seconds and then release the mode switch. Wait approximately 90 seconds for the
calibration process to run to completion before proceeding.
__________________
5 and counting :05 WK 5.7 HEMI
90 YJ Islander 4.2L
94 ZJ Ltd 5.2 ,00 WJ 4.0
2010 MK Patriot
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