Chrysler Repair: 1994 Chrysler LHS AC control head, 1994 chrysler lhs, chrysler lhs

Question
My 1994 LHS [244,000k Automatic Air] suddenly started blowing
hot air out of the defrost vents, and the display on the AC Heat
Fan etc. control head went black.  Only the AC control head
display went black, everything else works, the buttons were
completely unresponsive.  I tried resetting the control head with
various combinations of button pressing and disconnecting the
battery to no avail.  I left the vehicle for a couple of hours and
voila, the AC control display works and I have air conditioning
again.  Am I correct in assuming that it is the control head that
is malfunctioning and is it time to look for a new one?  Is there
any DIY repair possible on these units?  

Answer
Hi Garry,
Yes, you can at least get into the control unit and check things out. I have the wiring diagrams for '92 for the ATC unit and it shows there to be two separate subunits in the control unit, one for power supply and one for all the sensor and actuators. I suspect it is the power supply unit. However, if it happened once you may not want to start tearing into it that soon. Let me know if it happens again and I'll send you the wiring diagrams for it from a '92 Chrysler New Yorker which ought to be identical except for maybe the fuse assignment. You might want to check the fuse box in the cabin to see if you can find one that might be assigned to the heater/AC control panel and check that it is in good condition (not cracked fuse wire) and tight in the socket. The control unit removes easily, just take off the center console bezel and then the three retaining screws. I would suspect the power supply section and the best fix might be to get one from a wreck at a pull it yourself yard.
Roland
Roland