QuestionHi Roland! My Mother has the 1994 Chrysler Concorde with
the fully automatic climate control, and it has recently
become stuck on high heat with no display on the head unit.
It cannot be turned off with the controls, cannot be
adjusted, and is baking my dear sweet Mother alive!
Before this -- for at least the past year or so -- the
digital display would intermittently go out, and then the
fan speed would go to high and HOT air would be directed
only to the defrost vents. But the display would usually
come right back on, after which it would be set to non-auto
and some lower temperature like 68 or 70 (can't recall
exactly). We would then have to reselect the desired
temperature (72) and press the Auto button again, and it
would again begin maintaining the original temperature, fan
speed, and vent direction as though nothing had happened.
Am I looking at a head unit replacement? I am decently
handy with a soldering iron, so if there's something inside
that typically fails due to weak soldering, maybe I can try
repairing that myself?
I was originally thinking the blower speed resistor was the
culprit, but I figured I'd ask you first before even buying
it. Why? Because the only one I can find at the parts
store has only a couple coiled wires in it. I'm fairly
certain this ATC system uses far more than 3 or 4 fan
speeds, because it gradually builds from off to high speed
when it works correctly. Then again, I may be confusing it
with a rental car I was just in...
At any rate, I really look forward to your answer, Roland.
Your expertise concerning Chrysler vehicles has been such a
HUGE help to our Chrysler-loving family for years. Thank
you! And Happy New Year!
AnswerHi Tre,
Thanks for the kind remarks and New Year greeting.
You are correct about the blower motor power unit, the ATC uses a solid state module to produce the multiple fan speeds. The resistor "block" is for the conventional 4-speed control panels. I would not buy the module until we get the control panel working, however.
I would be inclined to remove the ATC control and look inside of it to see if you can identify an elecrolytic capacitor that may have failed (usually leaves a trace of dried up dielectric) probably fairly near the power input on the circuit board. Once you are at the rear plugs check to be sure that you have 12v coming from fuse #6 on the white wire of pin 5 when the ignition is 'on'. Also, be careful of pin 1 of the 2-pin plug because it is a direct feed from the battery for the rear window defogger current and is hot all the time. I believe that if you can revive the controller all the problems may resolve, or at least we can go on from there.
The unit does rely on the digital data bus to communicate its commends to the actuators on the air distribution system, but that issue is probably secondary to the complete blackout of the display and loss of control.
In the meantime, you can gain manual control of the temperature output by removing the blend door actuator and moving the door to a more middle position (it may move on its own once freed, however, so check that out). The actuator is on the bottom of the unit at the center tunnel. You remove the under panel silencer/ducts on both sidesto gain access. Then locate the acturator which has two screws holding in place from the right, and one screw on the left side of it. Pull straight down. Notice the position of the interface key between the unit and door fitting for subsequesnt rematching later. Then move the door by turning the connector interface attached to the bottom of the door.
Roland
