Chrysler Repair: ATC A/C Problem, model units, labor time

Question
My A/C & heat- wont turn off.  In Manual I cannot adjust the fan speed.  The temp does change to the setting and when I push the off button it beeps, the display turns off, but just goes into automatic mode and keeps blowing at the temp it was set to.  Any Ideas?

1999 LHS LXI

Answer
Hi Penny,
I assume that you got some blinking, but then no number came up on the display, correct? If not, give it another try; be sure the engine is idling and the car is at rest.
Because it is an issue with not shutting off, I would next remove the control panel from the dash, remove its plugs, and then examine the off switch of the control panel to see if it is not changing the connections between the wires that are attached to it when the button is activated,as it should to accomplish the turn off function. If that were the case you might be able open the switch and repair it, or get another unit from a wreck and change out the switch/or substitute a used unit for yours. I believe you may find that all the dealer will offer at the parts counter is an entirely new control unit.
The other approach, involving dealer labor time, is to have them diagnose the system with greater capability using their diagnostic readout box (DRB III) and the body troubleshooting manual for that year and model. The box is much more sophicticated than the on-board code-read system so that might pinpoint what is wrong. But make sure they have the box, the manual to make use of the box, and a trained and competent tech, or it won't be worth it to have that done.
I unfortunately don't have the box or the manual myself so I can only tell you that they exist and may prove the most efficient way to correct this.
But the idea of getting a replacement control unit from a wreck is appealing to me too. You would want to be sure to know which year/model units are interchangeable with yours which the parts counter at the dealer may be able to help you to determine.
Roland





Hi Penny,
There is some on-board diagnostic capability built in to the ATC unit. It may give us some direction as to where to look to fix the problem. Here is how you access it:
Have the engine idling and set the temperature on the panel to 75 degrees, then push in and hold the three buttons: Floor, Defrost/floor, and Front Defrost buttons all at the same time until the display section blinks, then release the buttons.
The control display will continue to blink, and then show two-digit trouble code numbers if any are present, they range from # 23 to # 36.
Only one code can be displayed at a time, but pressing and releasing the Panel button will display the next code if present. If no more codes are present the display will return to normal.
Write back with the code #'s if any and I can decode them and then decide where to go next.
Roland