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Chrysler Repair/'99 300M: AC ATC control inoperative


hello..I have a 1999 300M. The AC is stuck on defrost..I tried holding the floor, mixed and defrost buttons down but did not get a code at all.  I turned the engine on, set the temp to 75 and did this..nothing happened.  None of the buttons are working except the temperature ..I can't turn it off or down...please help..thank you so much

Hi Gery,
The engine does have to be running, but the car itself at rest. Also, the three buttons have to be pressed simultaneously.
About the only other things to check would be the fuses:
Fuse 17 behind the end-cap of the dash powers the ATC unit, and that is probably OK because the readout is lit. The operation of the unit is however directed by the body control module and it has a number of fuses involved (but I can't tell which is needed for the ATC). So check out:
fuses 7, 14, 16, 18, 19 in the dash box, and fuse M in the power box in the engine compartment.
Let me know if you find any bad fuse. After that, the grounds and the digital bus wire from the atc to the body controller would be the next items to check.
Please 'rate/nominate' this answer/me (see the PS below).

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Roland Finston


Free fast answer to your repair question about a Chrysler/Dodge/Plymouth car, minivan, SUV, or truck. Problems with electronically controlled engines and transmissions as well as body wiring problems are my specialty. This free troubleshoot advice forum helps you diagnose faults, minimize repair costs or do-it-yourself.

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