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Chrysler Repair/'94 Chrysler LHS: theft alarm/ATC problems


QUESTION: couple of problems with my 1994 LHS.
First the heater/ac control randomly turns on and blows hot air through the front defrost vents. Don't know if there is a way to fix this or if i just have to purchase a new control. Also i have a problem when i lock my car. When i go to unlock it with the key the alarm sometimes goes off and is next to impossible to stop. Didn't know if there is a fix to this or just don't lock my car.


ANSWER: Hi Mike,
On the heater/ac control problem is this a conventional control unit or an automatic temperature control unit (with digital temp readout)? Let me know and we can proceed further.
Other than turning on by itself, does it function normally nonethe less?
One the theft alarm problem, it may be caused by a flakey wire from the driver door to the body computer due to wear and tear over the years. You can try to unlock the passenger side door to disarm it when this happens, as an alternative. The way to stop it from happening is to never 'arm' the system to begin with. That is done by never using the power door locks, the door key or the key fob (if you also have that) but instead use only the mechanical lock buttons on the interior of the doors to secure the doors. You can use the key to unlock it, but don't use that or any other electrical approach to locking it up. Then if you want you can troulble shoot that wire which is probably fatigued at the hinge and is in a harness of several wires at that point and is light green/orange in color.
There is no easy way to disable it permanently, but if you remember to never 'set' it, you won't have the issue.
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QUESTION: It's an automatic control unitl with the digital display.

thanks for the help on the door lock situation. So if i am understanding it correctly i should just push down each lock on the top of the door manually?


ANSWER: Hi Mike,
That is correct on the door lock closure procedure to by-pass the alarm arming.
On the ATC unit, do a self-diagnosis: With the engine running and the car at rest, turn on the unit and set it at 75. The simultaneously press the floor/mix/defrost buttons and hold them (those are the 1,2,4 buttons on the top row). Then the display will start blinking and when it does release all three buttons. Then wait and watch for any two digit numbers to appear in the display that range between 23 and 36. If one appears, note it, and then press the panel button to see if anyother numbers appear (that is the 1st button in the bottom row of buttons). Let me know what number(s) appear and we'll go from there.
Please 'rate' this answer also, and consider giving a 'yes' where you see the question about a 'nomination' for me to be 'voluteer of the month'.
Thank you,

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QUESTION: code 36 was what I got. Also missing what looks to be a relay on the back of the unit. Not sure what # I need to replace it?

Hi Mike,
That 36 code says that the digital communication of the system has somehow failed. It could be in the ATC control or in the twisted pair of wires between it and body control module with which it communicates. I am not familiar with the view of the rear side of the unit so am not certain what might be missing. Perhaps the parts counter at a dealership will show what it is in the parts manual. Check that out first, and then it may be that you either would get a dealer to readout the system using a Chrysler DRB-II type of anlytical box which might say specifically what is the cause/location of the communication failure, or look for a used ATC control box.
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Roland Finston


Get a 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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