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Chrysler Repair/'99 Chrysler 300m stuck on defrost


QUESTION: I had a conversation with you last Fall about the temperature sticking on defrost and you told me to check several fuses and a module..we did that with no luck.  A few weeks later I had to buy a new battery and the thing started working fine. It worked well all winter so I thought the new battery had something to do with it but after the hot weather arrived this Spring it started doing the same thing.  I have previously removed a fuse on the left side of the dash and the horn beeped and it reset the temp control to 75. After doing this for some time, it stopped responding to that action and nothing worked. I believe it has something to do with the inside temperature of the cabin because if I leave the car in the full sun it happens, in the shade it does not. So here is what I've been going through for the last 6 weeks. I took the car to a Chrysler Dealership and they told me the problem was the Controller Head..bam 700.00..2 days later it was doing the same thing so they told me sometimes they get bad Controller Heads and replaced it again BUT before they installed it they found that a previous owner had installed a Python security system and had removed it when they traded the car and had left a bunch of wires under the dash and that was the problem so they removed those wires at 80.00 per hour so that was another 700.00.  A few days later it was doing the same thing (--F, and would go to defrost) then they said there was a lose wire under the hood..a few days later it was doing the same thing. I have been there 6 times for this and each time I've asked them about the Module. They said there was nothing wrong with the Module. So I'm taking it back in the morning but I don't think they know what they are doing. Do you think it's the Module you spoke of last Fall?..I'm up to 1500.00 + with this repair and it is still not fixed..please help..Feed me some info to take to them tomorrow...thank you so much

ANSWER: Hi Janie,
Is this the '99 model year vehicle I discussed with Gery in June?
The ATC module has self-diagnostic capability you access by pushing simultaneously on three of the buttons on the module, while the engine is running. The buttons are the floor/mix/defrost.
The display should begin to blink, and when it does then release the buttons and see what numbers show up on the display. Let me know what happens.
The other thing to try is a "calibration" which I found in a later year manual. To do that, start the engine, turn on the control, run on full coldest setting for 2 minutes, then run of full hottest setting for 5 minutes.
If no codes nor calibration procedure works, then I would suspect that the "mode door actuator" is not functioning (though there should be a fault code number for that (24,33,39,or 40). That can be changed out pretty quickly if you have the manual. It is what moves the air distribution doors and it might be stuck in the defrost position.
Those are my ideas.
Please read the PS (below) and respond to it.

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QUESTION: Yes it is the 99 model you discussed with Gery...when I called the Chrysler place the man said it sounded like just what you said, the "mode door actuator" but has never mentioned that again..I think I will call them in the morning and cancel bringing the car back over there until we try what you suggested in the morning...thank you so much ..I'll get back with you tomorrow after we try this...I thanked you and said YES to your tomorrow..thanks

Thanks for the rating and nomination. I will only be available tomorrow morning, but will be again on Friday morning if we can't exchange q and a tomorrow.
One other idea is that perhaps the button for defrost is stuck in the closed position. So try simultaneously to push on just floor and the mix buttons (lower fourth, upper fifth) and hold to see whether that starts the code readout or not. If it did then that would suggest that were the case.  

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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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