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Chrysler Repair/99 300M Climate Control Problem(s)


QUESTION: First of all, thanks for volunteering to answer questions here!

I'm trying to help a friend diagnose his climate control problems. The symptoms include:
1) Hitting the off button makes the unit shut down, then start back up on its own a few seconds later.
2) Temperature Display is simply two dashes (- -), and temperature up/down buttons have no effect.
3) Fan runs low speed when cold, then high speed when engine warms up.  Fan speed control has no effect. In effect, the unit seems intent on baking you out of the car!

ANSWER: Hi Gereon,
You are welcome!
It sounds like there may be a major failure in the control panel itself. But let us give a try for a self-diagnosis which the unit normally does do, and if it won't even do that then I have to believe the panel is our of order in a major way:
If it is the controller then your friend can run a self-diagnostic test to see what it thinks is wrong with itself. Turn the engine on, set the temp at 75>sno F (in this case you can't do that so just leave it as is), then simultaneously press the lower 4th button, the upper 5th button, the upper 6th button (floor, mix, defrost) and the control display should start to blink, then release the buttons and wait till the blinking stops to see of any 2-digit numbers show up on the display. If so, note it, and then press and release the upper 4th button to see any additional codes. Let me know the results.
Please 'rate' my answer (see below).

---------- FOLLOW-UP ----------

QUESTION: Thanks Roland,

Sorry for not following up sooner. I pressed the buttons as you described, and observed the following:

-After the blinking started, I released the buttons. The blinking continued for about 1/2 second, then the area that was blinking (temperature, manual/auto etc.) shut off and the snowflake (*) and defrost indicators came on. As I sat and watched the unit, I could hear whirring and clicking from within the dash, but nothing more changed onscreen. I waited about a minute, perhaps more, and still nothing changed. I was kind of in a hurry when I tested it, I didn't wait a terribly long time to see what would happen if I waited considerably longer.

Does this behavior change your opinion of the controller likely being the problem?

I see another control unit on ebay that is missing the leftmost button. I think I could get it pretty cheap for this reason. Do the buttons pop off and on fairly easily, so I could swap it with the current unit's buttons? I realize that it might actually be broken and not accept a button at all, but I don't mind gambling on that.

Hi Gereon,
If no two digit numbers appear after all the clicking is completed, then the unit should return a normal function, (i.e. a number followed by a C or an F, meaning a temperature setting). If it doesn't do that, and no twp digit fault numbers (without a C or an F) appear then I would guess that the control panel/display is faulty. You could try removing the button on his unit and in that way judge whether the eBay unit will be viable with the replacement button. Let me know how this works out, please.
Please 'rate' my answer (see below).

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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.

I answer questions seven days a week and respond to you in about 30 minutes. "Maxed Out" means I am answering another question, briefly unavailable, so try again later.

I have do-it-yourself experience (50+ years) and a library of 100 1982-2012 Chrysler factory shop manuals and 20 multi-manual Chrysler Corp. CD's.

I was voted "Top Expert" 2010-2015, here at AllExperts, and have answered 20,000+ questions.


Five decades as a 'do-it-yourselfer' on domestic and imported cars.

Yahoo Autos Group called The Chrysler Lebaron Club (co-moderator)

Advanced degrees in Physics/bruised knuckles

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"Top expert" of 2010, 2011, 2012, 2013, 2014 and 2015 here at Allexperts. Quickest "average response time" at Allexperts (currently no. 1).

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