QuestionThanks for getting back to me so fast. So I checked the on-board diagnostics. The system sounded like it was going through a self check, and no codes appeared, after the lights quit flashing the standard display appeared. What should I check next, or is this something better left to a dealer with specialized diagnostic equipment? Thanks again for your help.
-------------------------------------------
The text above is a follow-up to ...
-----Question-----
The auto temp control seems to work fine when the car is warming up, but after 15-20 minutes of driving, blows outside temperature air. The atc control panel has been replaced, fluid level is correct and has been bled. All indications on the atc panel seem correct. The problem exists in both manual and automatic mode. Car now has about 135K. The same problem occurred at 29K and the atc panel was replaced at that time. This time, it did not fix the problem. Any help would be appreciated. Thanks,
-----Answer-----
Hi Ed,
The control panel has a self-diagnostic capability that might point us toward a solution. I suspect that one of the doors in the underdash HVAC system proper is not responding to commands from the control panel, so let's try for a clue. Here is how I responded a few weeks ago to a similar situation. However, the owner hadn't replaced the control unit yet:
"The unit does have a self-diagnostic capability. The engine has to be running and the car not in motion to do the test. Simultaneously press the floor, defrost/floor, and defrost only buttons, (the 1st,2nd and 4th on the top row) and see if the display unit begins to blink. Release the buttons when it has started to do that and then after it blinks for a while longer watch for two digit numbers to appear on the readout. Those are the fault codes. If the first number appears and stays in place, push on the first button in the bottom row (panel) to continue the readout. At the end of the readout the unit will return to normal settings.
Then write back with the number(s) and also tell me more about exactly what is wrong with the function of the unit.*
I would do a thorough readout before buying a new control unit. It may be a part in the air distribution system itself rather than the computer that is the problem. And you also might find a working used unit at a wrecking yard.
Roland
*The code numbers range from 23-36. You can also get a decoder list at www.allpar.com/fix/codes_climate.html "
AnswerHi Ed,
You are correct that a more complete analysis of the ATC can be done via the diagnostic readout box (DRB III). So because there are no codes that would be the next step.
One last thing you might want to check is whether the small fan (aspirator) in the cabin which takes in air to flow it across a temperture sensor is working or not. It is said to be located on the dash behind the grille that says "Chrysler 300M". So turn on the ATC with the engine running, etc. and as a test of the aspirator take a small piece of tissure paper and hold it by the edge at the grille and observe to see whether the paper is pulled toward the grille by the incoming air. It should be, and then continue to observe this to see whether, after the elapsed time when unit ceases to heat, that the tissue still is sucked against the grille. If not, then the aspirator motor is giving up after a few minutes, and needs to be replaced.
Good luck on your efforts to get a steady source of heat.
Roland
