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You are here: Experts > Home/Garden > Auto Repair > Chrysler Repair > heating system
Expert: Roland Finston - 11/10/2009
Question
i have a 97 chrysler concorde LTI and when i shut the heat and fan off the front defrosters on the dash keep going...i get heat through all the vents and floor and everything works right but when i shut everything down the front defrosters keep going on high...when i push the off button that does not help....if i have the heat on and switch to vent, it will transfer to any other vents but goes right back to defrosters when off...someone said it would be a body control module...is there any diagnostic test? and where can i get one that doesn't cost a fortune?
Answer
Hi Ann,
There are 2 types of heater/AC controls: a conventional unit and a digital temp readout unit. Both of them have self-diagnostic capability. Here is the procedure for conventional unit, please let me know if you have the digital readout unit and I will give you the procedure for that one.
The LH models (LHS, Concorde, New Yorker, Intrepid, Vision) do have self-diagnostic capability with the standard type heater controls. There is a rear window defogger that is initiated by a push button with an LED light. That light is the readout, by its blinking. To begin the diagnostic mode, run the vehicle at idle with the controls set as follows: the blower speed knob should be on any position other than OFF, the temperature knob should be set in full COOL, and the mode knob should be set on Defrost mode.
To enter the diagnostic mode, press the defogger switch in for five seconds, until it begins to blink, then release it. It will continue to blink for about 30 seconds while it calibrates. If it goes out, the calibration is OK and you can skip 3 paragraphs to "Position...mix mode" below.
If the light stayed on, switch the mode knob to the MIX (defroster-floor) position. If the light stays on there is a problem with the control head unit.
Switch the mode knob to the FLOOR position, if the light stays on, it indicates a problem in the blend door or the blend door actuator wiring.
Move the knob to the Bi-level (panel-floor) position where a continuous light indicates a problem with mode actuator or circuit.
Position the knob in the MIX mode. The LED light should now flash twice then pause, and continue a two-flash sequence, indicating that the MIX mode is OK.
In the FLOOR mode the light should flash three times, meaning that the FLOOR mode is OK.
In the Bi-Level Mode, a four-flash sequence indicates that mode is OK.
In the PANEL mode the light should flash 5 times to indicate no problems there, and in the recirc-panel mode 6 times and seven times in the recirc Bi-level mode.
The temperature control can be checked by switching the mode knob to Defrost and rotating the temperture knob. If the temperature contol is OK, the light will flash faster the more you turn the temperature knob up, until the light goes out at the hottest setting.
Switch the knob between Panel and Recirc-Panel and watch the recirc door (unit under the dash). Proper operation means that circuit and components are OK.
To get out of the self-diagnostic mode, turn off the blower or push the air conditioning button once.
If this doesn't seem to apply to your control head or you get no response from an LED light for the rear defroster, then the Sebring may not have this capability. Please let me know your results if any.
When you say the unit switches to the front defrosters, does that mean warm air or cold air is coming out? And if the unit is 'off' and you start the car then the blower comes right on?
When it is showing this malfunction do you hear the AC compressor cycling on and off? Please tell me again which type of unit you have: conventional or digital
Roland
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