Chrysler Repair: 99 LHS ATC, climate control unit, diagnostic mode

Question
My '99 LHS has some ATC heating problems.  The temperature seems to control when the car is parked at idle, When the car begins to move the air turns cold.  I have had the car on a scanner and watched as the blend door feedback drifted from +/- 3.5vdc to 0vdc, which I believe is full cooling.  I had  the vehicle in to a dealer and I believe they did some damage to the mode door, because now the air only diverts to the floor.  I also have a driver seat heater problem that seems to have happened at the same time, coincidence?  Neither lights Hi/Lo come on and no heat.  The dealer said the seat heater module was N/G then later said the heating elements needed to be replaced.  Would you have any idea on troubleshooting either or both of these problems?  Thanks, Jim

Answer
Hi Jim,
The first thing to do about the ATC is a readout of any stored fault codes in its memory:
TROUBLE CODES FROM THE ATC CONTROL
The trouble codes can be checked with the ATC control if a DRBIII® scan tool is not available. The control head can only be placed into the diagnostic mode while the engine is running and the vehicle is not moving. Set the control to a 75° F setting (so there is no confusion with the 23-51 Diagnostic Trouble Codes (DTC's)

To place the system into it's diagnostic mode, press and hold the Floor, Mix and Defrost buttons (at the same time) The ATC head display will begin to blink. Release the Floor, Mix and Defrost buttons. Once the control head enters the diagnostic mode, the display on the control head will continue to blink. This occurs until it completes its tests and climate control unit door/actuator calibrations. Then it will display any diagnostic trouble codes that are present in the BCM. If there are no diagnostic trouble codes, the system will return to its normal operation as indicated by the temperature symbol (a C or a F) Diagnostic trouble codes related to the ATC and climate control unit will appear on the display in numerical form. The diagnostic trouble codes are stored in the BCM and can range between 23 and 51. The ATC control can only show one diagnostic trouble code at a time. Under certain circumstances, more than one diagnostic trouble code could be in the memory. To scroll through any additional diagnostic trouble codes, press the Panel Mode button on the ATC control. It is important that no other knob or button is pushed until all codes are read. Pushing any button except Panel Mode or turning a knob will end the diagnostic test without showing the rest of the trouble codes. Let me know of the codes that come out and we'll go from there.

On the heated seat, check fuse 14 as well as circuit breaker no. 2 in the fuse box behind the left end cap of the dash. Other than that we will need to verify the wiring at the seat that comes from the fuse, and after that the switch and wires to the memory module that is under the seat, and to the cushion heaters.

Roland