Chrysler Repair: 1994 Concorde w/ No Heat, automatic temperature control, communication issue

Question
I have a 1994 Concorde with no heat.  The blower is only blowing cold air through the defrost vents and the level of fluid is fine in the radiator.  I have done the diagnostic test on the Automatic Temperature Control and received the trouble codes of 25 and 36.  I do not understand what code 36 means and how to repair the heater.  

Answer
Hi Nikki,
The 25 code indicates a problem with the in-car aspirator (small fan and temperature-sensing thermistor). That is located behind the nameplate just above the glove box. You can turn on the ignition switch but then turn off the ATC control panel via the pushbutton. Then hold a small piece of tissue paper in front of nameplate opening to see if it is drawn to and sticks to the nameplate which would show that the aspirator fan is working. It is possible that the thermistor is no longer working if the fan is working.
Other than that, the 36 code says there is a communication issue with the control panel itself. Diagnosing that requires a Diagnostic Readout Box (DRB II) at a dealer and assuming they have a competent tech or a manual available. Maybe the easiest and least expensive thing might be to find a used unit in a junk yard. Call around/visit pull-it yourself yards to find a similar car with the same ATC control unit. It is pretty easy to remove and replace:
Turn off the ignition
Remove the bezel that surrounds the center console. You may have to remove the ash receiver. Then the bezel appears to pull straight back for removal.
Then remove the screw on either side of the control panel and pull it back. Then disconnect the plugs on the back of the unit.
The reason for the cold air only is probably a fault in the control unit communication or the blend air door that it controls which proportions the air flow between the heater core and the incoming air as needed to produce the desired temperature. There is a code for the blend air door (23) so presumably it is not the actuator for the door but rather either the in-car sensor is not telling the ATC what the temp is inside the car or the ATC is not communicating with the sensor or the blend air door properly. So maybe to avoid labor costs, getting a used ATC control unit is the most economical fix unless the aspirator proves to not be sucking air as measured by the tissue paper test. The fan is supposed to run when the ignition is "on" even though you have the ATC set to off.
Roland