Chrysler Repair: Sebring 2001 LXI Coupe heater problem, car heater, heat problem

Question
107,000 km on car. Heater not producing much heat, intermittent sometimes with cool air blowing. Problem started on a very cold day, heater knob full heat. A plasticy smell occurred at full heat and heat cut out. When the knob was turned somewhat lower heat would come on again, full heat- smell returned. The smell was only the first day but the reduced heat problem has been since then. Had coolant checked, new thermostat, heater core flushed. First really cold day was this week and very little heat was produced the short time I drove. What else can I have checked?

Answer
Hi Norma,
Was the blower motor running at the time of the odor and was there any noticeable change in the sound of the motor or the quanity of air coming out of the vents. If so then I would suspect something to do with the blower or its plastic housing or duct. If not, then I would suspect something having to do with the 'blend air' door or the mechanism that moves it as that is what decides the mix of air between the heated and cooled/fresh air that produces the desired temp. If that door were in contact with the heater core it could have been overheated and deformed such that the heated air is totally bottled up inside the unit, and thus only cooled/fresh air is in the 'mix'.
Does the blower function on all speeds?
To examine the 'blend door you need to remove the lower edge of the instrument panel on the passenger side to give your access to the underside of the AC/heater unit. Then on the underside of the unit about in the midline you will find a wire connected to an electrically controlled blend door actuator. It is held in place by screws which when removed allow the actuator to drop down and off the bottom and reveal the connection between it and the shaft of the blend door. Note the position of the shaft in terms of its rotational movement so that it can be placed back in that position when you reattach the actuator. Then try and rotate the shaft of the blend door to see if it is free to move. Ideally it will do so or you can free it up so it will rotate. Then replace the actuator and see if you regain control of the temp without an smelling. Otherwise, it may be necessary to remove the unit and examing what has happened to melt plastic and loose control of the heat. That is a very major job because the entire instrument panel has to be removed to remove the AC/heater unit for disassembly
Roland
Roland