99 park ave climate control drift

[msi84]

The cc initially operates correctly with only the standard clicking from the driver blend gate. Temp @72 deg (outside temp 60)and heat flows. After driving for an hour or more, air gets colder and colder. The only way to get heat back is to advance temp setting to 90deg. Also, I noticed that when this happens, I can't get much heat from vents in manual, and in MID. Air flow does seam to flow out the defrost though regardless of position setting. Very little from floor unless set to 90.

[bigsky]

Originally Posted by msi84

The cc initially operates correctly with only the standard clicking from the driver blend gate. Temp @72 deg (outside temp 60)and heat flows. After driving for an hour or more, air gets colder and colder. The only way to get heat back is to advance temp setting to 90deg. Also, I noticed that when this happens, I can't get much heat from vents in manual, and in MID. Air flow does seam to flow out the defrost though regardless of position setting. Very little from floor unless set to 90.

Maybe the inside temperature sensor is bad. It is behind the dash piece below the shift lever.

There might be another inside temp. sensor. EDIT - There is a left and right temp. sensor on each bottom hush panel. There also is the "sun" load sensors which also affect temperature. These are the two domes on the top of the dash, left and right side. The flat sensor in the middle is the light sensor for the auto headlights.

Another problem could be the thermostat. If you have the gauge cluster, is your coolant heating up to 195 degrees or more? Maybe radiator needs flushing.

[msi84]

The T-Stat is fine. Digital temp indicated normal range. The sensors could cause this as it seams that the system thinks there is a need for defrost and that is what happens. The air flow seams to want to come out the defrost vent despite my setting it to Floor. It only blows out the floor if I kick up the temp to 90deg. Fan speed works but not out the floor. Isn't there some condition that tells it to defrost or dehumidify? I seam to remember something about this. Anyway, The system works fine for about an hour and then acts up when I am least able to fiddle with it.

[bigsky]

Originally Posted by msi84

The T-Stat is fine. Digital temp indicated normal range. The sensors could cause this as it seams that the system thinks there is a need for defrost and that is what happens. The air flow seams to want to come out the defrost vent despite my setting it to Floor. It only blows out the floor if I kick up the temp to 90deg. Fan speed works but not out the floor. Isn't there some condition that tells it to defrost or dehumidify? I seam to remember something about this. Anyway, The system works fine for about an hour and then acts up when I am least able to fiddle with it.

Check for DTC using scan tool or on-board:

Hold OFF, AUTO, and RECIRC for 1 second.

The DTC's will display for 2 seconds each then return to normal. I have the service manual with DTC codes.


Could be the MODE ACTUATOR is failing. This adjusts the air flow to top, middle, and bottom.
DTC B1344 Mode door movement fault.

Maybe the Heater/AC Programmer is going, or could try the disconnect negative battery cable for a few and then reconnect to reset system. Before doing this and turning car off make sure the heat/AC is off. Some have reported their system went a little haywire when the system was left on, car was shut off, and the battery was then disconnected.