System Check - RPO C68

Figure 2 System Response/Operation:

FUNCTIONAL TEST
The following is a list of quick checks used to determine if the system is functioning properly. Before initiating the quick check procedures, cycle the ignition switch "ON," "OFF" and then "ON" again. The control panel temperature and mode LEDs should light and repeat at the same positions as the ignition is cycled. With the ignition on without interruption for a minimum of three minutes to allow for the blower delay to time out, test the "HEAT" and "BI-LEVEL" functions. A check of the following mode sequences indicates if any mode selections are not functioning properly. The compressor will not operate at ambient temperatures below 10°C (5O°F).

^ Set temperature to "65" and select "AUTO" setting. Cold air should flow out the instrument panel outlets, blower should run at high speed, and noise level should change when in recirculation. While in the "65" "AUTO" setting, hold a small piece of paper against the inside air temperature sensor holes. If the sensor hose is aspirating correctly, the paper will remain against the sensor holes. If not, it will fall to the floor.

^ Set temperature to "85" and select "AUTO" mode setting. Warm air should flow from the heater outlet and the blower should run at high speed.

^ Set temperature to "85" and select "DEF" setting. Warm air should flow from the defroster outlets, and blower should run at high speed.

^ Set temperature to "75" and select "BI-LEVEL" setting. Air should flow from the instrument panel and heater outlets and blower speed should slow down. If blower speed remains at high speed, there may be a sensor problem.

NOTE The vehicle must be in a garage and under room temperature conditions.


Blower Delay
The blower delay timer is active only when the system senses it should be putting out heat in "ECON," "HEAT," "AUTO," or "BI-LEVEL" modes. The blower delay timer keeps the blower off for 3 minutes to allow the engine coolant to warm up. In cases of very cold ambients, delay can last up to 4 minutes. To check for correct operation of the blower delay timer:

^ Select "65" and "HI". No delay in system operation should occur.

^ Select a high guide temperature setting and either "ECON," "HEAT," "AUTO" or "BI-LEVEL" modes. The blower delay timer should engage, keeping the blower off for 3 minutes (no longer than 4 minutes), until engine coolant has warmed up. Then, the blower fan should be energized.

In the "HI" or "DEF" modes or when cooling is required in "AUTO," the blower delay timer will not function, nor should the timer function once the engine is warmed up. After the blower has come on, it will not be delayed again even if ignition has been switched "OFF" until a capacitor in the timer has discharged. It takes approximately one hour with the ignition "OFF" to discharge the capacitor.

The control assembly must have a constant battery positive (+) feed to maintain memory function.

If the system does not function as described in these checks, refer to Testing and Inspection under the appropriate component, after referring to the diagnostic procedures in the Variable Displacement Orifice Tube Diagnostic Charts. [1][2]Symptom Related Diagnostic Procedures