Control Assembly: Testing and Inspection

Satisfactory heater and air conditioner performance depends upon proper operation and adjustment of all operating controls and refrigeration system components. These inspections, tests, and adjustments should be used to locate the cause of a malfunction.

Operation must be tested as described in the following sequence:
1. Inspect and adjust the serpentine drive belt.
2. Start the engine and set the engine speed to 1300 rpm.
3. Move the temperature control knob to the full counterclockwise (Cool) position and place the mode control knob in the Bi-Level position. The outside (recirculation) air door should be open to outside air. If not OK, see Vacuum System.
4. With the temperature control knob in the full counterclockwise (Cool) position, the air being discharged from the outlets should be near ambient temperature. As the temperature control knob is rotated clockwise beyond the third detent, a gradual warming of the air being discharged should be noticed. If OK, go to Step 6. If not OK, go to Step 5.
5. Roll down the glove box from the instrument panel. Look through the instrument panel glove box opening to locate the blend-air door motor on the top of the distribution duct. While rotating the temperature control knob through its travel, check that the blend-air door motor lever is moving and that the blend-air door link is connected to the lever. If OK, see Heater Performance. If not OK, see Blend-Air Door Control.
6. Open the vehicle windows. Test the blower motor operation in all speeds. If not OK, see the tests for the individual blower motor components. Leave the blower motor switch in the highest speed position.
7. On vehicles with air conditioning, the compressor should be running and the air conditioning system in operation. If not OK, see A/C Performance.

Mode Control Chart:

8. Check the heater-only or heater-A/C mode control switch operation. The systems should respond as shown in the Mode Control chart. Reduce the engine speed to normal idle. The vacuum will be high at low idle and the actuators should respond quickly. If not OK, see Vacuum System - Heater-A/C Controls.
9. If the vacuum tests, and the electrical component and circuit tests reveal no problems, disassemble the heater-A/C housing, the recirculation housing and the distribution duct to inspect for mechanical misalignment or binding of the mode doors.