Air Door: Testing and Inspection

BLEND-AIR DOOR CONTROL TEST

The blend-air door in the heater-A/C housing is controlled by a combination of mechanical linkage and electronic controls. The mechanical linkage is connected to the blend-air door pivot shaft lever in the engine compartment on one end, and to the blend-air door servo motor lever in the passenger compartment on the other end. The blend-air door motor is controlled by the temperature control knot through a potentiometer that is integral to the heater-only or heater-A/C control assembly.

WARNING: ON VEHICLES EQUIPPED WITH AIRBAG, REFER TO AIRBAGS AND SEAT BELTS/AIRBAGS BEFORE ATTEMPTING ANY STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENT DIAGNOSIS OR SERVICE. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY.

1. Check the fuse in the junction block. If OK, go to Step 2. If not OK, repair the shorted circuit or component as required and replace the faulty fuse.
2. Turn the ignition switch to the ON position. Check for battery voltage at the fuse in the junction block. If OK, go to Step 3. If not OK, repair the open circuit to the ignition switch as required.
3. Turn the ignition switch to the OFF position. Disconnect and isolate the battery negative cable. Roll down the glove box from the instrument panel.
4. Connect the battery negative cable. Turn the ignition switch to the ON position. Look through the instrument panel glove box opening to locate the blend-air door motor on the top of the distribution duct. Check that the blend-air door link is connected to the blend-air door motor lever. If OK, go to Step 5. If not OK, see Blend-Air Door Motor.
5. While observing the blend-air door motor, slowly rotate the temperature control knob from stop to stop. The motor lever movement should correspond to the movements of the temperature control knob. If OK, check the blend-air door in the heater-A/C housing for damage. If not OK, go to Step 6.
6. Turn the ignition switch to the OFF position. Disconnect and isolate the battery negative cable. Unplug the wire harness connector from the blend- air door motor. Check for continuity between the blend air door driver circuit cavity of the blend-air door motor wire harness connector and a good ground. There should be continuity. If OK, go to Step 7. If not OK, repair the open circuit to ground as required.
7. Connect the battery negative cable. Turn the ignition switch to the ON position. Check for battery voltage at the ignition feed circuit cavity of the blend-air door motor wire harness connector. If OK, go to Step 8. If not OK, repair the open circuit to the junction block fuse as required.
8. Turn the ignition switch to the OFF position. Disconnect and isolate the battery negative cable. Check the resistance between the blend air door driver circuit cavity and the ignition feed circuit cavity of the blend-air door motor wire harness connector. The resistance should be from 8.5 to 11.5 K Ohms. If OK, go to Step 9. If not OK, go to Step 12.
9. Move the temperature control knob to the full counterclockwise (Cool) position. Measure the resistance between the ignition feed circuit cavity and the blend door feedback signal circuit cavity of the blend-air door motor wire harness connector. The resistance should not be more than 100 ohms. If OK, go to Step 10. If not OK, go to Step 12.
10. Move the temperature control knob to the full clockwise (Warm) position. Measure the resistance between the ignition feed circuit cavity and the blend door feedback signal circuit cavity of the blend-air door motor wire harness connector. The resistance should be less than 10 ohms. If OK, go to Step 11. If not OK, go to Step 12.
11. Measure the resistance between the ignition feed circuit cavity and the blend door feedback signal circuit cavity of the blend-air door motor wire harness connector while slowly rotating the temperature control knob from stop to stop. There should be no spikes greater than 11.5 K Ohms. If OK, replace the faulty blend-air door motor. If not OK, replace the faulty heater-only or heater-A/C control unit.
12. Remove the heater-only or heater-A/C control from the instrument panel. Check for continuity between the blend air door driver circuit cavity of the blend-air controller wire harness connector and a good ground. There should be continuity. If OK, go to Step 13. If not OK, repair the open circuit to ground as required.
13. Connect the battery negative cable. Turn the ignition switch to the ON position. Check for battery voltage at the ignition feed circuit cavity of the blend-air controller wire harness connector. If OK, go to Step 14. If not OK, repair the open circuit to the junction block fuse as required.
14. Turn the ignition switch to the OFF position. Disconnect and isolate the battery negative cable. Check the resistance between the blend air door driver circuit terminal and the ignition feed circuit terminal in the blend-air controller receptacle on the back of the heater-A/C control. The resistance should be from 8.5 to 11.5 K Ohms. If OK, go to Step 15. If not OK, replace the faulty heater-A/C control unit.
15. Move the temperature control knob to the full counterclockwise (Cool) position. Measure the resistance between the ignition feed circuit terminal and the blend door feedback signal circuit terminal in the blend-air controller receptacle on the back of the heater-A/C control. The resistance should not be more than 100 ohms. If OK, go to Step 16. If not OK, replace the faulty heater-A/C control unit.
16. Move the temperature control knob to the full clockwise (Warm) position. Measure the resistance between the ignition feed circuit terminal and the blend door feedback signal circuit terminal in the blend-air controller receptacle on the back of the heater-A/C control. The resistance should be less than 10 ohms. If OK, repair the blend door feedback signal circuit to the blend-air door motor as required. If not OK, replace the faulty heater-A/C control unit.