Insufficient Defrosting; Noise From Blower Motor - Chevrolet Trailblazer Service Manual

Insufficient Defrosting

CAUTION
Check all fluid levels and adjust as needed, before operating vehicle for extended periods
at idle.
1. Start the engine, select the DEFROST mode, and select the maximum blower
speed. Does sufficient air flow from the defroster outlets? If yes, go to the next
step. If there is insufficient airflow, go to step 9.
2. Measure the engine operating temperature. Does the engine reach normal
operating temperature (approx. 200° F)? If yes, go to the next step. If the engine
does not reach normal operating temperature, go to step 7.
3. Select the minimum blower speed. Select the warmest temperature setting.
Carefully feel the inlet and outlet heater hoses at the heater core. Is the inlet heater
hose significantly hotter than the outlet heater hose? If yes, go to step 10. If the
hose temperature feels approx. the same, go to the next step.
4. Test the operation of the A/C compressor clutch. Does the A/C compressor clutch
engage? If yes, go to step 6. If the compressor clutch does not engage, go to step
5.
5. Inspect A/C compressor clutch and controls. Repair or replace as needed, go to
step 13.
6. Determine if the A/C system is operating within specifications. If yes, go to step 8. If
no, go to step 11.
7. Check the low engine temperature problem. Repair any problems found, go to step
13.
8. Inspect for correct operation of the recirculation door. If the door is operating
correctly, go to step 13. If the door is not operating properly, go to step 12.
9. Check air delivery system. Repair any problems found, go to step 13.
10. Check the heater core for blockage. Repair or replace as needed, go to step 13.
11. Check A/C performance. Repair or replace as needed, go to step 13.
12. Repair the recirculation door concern. When the repair is complete, go to step 13.
13. Operate the system in order to verify the repair. If the system is operating properly,
the procedure is complete. If the system is still not providing proper defrosting,
repeat the entire test.

Noise from Blower Motor

1. Inspect the air inlet grille for debris. If the grille has debris, go to step 7. If the grille
is clear, go to the next step.
2. From inside the vehicle, close all vehicle doors and windows, turn ON the ignition,
with the engine OFF, and cycle the blower motor through all speeds in order to
determine where and when the noise occurs. If noise is heard during the blower
operation, go to step 3. If there is no noise, go to step 10.
3. Inspect for excessive vibration at each blower motor speed by feeling the blower
case. If there is vibration, go to step 5. If no vibration is present, go to the next step.