1. Start the engine.
2. Select the DEFROST mode.
3. Select the maximum blower speed.

Does sufficient air flow from the defroster outlets?

Go to Step 2

Go to Step 10

Measure the engine operating temperature.

Does engine reach normal operating temperature?

Go to Step 3

Go to Step 4

1. Select the minimum blower speed.
2. Select the maximum temperature setting.
3. Feel the temperature of the inlet and outlet hoses at the heater core.

Does the inlet hose feel warmer than the outlet hose?

Go to Step 5

Go to Step 12

Repair the low engine temperature concern. Refer to Engine Fails To Reach Normal Operating Temperature .

Is the repair complete?

Go to Step 14

--

Is the vehicle equipped with A/C?

Go to Step 6

Go to Step 14

Test the operation of the A/C compressor clutch.

Does the A/C compressor clutch engage?

Go to Step 8

Go to Step 7

Repair the A/C compressor clutch. Refer to HVAC Compressor Clutch Does Not Engage .

Is the repair complete?

Go to Step 14

--

Perform the A/C system performance test. Refer to Air Conditioning (A/C) System Performance Test .

Is the A/C system operating within the specifications?

Go to Step 9

Go to Step 11

Inspect for correct operation of the recirculation door.

Is the recirculation door operating correctly?

Go to Step 14

Go to Step 13

Repair the air delivery concern. Refer to Air Delivery Improper .

Is the repair complete?

Go to Step 14

--

Repair the A/C performance concern. Refer to Symptoms - HVAC Systems - Manual .

Is the repair complete?

Go to Step 14

--

Repair the heating concern. Refer to Heating Performance Diagnostic .

Is the repair complete?

Go to Step 14

--

Repair the recirculation door concern.

Is the repair complete?

Go to Step 14

--

Operate the system in order to verify the repair.

Does the system operate correctly?

System OK

Go to Step 1