GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Alero Export 🢒 Engine 🢒 Engine Cooling 🢒 Heating Performance Diagnostic

Step

Action

Yes

No

1

Where you sent here from Too Cold in Vehicle?

Go to Step 2

Go to Too Cold in Vehicle in HVAC Systems - Manual

2
  1. Inspect the heating and cooling system for the following:
    2. • Low coolant level
    • Loose or worn accessory drive belt
    • Leaking or kinked radiator or heater hoses
    • Missing radiator filler cap pressure seal
    • Improper radiator filler cap operation
    • Refer to Loss of Coolant in Engine Cooling.
  2. Perform the necessary repairs.

Are the repairs complete?

Go to Step 3

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3

Start the engine and allow the engine to idle in PARK.

Does the engine reach normal operating temperature?

Go to Step 4

Go to Symptoms - Engine Cooling in Engine Cooling

4

Check the heater output temperature.

  1. Move the vehicle outdoors; ensure that the vehicle hood, doors and windows are closed.
  2. Accurately measure the outdoor air temperature.
  3. Allow the engine to warm to operating temperature.

    4. (Allow approximately 20 minutes for thorough warm-up.)

  4. Install a precision thermometer into the I/P center air outlet.
  5. Select the VENT position of the mode control button.
  6. Select the maximum high blower speed position.
  7. Turn the temperature control knob to the maximum hot position.
  8. Measure and record the temperature of the delivered air (heater output temperature) once the temperature stabilizes.
  9. Compare the temperature of the delivered air (heater output temperature) @ the appropriate outdoor air temperature, to those listed:
    10. • 49°C (120°F) @ -18°C (0°F)
    • 57°C (135°F) @ 0°C (32°F)
    • 60°C (140°F) @ 10°C (50°F)

Is the delivered air temperature (heater output temperature) within the acceptable values?

Go to Step 5

Go to Step 6

5
  1. Inspect the following areas of the vehicle for cold air leaks:
    2. • Cowl
    • Air inlet valve
    • HVAC module case
  2. Make any necessary repairs.

Are the repairs complete?

Go to Step 12

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6
  1. Start the engine and allow to idle.
  2. Depress the mode control button until the LOWER position is displayed.
  3. Select the lowest blower speed position.
  4. Turn the temperature control knob to the maximum hot position.
  5. Check the temperature of the heater inlet and outlet hoses by feel.

    6. The air temperature around the hoses must be at least 24°C (85°F).

Does the heater inlet hose feel warm and the heater outlet hose feel cold?

Go to Step 7

Go to Step 10

7

Check the thermostat for proper installation and seating. Refer to Engine Coolant Thermostat Replacement in Engine Cooling.

Is the thermostat installed and seated properly?

Go to Step 9

Go to Step 8

8

Reinstall the thermostat correctly. Refer to Engine Coolant Thermostat Replacement in Engine Cooling.

Is the repair complete?

Go to Step 6

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9

Install a new thermostat. Refer to Engine Coolant Thermostat Replacement in Engine Cooling.

Is the repair complete?

Go to Step 12

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10
  1. Backflush the heater core.
  2. Drain and replace the coolant. Refer to Cooling System Draining and Filling in Engine Cooling.
  3. Start the engine and allow to idle.
  4. Depress the mode control button until the LOWER position is displayed.
  5. Select the lowest blower speed position.
  6. Turn the temperature control knob to the maximum hot position.
  7. Check the temperature of the heater inlet and outlet hoses by feel.

    8. The air temperature around the hoses must be at least 24°C (85°F).

Do both the heater inlet hose and the heater outlet hose feel warm?

Go to Step 11

Go to Step 12

11

Replace the heater core. Refer to Heater Core Replacement .

Is the repair complete?

Go to Step 12

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12
  1. Install components or connectors which were removed or disconnected.
  2. Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Symptoms - HVAC Systems - Manual in HVAC Systems -Manual