GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2000 🢒 Century (China) 🢒 HVAC 🢒 Heating, Ventilation and Air Conditioning 🢒 Heating Insufficient

Step

Action

Value(s)

Yes

No

1
  1. Inspect the engine coolant level.
  2. Inspect the coolant pump drive belt tension.
  3. Inspect the radiator and the heater hoses for leaks and kinks.
  4. Inspect the radiator cap for proper operation.

Is the action complete?

--

Go to Step 2

--

2
  1. Set the mode to HEAT.
  2. Set the blower speed to HI.
  3. Set the temperature control to full HOT.
  4. Turn the ignition switch to ON.
  5. Inspect for airflow out of the heater outlet.

Is the airflow low or no airflow out of the heater outlet?

--

Go to Step 3

Go to Step 8

3

Inspect for airflow out of defroster or vent outlets.

Is the air flow low or no airflow out of the defroster or vent outlets?

--

Go to Step 4

Go to Step 15

4
  1. Set the mode control to DEFROST.
  2. Inspect for airflow out of the defroster outlets.

Is the air flow low or no airflow out of the defroster outlets?

--

Go to Step 5

Go to Step 16

5

Turn the blower speed from the following positions:

  1. OFF to LO
  2. MED-LO
  3. MED-HI
  4. HI
  5. OFF

Does the blower motor speed increases at each speed level when blower speed is turned to HI and then decreases as the switch is moved towards LO?

--

Go to Step 6

Go to Step 17

6
  1. Inspect for system obstructions at blower inlet and plenum.
  2. Repair as necessary.

Is the action complete?

--

Go to Step 7

--

7
  1. Turn the blower speed to HI.
  2. Turn the temperature control from full HOT to full COLD.

Did you hear any airflow changes?

--

Go to Step 25

Go to Step 24

8

Turn the blower speed from the following positions:

  1. OFF to LO
  2. MED-LO
  3. MED-HI
  4. HI
  5. OFF

Does the blower motor speed increases at each speed level when blower speed is turned to HI and then decreases as the switch is moved towards LO?

--

Go to Step 9

Go to Step 17

9
  1. Turn the blower speed to HI.
  2. Inspect the ambient air temperature with the thermometer.
  3. Drive the vehicle at 48 km/h (30 mph). The minimum engine warm-up time: 20 minutes.
  4. Check the following discharge air temperature at heater outlet temp @ ambient temp:
    5. • 54°C (130°F) @ -18°C (0°F)
    • 59°C (139°F) @ -4°C (25°F)
    • 64°C (147°F) @ 10°C (50°F)

Is the heater outlet temperature within specified value?

--

Go to Step 18

Go to Step 10

10

Cycle the temperature door actuators (CJ4 only).

Did the temperature door actuators properly function?

--

Go to Step 11

Go to Step 19

11
  1. Set the temperature control to full HOT.
  2. Start the engine.
  3. Feel the inlet and the outlet heater hoses.

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

--

Go to Step 14

Go to Step 12

12
  1. Disconnect the heater hoses at heater core.
  2. Inspect for proper heater hose location.

Is the heater hoses location reversed?

--

Go to Step 20

Go to Step 13

13
  1. Flush the heater core.
  2. Drain and refill the cooling system.
  3. Set the temperature control to full HOT.
  4. Start the engine.
  5. Feel the inlet and the outlet heater hoses.

Does the inlet heater hose fool hot and the outlet heater hose feel warm?

--

Go to Step 26

Go to Step 23

14
  1. Inspect the thermostat for proper installation.
  2. Repair as necessary.

Is the thermostat properly installed?

--

Go to Step 22

Go to Step 21

15
  1. Inspect the mode door control and the stepper motors.
  2. Repair as necessary.

Is the action complete?

--

Go to Step 26

--

16
  1. Inspect for obstructions in heater outlet.
  2. Repair as necessary.

Is the action complete?

--

Go to Step 26

--

17
  1. Inspect the blower motor. Refer to HVAC Blower Controls System Check .
  2. Repair as necessary.

Is the action complete?

--

Go to Step 26

--

18
  1. Inspect the vehicle for cold air leaks at the following areas:
    2. • The IP
    • The heater case
    • The front vents
  2. Repair as necessary.

Is the action complete?

--

Go to Step 26

--

19

Repair or replace the temperature door stepper motors.

Is the action complete?

--

Go to Step 26

--

20

Reinstall the heater hoses in correct location.

Is the action complete?

--

Go to Step 26

--

21

Reinstall the thermostat.

Is the action complete?

--

Go to Step 26

--

22

Replace the thermostat.

Is the repair complete?

--

Go to Step 26

--

23

Replace the heater core.

Is the repair complete?

--

Go to Step 26

--

24
  1. Inspect the temperature door stepper motors. Refer to Temperature Control Inoperative or Driver Temperature Control Inoperative or Passenger Temperature Control Inoperative .
  2. Repair as necessary.

Is the action complete?

--

Go to Step 26

--

25
  1. Inspect for system obstructions between blower and system outlets.
  2. Repair as necessary.

Is the action complete?

--

Go to Step 26

--

26

Perform the functional test. Refer to Functional Check .

Is the action complete?

--

System OK

--