GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1998 🢒 Metro 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Heating Insufficient

Step

Action

Value(s)

Yes

No

1
  1. Inspect the engine coolant level. Refer to Coolant Concentration Testing in Engine Cooling.
  2. Inspect the coolant pump drive belt tension. Refer to Drive Belt Replacement 1.0L or Drive Belt Replacement 1.3L in Engine Mechanical.
  3. Inspect the radiator and the heater hoses for leaks and kinks. Refer to Cooling System Leak Testing in Engine Cooling.
  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 HIGH.
  3. Set the temperature control to full HOT.
  4. Turn the ignition switch to ON.
  5. Test for airflow from the heater outlet.

Is little or no air flowing from the heater outlet?

--

Go to Step 3

Go to Step 9

3
  1. Perform Air Delivery Improper .
  2. If you cannot locate the airflow problem, inspect for airflow out of the defroster or the vent outlets.

Is little or no air flowing from the defroster or the vent outlets?

--

Go to Step 4

Go to Step 17

4
  1. Set the mode control to DEFROST.
  2. Test for airflow from the defroster outlets.

Is little or no air flowing from the defroster outlets?

--

Go to Step 5

Go to Step 18

5

Turn the blower speed switch from OFF to each of the following settings:

  1. LOW
  2. MEDIUM 1
  3. MEDIUM 2
  4. HIGH
  5. Return the switch to OFF

Does the blower motor speed increase at each speed level when you advance the selector switch towards HIGH, and decrease at each speed level when you advance the selector switch towards LOW?

--

Go to Step 6

Go to Step 19

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

Is the repair complete?

--

Go to Step 7

--

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

Did you hear any airflow changes?

--

Go to Step 8

Go to Step 21

8

Inspect for system obstructions between the blower and the system outlets.

Is the action complete?

--

Go to Step 25

--

9

Turn the blower speed switch from OFF to each of the following settings:

  1. LO
  2. MEDIUM 1
  3. MEDIUM 2
  4. HIGH
  5. Return the switch to OFF

Does the blower motor speed increase at each speed level when you advance the selector switch towards HIGH, and decrease at each speed level when you advance the selector switch towards LOW?

--

Go to Step 10

Go to Step 19

10
  1. Turn the blower speed switch to HIGH.

    2. Caution: The cooling system is pressurized when hot.

  2. With the engine cold, remove the radiator cap.
  3. Start the engine and idle until coolant flow is visible inside the radiator.
  4. Install the radiator cap.
  5. Using a thermometer, record the ambient air temperature.
  6. Drive the vehicle at 48 km/h (30 mph) for a minimum of 20 minutes.
  7. Using the thermometer, record the discharge air temperature at the heater outlet.
  8. Using the following table, compare the heater outlet temperature with the ambient air temperature:
    9. • 54°C (130°F) at -18°C (0°F)
    • 59°C (139°F) at -4°C (25°F)
    • 64°C (147°F) at 10°C (50°F)

Is the heater outlet temperature within the specified values?

--

Go to Step 20

Go to Step 11

11
  1. Turn the ignition switch to LOCK.
  2. Test the temperature door operation by moving the temperature control quickly from COLD to HOT and back to COLD.

Did you hear the temperature door slamming at each end?

--

Go to Step 12

Go to Step 21

12
  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 does the outlet heater hose feel warm?

--

Go to Step 16

Go to Step 13

13
  1. Disconnect the heater hoses at the heater core.
  2. Inspect for proper heater hose location. Refer to Heater Hoses Replacement .

Are the heater hoses locations reversed?

--

Go to Step 14

Go to Step 15

14

Install the heater hoses in the correct location.

Is the action complete?

--

Go to Step 25

--

15
  1. Flush the heater core.
  2. Drain and refill the cooling system. Refer to Cooling System Draining and Filling in Engine Cooling.
  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 feel hot, and does the outlet heater hose feel warm?

--

Go to Step 25

Go to Step 24

16

Inspect the thermostat for proper installation. Refer to Engine Coolant Thermostat Replacement in Engine Cooling.

Is the thermostat installed properly?

--

Go to Step 23

Go to Step 22

17
  1. Inspect the mode door control cable and the linkages.
  2. Adjust the mode control cable. Refer to Mode Control Cable Adjustment .

Is the action complete?

--

Go to Step 25

--

18
  1. Remove the heater case. Refer to Heater Case Replacement .
  2. Inspect the heater outlet for an obstruction.
  3. Repair as necessary.

Is the action complete?

--

Go to Step 25

--

19

Refer to HVAC Blower Controls System Check for blower motor diagnosis.

Is the action complete?

--

Go to Step 25

--

20
  1. Inspect the vehicle for cold air leaks at the following locations:
    2. • The instrument panel
    • The heater case
    • The front vents
  2. Repair as necessary.

Is the repair complete?

--

Go to Step 25

--

21
  1. Inspect the temperature control cable and the linkages.
  2. Adjust the temperature control cable. Refer to Temperature Control Cable Adjustment .

Is the action complete?

--

Go to Step 25

--

22

Install the thermostat. Refer to Engine Coolant Thermostat Replacement in Engine Cooling.

Is the action complete?

--

Go to Step 25

--

23

Replace the thermostat. Refer to Engine Coolant Thermostat Replacement in Engine Cooling.

Is the action complete?

--

Go to Step 25

--

24

Replace the heater core. Refer to Heater Core Replacement .

Is the action complete?

--

Go to Step 25

--

25

Perform System Performance Test .

Is the action complete?

--

System OK

--