GM Service Manual Online
For 1990-2009 cars only
Table 1: Inadequate Defrosting
Table 2: Inoperative Blower
Table 3: Heating Insufficient
Table 4: Cold Drafts on the Floor

Inadequate Defrosting

Problem

Action

Obstruction in defroster nozzle

  1. Inspect both of the defroster nozzle outlets.
  2. Remove any foreign objects.
  3. Repair any loose instrument panel pads that block an outlet.

Damaged defroster nozzle outlet

  1. Carefully reshape the outlet flange with pliers so that the outlet opening is uniform.
  2. If the outlet flange cannot be reshaped, replace the air distributor.

Faulty mode actuator

  1. Inspect the operation of the defroster air valve.
  2. Replace the faulty mode actuator.

Insufficient heat

Refer to Insufficient Heating of Passenger Compartment in the following charts.

Inoperative Blower

Problem

Action

Blown fuse

Replace the fuse.

Open circuit

  1. Inspect the circuit between the ignition switch and the blower motor, and the blower motor ground circuit.
  2. Repair as necessary.

Faulty blower switch

Replace the faulty blower switch.

Heating Insufficient

Problem

Action

Incorrect operation of controls

Advise the driver of the proper operation of the controls.

Low engine coolant level

  1. Add coolant as needed.
  2. Inspect for coolant leaks.
  3. Run the engine in order to clear any air locks.

Faulty engine thermostat

  1. Inspect the thermostat.
  2. Replace the thermostat if necessary.

Kinked heater hose

  1. Inspect the hoses.
  2. Straighten any kinks in the hoses.
  3. Replace the hoses as necessary.

Obstructed heater core tubes

  1. Listen for a swishing noise in the core.
  2. Remove any foreign material from the core.
  3. Replace the core if necessary.

Faulty blower motor or blower circuit

  1. Repair or replace any faulty wires or connections.
  2. Replace the faulty blower motor.

Faulty heater water valve or solenoid or control circuit (if equipped)

  1. Inspect the water valve in order to ensure that the water valve closes when you move the temperature control to the coldest setting.
  2. If the water valve does not open, inspect the electrical connections between the control head and the solenoid, and the vacuum line connections between the engine and the solenoid, and the solenoid and the water valve.
  3. Ensure that the water valve opens when you move the temperature control several notches off of the coldest setting.

Cold Drafts on the Floor

Problem

Action

Partially open air inlet valve

  1. Ensure that the air inlet valve is properly closed in all modes except the recirculation mode.
  2. Repair the valve if necessary.

Side door seals damaged or missing

  1. Inspect all of the door seals.
  2. Repair or replace faulty seals as necessary.