GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 1998 🢒 Isuzu MD Steel Tilt (F Model) 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Heating Insufficient
Table 1: Poor Defrosting
Table 2: No Heat (Blower Motor Working)
Table 3: Heater Gurgling Sound
Table 4: Poor Ventilation

Poor Defrosting

Problem

Action

  1. The door(s) which control airflow are not functioning correctly.
  2. The blower motor is not working.
  3. There is blockage in the defroster outlets.
  4. A restricted heater core and/or hoses.
  5. A faulty thermostat and/or radiator cap.
  6. There is blockage in front of the air conditioning filter.
  7. There is blockage in the path of the door.
  1. Determine and correct the cause of the malfunction.
  2. Determine and correct the cause of the malfunction. Refer to Blower Motor Inoperative at Any Speed .
  3. Remove the blockage.
  4. Flush the cooling system. Refer to Flushing .
  5. Determine and correct the cause of the malfunction. Refer to Thermostat Diagnosis .
  6. Clean the air conditioning filter. Refer to Passenger Compartment Air Filter Replacement .
  7. Remove the blockage.

No Heat (Blower Motor Working)

Problem

Action

  1. There is low engine coolant level.
  2. A faulty thermostat and/or radiator cap.
  3. A restricted heater core and/or hoses.
  4. A faulty actuator.
  5. The pivot shaft of door(s) is not seated correctly.
  6. There is blockage in front of the air conditioning filter.
  7. There is blockage in the path of the door.
  1. Check the engine coolant level. Refer to Cooling System Draining and Filling .
  2. Determine and correct the cause of the malfunction. Refer to Engine Coolant Thermostat Replacement .
  3. Flush the cooling system. Refer to Flushing .
  4. Check the actuator function and replace as necessary.
  5. Seat the pivot shaft of the door(s) correctly.
  6. Clean the air conditioning filter. Refer to Passenger Compartment Air Filter Replacement .
  7. Remove the blockage.

Heater Gurgling Sound

Problem

Action

  1. There is low engine coolant.
  2. A restricted heater core and/or hoses.
  1. Check the engine coolant level. Refer to Cooling System Draining and Filling .
  2. Flush the cooling system. Refer to Flushing .

Poor Ventilation

Problem

Action

  1. A blockage in the heater module.
  2. A blockage in the recirculating/fresh air duct.
  3. A binding or sticking of the recirculating/fresh air door.
  4. The recirculating/fresh air door is not operating.
  5. A faulty recirculating/fresh air actuator.
  6. The pivot shaft of the door is not seated correctly.
  1. Remove the blockage in the heater module.
  2. Remove the blockage in the recirculating/fresh air duct.
  3. Remove the blockage, repair and replace as necessary.
  4. Repair and replace the door as necessary.
  5. Seat the pivot shaft of the door.
  6. Seat the pivot shaft of the door(s).