For 1990-2009 cars

### Insufficient Heating of the Passenger Compartment

1. Inspect for the incorrect operation of the controls.

Advise the driver of the proper operation of the controls.

2. Inspect the engine for low engine coolant level.

Perform the following steps, as necessary:

• | Add coolant.

• | Inspect the engine for coolant leaks.

• | Run the engine in order to clear any air locks.

3. Inspect for a faulty engine thermostat.

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

4. Inspect for a kinked heater hose.

Perform the following steps, as necessary:

• | Straighten the heater hose.

• | Replace the heater hose. Refer to Heater Inlet Hose Replacement or Heater Outlet Hose Replacement .

5. Inspect for obstructed heater core tubes.

An obstruction usually causes a squishing noise in the heater core.

Perform the following steps, as necessary:

• | Remove any foreign material from the heater core.

• | Replace the heater core. Refer to Heater Core Replacement .

6. Inspect for one of the following conditions:

• | A faulty blower motor

• | Replace a faulty blower motor. Refer to Blower Motor and Fan Replacement .

• | A faulty blower circuit

• | Repair or replace faulty wires or connections.

### Insufficient Heating of the Rear Seat Area

1. Inspect for the incorrect operation of the controls.

Advise the driver to use high blower speed in order to force air into the rear of the passenger compartment.

2. Inspect for an obstruction on the floor.

Inspect for the following conditions under the front seat:

• | Bulky objects

• | Torn insulation

### Insufficient Heating

1. Inspect the duct work for the following conditions:

• | The proper installation

• | Obstructions

2. Inspect the blower operation.
3. Inspect the following components for the proper installation and the proper operation:

• | The temperature lever

• | The temperature motor