Operation CHARM: Car repair manuals for everyone.

Heater Core Coolant Circulation Test

Perform the following test to verify that the climate control system is unable to produce a heater outlet duct air temperature exceeding 40°C (104°F) before replacing the heater core.

1. Run the engine at approximately 2000 rpm until "Normal" coolant temperature is reached.

2. Press red arrow on the climate control system panel repeatedly until the display changes to HI. Turn the fan knob clockwise until the fan speed bar graph shows the maximum fan speed.





3. Move the driver seat fully rearward, and place the probe of an electronic thermometer in the left hand footwell outlet duct, ensuring that the probe is fully in the hot air stream and not in contact with the duct (Illustration 1).

4. Maintain the engine speed at 2000 rpm, allow the temperature reading to stabilize.

5. Switch off the engine, return the seat to its normal position.

If the output air temperature reading is less than 40°C (104°F), the coolant circulation rate through the heater core is unsatisfactory. Continue with the procedures detailed.

If the output air temperature exceeds 40°C (104°F), the heater core performance is satisfactory - stop, do not continue.