Pinpoint Test K: Insufficient, Erratic or No Heat

Climate Control System

Pinpoint Test K: Insufficient, Erratic or No Heat

Normal Operation

Under normal operation, coolant flows from the engine through the heater core and back to the engine. Proper coolant temperatures are critical for good heater performance.

This pinpoint test is intended to diagnose the following:

- Plugged or partially plugged heater core

- Low engine coolant level

- Temperature blend door actuator(s)

- Temperature blend door(s) binding or stuck

PINPOINT TEST K : INSUFFICIENT, ERRATIC OR NO HEAT

K1 CHECK FOR CORRECT ENGINE COOLANT LEVEL

- Ignition OFF.

- Check the engine coolant level when hot and cold.

Is the engine coolant at the correct level (hot/cold) as indicated on the engine coolant recovery reservoir?

Yes
GO to K3.

No
GO to K2.

K2 CHECK THE ENGINE COOLING SYSTEM FOR LEAKS

- Pressure test the cooling system for leaks.

Does the engine cooling system leak?

Yes
REPAIR the engine coolant leak. TEST the system for normal operation.

No
FILL and BLEED the cooling system. REFER to Cooling System &/or Engine Block Heater, After filling and bleeding the cooling system, GO to K3.

K3 CHECK FOR COOLANT FLOW TO THE HEATER CORE

- Run the engine until it reaches normal operation temperature. Select the FLOOR position. Set the temperature control to full warm and the blower to the lowest setting.

- Using a suitable temperature measuring device, check the heater core inlet hose to see if it is hot.

Is the heater core inlet hose temperature above 65.5°C (150°F)?

Yes
GO to K4.

No
REFER to check cooling system function.

K4 CHECK FOR A PLUGGED OR RESTRICTED HEATER CORE

- Using a suitable temperature measuring device, measure the heater core outlet hose temperature.

Is the heater core outlet hose temperature similar to the inlet hose temperature (within approximately 6-17°C [10-30°F])?

Yes
GO to Pinpoint Test O and diagnose for a blend door actuator. Pinpoint Test O: Temperature Control is Inoperative/Does Not Operate Correctly

No
INSTALL a new heater core. TEST the system for normal operation.