Pinpoint Test L: Insufficient, Erratic or No Heat

Climate Control System

Pinpoint Test L: Insufficient, Erratic or No Heat

Normal Operation

Under normal operation, warm coolant flows from the engine through the heater core and back to the engine.

This pinpoint test is intended to diagnose the following:
- Plugged heater core
- Coolant level
- Temperature blend door


PINPOINT TEST L: INSUFFICIENT, ERRATIC OR NO HEAT

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L1 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 L3.

No
GO to L2.

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L2 CHECK THE ENGINE COOLING SYSTEM FOR LEAKS

- Pressure test the cooling system for leaks. Refer to Engine Cooling Component Tests and General Diagnostics.

- Does the engine cooling system leak?

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

No
GO to L3.

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L3 CHECK FOR COOLANT FLOW TO THE HEATER CORE

- Run the engine until it reaches normal operation temperature. Select the FLOOR position on the control assembly. 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 hot?

Yes
GO to L4.

No
REFER to Engine Cooling Cooling System to check cooling system function.

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L4 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
For EMTC systems, GO to Pinpoint Test P and diagnose for a temperature blend door actuator. Pinpoint Test P: Temperature Control is Inoperative/Does Not Operate Correctly For DATC systems, GO to Pinpoint Test Q and diagnose for a temperature blend door actuator. Pinpoint Test Q: The Blower Motor is Inoperative - EMTC

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

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