Pinpoint Test D: Insufficient, Erratic Or No Heat

Climate Control System


Pinpoint Tests


Pinpoint Test D: 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 D: INSUFFICIENT, ERRATIC OR NO HEAT

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D1 CHECK FOR CORRECT ENGINE COOLANT LEVEL


- Ignition OFF.
- Check the engine coolant level when hot and when cold.
- Is the engine coolant at correct level (hot and cold) as indicated on the engine coolant recovery reservoir?

Yes
GO to D3.

No
GO to D2.

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D2 CHECK THE ENGINE COOLING SYSTEM FOR LEAKS


- Pressure test the cooling system for leaks. Refer to Cooling System.
- Does the engine cooling system leak?

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

No
GO to D3.

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D3 CHECK FOR HOT COOLANT TO THE HEATER CORE INLET HOSE


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




- For auxiliary system: 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 D4.

No
GO to Cooling System.

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D4 CHECK THE HEATER CORE OUTLET HOSE FOR HOT COOLANT


- For main system: Using a suitable temperature measuring device, measure the heater core outlet hose temperature.




- For auxiliary system: 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 I. Pinpoint Test I: Temperature Control Is Inoperative/Does Not Operate Correctly

No
CARRY OUT the Heater Core Component Test. REFER to Heater Core under Component Tests to determine whether a plugged or partial plugged condition exists. Testing and Inspection

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