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:
- Engine overheating
- Plugged or partially plugged heater core
- Low engine coolant level
- Temperature blend door binding/stuck
- Temperature blend door actuator


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.
- 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 Engine Cooling Cooling System Draining, Filling and Bleeding. After filling and bleeding the cooling system, 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 Engine Cooling Component Tests and General Diagnostics.

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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 and diagnose for a temperature blend door actuator. Pinpoint Test I: Temperature Control is Inoperative/Does Not Operate Correctly

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

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