Pinpoint Test G: Insufficient, Erratic or No Heat

Climate Control System

Pinpoint Tests

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

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G1 CHECK FOR CORRECT ENGINE COOLANT LEVEL


- Ignition OFF.
- Check the engine coolant level.
- Is the engine coolant at the correct level as indicated on the engine coolant recovery reservoir?

Yes
GO to G3.

No
GO to G2.

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G2 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
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 G3.

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G3 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 temperature above 65.5°C (150°F)?

Yes
GO to G4.

No
REFER to Engine Cooling Testing and Inspection to diagnose the engine not reaching normal operating temperature.

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G4 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 G and DIAGNOSE for a blend door actuator.

No
INSTALL a new heater core. REFER to Climate Control Service and Repair. TEST the system for normal operation.

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