Pinpoint Test J: Insufficient, Erratic Or No Heat

Climate Control System

Pinpoint Tests

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

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J1 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 J3.

No
GO to J2.

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J2 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 J3.

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J3 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 J4.

No
REFER to Cooling System to check cooling system function.

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J4 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 K and diagnose for a blend door actuator. Pinpoint Test K: The Air Conditioning (A/C) Is Inoperative

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

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