Coolant Heater Inoperative

Coolant Heater Inoperative

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

Circuit/System Description

The optional coolant heater is a heating element that mounts in the engine block in place of an existing anti-freeze plug. The coolant heater operates using an external 110 volt AC power source and is designed to warm the coolant in the engine block for improved starting in very cold weather. The coolant heater also helps reduce fuel consumption when a cold engine is warming up. The detachable AC power cord contains an internal thermal switch that opens, to prevent operation when the ambient temperature is warmer than -10°C (14°F), and closes at -18°C (0°F) to allow operation. The power cord is also equipped with a weather shield to protect the plug when not in use.

Reference Information
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Wiring Repairs (Wiring Repairs)

Circuit/System Testing

Note: The power supply cord will test open due to an internal thermal switch if the ambient temperature is warmer than -10°C (14°F). The thermal switch is designed to close when the ambient temperature is below -18°C (0°F).

1. Test the engine coolant heater for an open or short to ground.

• If open or shorted, replace the heater.

2. If the heater tests normal, replace the coolant heater power cord.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Coolant Heater Replacement (With LC9, L76,or L92) (Coolant Heater Replacement (With LC9, L76,or L92))Coolant Heater Replacement (With LY2, LMG, LY5, LY6 or LFA) (Coolant Heater Replacement (With LY2, LMG, LY5, LY6 or LFA))
* Coolant Heater Cord Replacement (With LY2, LY5 or LMG) (Coolant Heater Cord Replacement (With LY2, LY5 or LMG))Coolant Heater Cord Replacement (With LC9, LY6, L92 or LFA) (Coolant Heater Cord Replacement (With LC9, LY6, L92 or LFA))Coolant Heater Cord Replacement (With LY6) (Coolant Heater Cord Replacement (With LY6))