PINPOINT TEST L : Insufficient, Erratic, or No Heat: Notes

Normal Operation and Fault Conditions 

Warm coolant flows from the engine through the heater core and back to the engine. Proper coolant temperatures are critical for good heater performance.

Possible Sources 

• Missing or broken engine coolant hose check valve or incorrect orientation of check valve (3.5L only)
• Plugged or partially plugged heater core
• Low engine coolant level
• Temperature blend door actuator(s)
• Temperature blend door(s) binding or stuck