Pinpoint Test F : Insufficient, Erratic Or No Heat: Notes

Insufficient, Erratic Or No Heat 

Normal Operation and Fault Conditions 

When the engine is at operating temperature hot coolant flows from the coolant pump through the heater core and back to the coolant pump. Correct coolant temperatures are critical for good heater performance.

Possible Sources 

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

Visual Inspection and Diagnostic Pre-checks 

• Inspect for low engine coolant level.