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

Normal Operation and Fault Conditions 

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

Possible Sources 

• Wiring, terminals or connectors
• Temperature door actuator(s)
• Heater core

Visual Inspection and Diagnostic Pre-checks 

• Inspect for low engine coolant level.