Diagnostic Routine J

Diagnostic Routine J

Diagnostic Overview

Insufficient, Erratic or No Heat

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.

Visual Inspection and Diagnostic Pre-checks

- Inspect for low engine coolant level

Pinpoint Test

1. CHECK FOR CORRECT ENGINE COOLANT LEVEL

1. Ignition OFF.

2. Check the engine coolant level.

Is the engine coolant at the correct level as indicated on the engine coolant recovery reservoir?








2. CHECK FOR COOLANT FLOW TO THE HEATER CORE

1. Run the engine until it reaches normal operating temperature. Select the floor position. Set the temperature control to full warm and the blower to the lowest setting.

2. Using a suitable temperature measuring device, check the heater core inlet hose to see if it is hot.

Is the heater core inlet hose temperature above 66 C (150 F)?








3. CHECK FOR A PLUGGED OR RESTRICTED HEATER CORE

1. 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 C (43 F) - 17 C (63 F))?