Climate Control System - Vehicles With: Dual Automatic Temperature Control (DATC)

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

Wiring, terminals or connectors Temperature door actuator(s) Air trapped in the coolant system Heater core

Visual Inspection and Diagnostic Pre-checks

Inspect for low engine coolant level.

PINPOINT TEST F : INSUFFICIENT, ERRATIC OR NO HEAT

F1 CHECK FOR CORRECT ENGINE COOLANT LEVEL

Ignition OFF. Check the engine coolant level.

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

F2 CHECK THE ENGINE COOLING SYSTEM FOR LEAKS

Pressure test the cooling system for leaks. Refer to the appropriate section in Group 303 for the procedure..

Does the engine cooling system leak?

F3 CHECK FOR COOLANT FLOW TO THE HEATER CORE

Run the motor until it reaches normal operating temperature. Select the floor position on the control assembly. Set the temperature control to full warm and the blower to the lowest setting. Increase engine speed to 3,500 RPM and hold for 30 seconds. Allow the engine to idle for 30 seconds. Using a suitable temperature measuring device, check the heater core inlet hose to see if it is hot.

Is the heater core inlet hose hot?