Non-Trouble Code Procedures

PRE-DIAGNOSTIC PREPARATIONS
Check the radiator coolant level, drive belt tension, engine vacuum line connections, radiator air flow, and radiator fan operation. Start engine and bring to normal running temperature.

CAUTION: If vehicle has been run recently, wait 15 minutes before removing cap, then place a rag over the cap and turn it to the first stop. Allow pressure to escape through the overflow tube and when the system stabilizes, remove the cap completely.

Temperature Reference Chart:

MAXIMUM HEATER OUTPUT: TEST AND ACTION
Engine coolant is provided to the heater system by two 16mm (5/8 inch) I.D. heater hoses. With engine idling at normal running temperature, set the control to maximum heat, floor, and high blower setting. Using a test thermometer, check the air temperature coming from the floor outlets.

If the floor outlet air temperature is insufficient, refer to Cooling System/Testing and Inspection to determine proper engine coolant temperature. Both heater hoses should be HOT to the touch (coolant return hose should be slightly cooler than the supply hose). If coolant return hose is significantly cooler than the supply hose, locate and repair engine coolant flow obstruction in heater system.
1. Possible location or cause of obstructed coolant flow are as follows:
a. Pinched or kinked heater hose (supply or return).
b. Improper heater hose routing
c. Plugged heater hoses or supply and return ports at cooling system connections.
d. Water valve (if equipped) stuck or inoperative
e. Plugged heater core
2. If proper engine coolant flow through heater system is verified and floor outlet air temperature is still insufficient, a mechanical problem may exist within the heater system. Possible location or cause of insufficient heat are as follows:
a. Obstructed cowl air intake
b. Obstructed heater system outlets.
c. Blend-air door not functioning properly
3. If temperature cannot be adjusted by the heater control settings and/or TEMP lever is difficult to move, possible location or cause are as follows:
a. Blend-air door binding
b. Control cables misrouted, pinched, kinked, or disconnected
c. Improper engine coolant temperature (refer to Pre-Diagnostic Preparations).