Heater Valve Diagnosis

1. Start engine and allow to warm up.
2. Set at 60°F and Auto.
3. Feel hose from heater water valve to heater core. Hose should not be hot. This indicates that vacuum is applied to the heater water valve and that the water supply to the heater core is shut off. In any other position of the control panel,water should flow to the heater core. If not, check the heater water valve and vacuum supply hose.
4. Vacuum should be applied to heater water valve and water flow to the heater core should stop when in the Max A/C mode.