Heater Control Valve: Testing and Inspection

Heater Valve

Heater Valve Location:

1. Start the engine and warm up to normal operating temperature.
2. Depress the DEFROST function button.
3. Remove the vacuum line from the heater valve vacuum element.

Vacuum should not be present at the vacuum line. If vacuum is present repair the vacuum system.
The valve must be fully open and the coolant hoses at both sides of the valve should be equally hot.

If the vacuum system is in order but hot coolant is not present at both sides of the valve, the valve may be plugged or defective. Remove the valve for inspection and replace or repair as necessary.

4. Depress the CENTER air distribution button.
5. Adjust the temperature wheel to "MIN".
6. Depress the normal A/C button.

Vacuum should be present at the vacuum line. If vacuum is not present repair the vacuum system.
The valve must be fully closed and a noticeable temperature difference should be present at the inlet and outlet coolant hoses.

If the vacuum system is in order but hot coolant is present at both sides of the valve, the valve may be stuck or defective. Remove the valve for inspection and replace or repair as necessary.