What does the heater control valve do?
The heater control valve (sometimes called the hot water valve) is used to control the rate at which coolant flows through the heater core. The valve is located on the heater inlet hose. Manually operated systems may use a cable, a vacuum motor or an electric solenoid to operate the valve.
Can a bad heater control valve cause overheating?
Another symptom of a problem with the heater control valve or it’s hoses or connectors is a coolant leak. A coolant leak at the heater control valve is not only a problem in that it will disable the heater, but it will also compromise the cooling system which can cause the engine to overheat.
What happens if heater control valve is bad?
The heater may produce hot air, but only at certain times, such as at idle, and the hot air may come and go. A faulty heater control valve may also cause the temperature gauge to behave erratically, rapidly climbing and falling, which will make it difficult to determine the temperature of the engine.
Why is my heater control valve not working?
Depending on the amount of vacuum, the vacuum motor will close off the flow of engine coolant fully or partially. However, even if the heater control supplies vacuum the mechanical portion of the valve can fail, preventing the heater control valve from closing.
Where is the control valve on an A / C heater?
Heater Control Valve. It may be located on the inlet or the outlet port of the heater core, and activated by a cable, electronic control or a vacuum signal. This valve may be normally open, allowing coolant to flow until activated, or normally closed, allowing coolant to flow only when activated.
What causes coolant to leak out of a heater?
Over time the heater control valve can wear out and crack, which will cause coolant to leak from the valve. Heater control valves can also leak from excessive corrosion from contact with old or contaminated engine coolant.
What causes a vacuum to go out on a heater?
Since a vacuum operated valve defaults to the fully open heat-on position when vacuum isn’t applied, a loss of vacuum is the first thing to suspect in a “heat always on” condition. The loss of vacuum can be caused by a break in a vacuum line or a faulty vacuum switch. To repair a faulty switch, you sometimes have to replace the heater control.