What is the Coolant Vacuum Valve Switch all about?

During the winter, when a vehicle warms up and coolant begins flowing through the engine, it is not always flowing through the heater itself. The coolant begins flowing through the heater when the climate control knob is turned to the heater or defroster position. The climate control knob is generally attached to the vacuum hose which leads to the coolant vacuum valve switch.

When in the heater position, the coolant vacuum valve switch is opened and allows coolant from the engine to enter the heater unit, called the heater core. It is this warm coolant flowing off the engine into the heater core that gives off heat for the interior fan to blow through the vents. This is how heat works in many new vehicles.

Sometimes the coolant vacuum valve switch can crack or become clogged with debris or old coolant. In these instances, the vehicle may experience symptoms similar to that of another cooling system issue so the correct diagnosis is important.

Keep in mind:

The coolant vacuum valve switch is used to control flow to the vehicle’s heater core. Without this switch, a vehicle will have no heat in the winter.

How it's done:

• The Coolant Vacuum Valve Switch is verified that it needs to be replaced. The coolant is lowered until it is below the switch.
• The vacuum lines are disconnected and the defective Coolant Vacuum Valve Switch is removed from the intake manifold.
• The new Coolant Vacuum Valve Switch is installed into the manifold and the vacuum lines are reconnected.
• The coolant is refilled and bled of air. The Coolant Vacuum Valve Switch is tested for operation.
• The vehicle is tested to ensure proper operation of the Cooling System vacuum valve switch.

Our recommendation:

If you suspect the coolant vacuum valve switch has failed, contact one of our trained technicians to have it checked. Routine maintenance is also important for proper operation of the engine cooling system, which is where the heater unit obtains its heat.

What common symptoms indicate you may need to replace the Coolant Vacuum Valve Switch?

• Cold air blows through vents no matter which position the climate control knob is in
• Heat blows lukewarm
• Coolant leaking, either underneath the vehicle or in the passenger compartment

How important is this service?

While it may be easy to put off that coolant drip or wear an extra layer on the daily commute, if the heater isn’t properly running, the vehicle occupants will be very uncomfortable. Furthermore, the vehicle’s defrost unit won’t function properly, meaning that dangerous ice buildup could occur on the windows.