Heater Control Valve Replacement

How to Replace a Heater Control Valve

For heat to enter your vehicle, hot engine coolant needs to enter the vehicle’s heater core. However, that flow of hot coolant needs to be regulated or you would have heat entering the vehicle at all times. Some vehicles use a blend air door to stop heat from entering the vehicle. Other vehicles have a heater control valve.

The heater control valve is nothing more than a valve that is closed and opened by a cable when you change your controls in the vehicle from cold to hot. At that point, like a spigot in your house, coolant is allowed to flow through the heater core. From the hot coolant, the core gets hot and allows heat to enter the vehicle.

Like any other mechanical component, heater control valves go bad. Some will actually develop enough corrosion on them that you can’t open and close it. As a result, you get no heat in the vehicle. Others can begin to leak coolant. Regardless, they are easy to replace and not very expensive.

Parts and Supplies needed to Replace a Heater Control Valve

1. Coolant

2. New Heater Control Valve

3. New Hose Clamps

4. New Heater Hose (optional)

5. Protective Clothing

6. Eye protection

Tools Needed to Complete this Job

1. Screwdriver

2. Pliers

3. Large Drain Pan to Collect Used Coolant


Step 1. Park the vehicle on a flat surface, place the parking brake on, and place the vehicle in park (A/T) or in reverse (M/T)

Step 2. Allow the engine to fully cool so that the radiator is cool to the touch.

Step 3. Locate the radiator drain plug on the lower section of the radiator. It will look like a wing nut. Place the large drain pan under it and drain approximately half of the coolant from the radiator.

Step 4. Place the coolant in a safe place to be reused. NOTE: Animals are attracted to coolant. It can be fatal if they drink it, so make sure to keep it out of their reach.

Step 5. Locate the heater control valve. Most are near the firewall of the vehicle on the passenger’s side of the vehicle. It will have heater hose attached to both sides. The valve will have a cable attached to it for operation.

Step 6. Loosen the clamps that attach the heater hose to the control valve. NOTE: Some coolant will still be in the hose.

Step 7. Once you remove the hose clamps, twist the rubber heater hose where it attaches. Pliers usually make this job easier. While twisting, pull the hose from the valve.

Step 8. Once the heater hoses are removed, disconnect the heater valve control cable.

Step 9. OPTIONAL This is the perfect time to replace old or damaged heater hose. If it appears to be original, is in poor condition, or is leaking, disconnect the hose from the engine and replace it.

Step 10. If you are reusing the original heater hose, make sure it is clean and free of corrosion. Replace the old hose clamps by placing them on the heater hose before installing the control valve.

Step 11. Install the control valve cable on the new heater control valve and fully push the heater hose on to the new valve.

Step 12. Tighten the new hose clamps and refill both the radiator and overflow bottle.

Step 13. At this point, start the engine and turn the heater on high so the valve is open and air can escape from the system.

Step 14. Replace the radiator cap, allow the engine to warm up to operating temperature, and check for leaks.

Best Practices

  • This is a good time to replace heater core hoses and clamps.
  • Never work on a the cooling system when it is hot.
  • Make sure the cable to the heater control valve is free and easy to move before attaching it to the new control valve. If tight, try to lubricate it or replace it.
If further assistance is needed, our certified car repair technicians are ready to answer your car questions. Also, gain manufacturer specific instructions and information by clicking - Auto Repair Manual

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Article first published (Updated 2015-01-09)