Heater Control Valve

This component is part of Heating System.


The heater control valve controls the flow (on/off) of the radiator fluid to the heater core inside the cabin. It is a simple brass valve which is controlled by the heat slider lever on the dash. This brass valve has a rubber o-ring located on the upper section of the valve.

Heater Valve O-Ring Replacement

If the heat inside the car doesn’t want to shut off, it could be that the o-ring on the heater valve needs to be replaced. The following procedure will help you to replace this rubber o-ring…

1. Remove the heater valve access cover. This is the large rubber/plastic cover on the firewall, above the return heater hose.

2. Stuff a rag around the valve and ensure that the rag is positioned all the way around the valve. This will help to catch anything that may get away from you. If you drop any tools or parts into this access hole, you will need to remove the fan box and possibly the entire heater core to retrieve your lost items.

3. Take some pictures and make note of the position of the valves arm as well as the position of the heat sliders inside the car. Either slide the heat to the fully on or fully off position. Again make note and take pictures of the valves arm position under the access cover. You want to reinstall in this same position.

4. Carefully pry off the rod connected to the top of the valve arm and set off to the side.

5. Carefully unscrew the screw that holds the valve arm and remove the arm.

6. Use a long metal screw (screw threads = 4 x 0.7 mm) and carefully screw this into the hole of the valve (refer to picture in step 13 below). This will help to pull the valve from the core. Before starting to pull up on the screw (valve), tie a string on the end of the screw. Secure the opposite end of the string to a stationary point (ie wiper arm). This is to help ensure that the valve doesn’t fall into the core. If the valve falls into the core, the core will need to be removed from the car.

7. Carefully tap down on the screw to lower the valve so that the metal stop plate can be removed from the side slit in the core.

8. Make note of the exact position of the stop plate. It will need to be reinstalled in this same position.

9. Remove the screw and slide the metal stop plate out. Screw the screw back into the valve.

10. Carefully pull up on the screw/valve to remove it from the core. You may need to use a pair of pliers to assist with removal.

11. Once the valve is out, take to the bench and remove the old rubber o-ring and clean up all parts.

12. Install new rubber o-ring (PN# xxx). Also lube the valve ad o-ring with some plumbers grease. This helps to slide the valve back into the heater core.

13. Reinstall the valve (with the long screw secured with the string).

14. Ensure that the valve is installed in the same position as when you removed it. With the new rubber o-ring, the fit should be nice and tight as you slide it into position. Carefully remove the long screw. Again, the valve should hold in place with the friction of the new o-ring.

15. Carefully install the metal stop plate & on/off arm in same position as when you removed it.

16. Carefully install the on/off rod onto the arm.

17. Remove the rag and reinstall the rubber/plastic cover on the firewall.

18. Congratulations! You are finished!