Q: Heater control valve

Hello. Typically the heater control valve is in the underhood area mounted near or on the engine compartment firewall. In that location just look for the valve plumbed into what are typically 3/4 flexible rubber heater hoses (often "molded" hoses), one hose "in", and one hose "out" of the valve. Until recently, these valves were mechanically operated via a cable. So, you might see a cable attached to a lever on your valve. With the trend to more electronic controls, on newer cars the valves can be controlled electronically, in which case you will see a wire and plug connection to the valve and no cable or lever. On older cars, sometimes the valves get sticky as the cable, sheath, and lever accumulate dirt and corrosion. You can lightly lubricate the cable and lever with an appropriate lubricant that is safe for rubber and plastics. If you have been directed to this valve because you suspect it is involved in a malfunction or repair issue, feel free to rely on YourMechanic to diagnose your heater control valve issue and help you with any needed repairs.