How do I check if my heater control valve is working the way its supposed to.
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1998 Toyota Tacoma
Answer #1patrick mannion from Greg Solow's Engine Room, December 09, 2009, 19:18Master
The heater control valve is right in the center rear of the engine compartment on the firewall. It is black plastic with two hoses going to it and a cable. Get a friend to move the heater control lever from max cold to max hot and see that the valve operates through its full range. The engine doesn't have to be on to test it this way. Start the engine get warm operate to the Hot position both hoses should feel hot. Is your Thermostat OK?