What does a heater control valve do? Do I need it? I have A/C but not sure if it works, belt is missing.
Heater control valve allows coolant to flow thru the heater core and back to the engine when u slide the heat control lever to the heat position. If u remove/ bypass it, coolant will flow thru heat core all the time - u may not want that in summer season. On the other hand, u can bypass it by inserting a coupling in the hoses or blocking them and no coolant to the core - no heat either.
You really don't need it, just bypass it. Not sure if you can buy a new one or if you really want to. I took mine out back in 77 when I drove my merc to Alaska. Definitely did not need it there. Haven't tried to install a new one but probably do have the old one laying around here somewhere. So no worries.
It really depends on how hot it gets outside where you are if you need it or not. The AC cars bypass it on full cold to keep heat out of the heater box. The heater core is lower than the evaporator and closer to the blower motor so heat from it does warm the airstream to some degree. I use a newer style plastic one like Frank does and my air works great when it's hot and my defrost will still function when it's chilly and the morning dew covers the windshield
Does your car have functioning/working air conditioning? If it does...you need one. If you don't...you don't.
