Heater Valve Woes

[Durwood]

So, I have an A/C cab with no A/C. All that's left in the engine compartment is the drier. There is no heater valve, as there isn't any vacuum to control it, so the hose goes straight to the core. Even when the fan's not on, that stupid thing is pouring heat into my cab, and it's the middle of summer...

What can I do? Do the non-A/C trucks have a manual heater valve or are they vacuum controlled, too? Any suggestions?

Thanks!