Heater control valve needed?

[xaircav]

I installed the heater that came in a box when I bought my truck after putting a 12 volt motor in it. I installed a cable operated control valve in the supply heater hose and the heater puts out adequate heat when the blower motor is on. When the blower is off and the valve is open the heater box is only warm to the touch. Will I need to shut off the hot water in the summer? I'd like to eliminate the control valve.