Cold as in no heat?
Or cold as in AC?
Cold as in no heat can be done with heater by-pass valve in engine bay, so heater core has no more hot coolant flowing thru it
Some cooling systems don't need flow from one heater hose to the other, so you can just use one valve on one hose to stop flow thru heater core in the cab
BUT..........others NEED the flow from one heater hose to the other as coolant by-pass to/for water pump, in this case you need a by-pass valve that cuts off flow to heater core but maintains flow between the hoses
Rangers used this type, has 4 hose connections not just 2
And you can use either type as a Temp control as well, not just an on/off valve like Rangers used it for
So you can adjust temp of heater core by increasing or decreasing flow thru it