Originally Posted by 98range
I have a 98 ranger with the four port valve. A vacuum line connects to the valve. What makes the valve open or close? Does it close off the coolant into the heater core when closed?
The vacuum makes it open/close (not sure which). Depending on the position of the temperature selector and climate control selector (the thing you turn to A/C, defrost,etc), vacuum will be applied.
It does block the coolant from the heater core when closed.