A blocked heater hose could cause a leak. A stopped up heater core could as well. Or the connector in the Windstar could be cracked.
If you have lost a sufficient amount of coolant this will stop the heater working because there will be no hot water in the heater rad.
There could be multiple reasons why a heater would stop working in a truck. There could be low coolant or a bad fuse to make a heater stop working in a truck. The best way to find out the reason is to take it to a certified auto mechanic.
Could be a plugged heater core. Check the engine temp guage. if it is getting warm, your heater core could be plugged or restricted.
If the air conditioner in a Mitsubishi Legnum is not working, there could be a blown fuse. There could also be a loose cable, or a problem with the heater motor.
The heater core could be clogged up.
the heater core could be pluged or the heater control valve is stuck closed
You have to be more specific. What is not working?
Check the thermostat, also there could be a heater core issue...
If you are leaking coolant and there isn't enough to circulate into the heater core, perhaps the radiator cap could be partially responsible. Otherwise I'd suspect the thermostat, the heater valve or the water pump. But then, if it's the water pump the engine would probably be overheating.
Could be low on freon,
could be thermostat or heater fan if you can hear all the speeds on the blower motor working then it could be your thermostat but your heater core might be plugged as well