I'm not a mechanic / technician but it sounds like your engine cooling
thermostat is sticking open ( assuming that the electric engine cooling fans
are not running continuously )
I would expect a plugged heater core.Take your hand and feel the two heater hoses that pass thru the firewall on the passenger side; if one is hot and the other is much cooler, than you heater core is plugged and needs replacement.
This would indicate that the system is low on coolant when the gauge is hot. Not enough coolant to service the heater core.
thermostat
change t.stat
If the coolant level is okay, I would suspect a restricted heater core. Try flushing the heater core.
sounds like your water pump ain't pumping, don't drive it till it is!. could be as simple as a new fan bewlt or might even need a pump
Check coolant level..... hot coolant runs through the heater core and the blower motor blow air across it to create hot air........most likely a failing thermostat and. Possibly a water pump on its way out.
Your low on coolent! system set up to protect engine first so routs coolent away from heater.
there is a short somewhere in dash or heater, you need to fix that to stop fuses blowing
I should be able to answer your question if you say which YEAR of Ford Windstar ( I was looking at the 1996 Ford Windstar owners manual and it doesn't have any warning lights above the engine temperature gauge )
Could be the temperature sending unit.See "Related Questions" below for more specifics...
Check coolant level