I own a 1997 Ford Contour and there was a recall a few years ago on the heater blower and resistor. Check out the recalls on the car.
Bad blower motor? Blown blower motor fuse? Bad fan switch? Bad blower resistor pack?
Likely heater core. I had same problem with 1996 S-10 with 4.3L.
Same thing that causes other fuses to blow. Too much current through the fuse. A hot wire short to ground. Possibly a short made from a water leak.
The blower on the back heater may need to be replaced on the 2000 Ford Winstar.
Either the Heater Control Valve is not opening or the BLEND doors aren't opening BOTH could b due 2 a Vacume leak going 2 either one.OR the heater core could b blocked.
Cause its broke!
replace anti-freeze, replace thermostat
Blocked heater core, faulty heater valve, disconnected connection to the heater valve.
Perhaps a stuck door in the HVAC system or a blockage in the ducts.
When your tail lights are out you can simply replace them. If they continue to blow, you may have an electrical problem.
Most likely the bad news that you did not want to hear. The heater core is leaking coolant.