Re: 2000 Windstar Heater
First, back flush the heater core as it might be clogged (rust is the usual culprit). There is a kit you can get to implement your garden hose so you don't have to take it into a shop - but if you're unsure about doing uplevel jobs yourself, it's better to take it in for a full diagnostic check. With that said, if the core isn't clogged, then it is probably a door actuator problem. I'd get a Haynes or Chilton's manual as it's a tough job to tackle yourself, but you'll save $800 in labour costs alone.
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!