Ford winstar 2001 has intermittent heater-defrost goes cold then hot , ideas for repair ?

It sounds like the blend door actuator is failing. This is a pretty common thing to happen on these vehicles. The part itself is not very expensive from the dealer. Access to it on this particular vehicle, requires only the removal of the radio and the HVAC control panel, so labour to replace it shouldn't be very expensive either. Hope this helps.