My son has a 2000 Ford Taurus SEL w/auto heat/air. Recently HOT air starting coming from all ducts. A/C compressor lines are cold when on a/c but heat comes all the time. Not warm outside air but heater hot air. Is there something not letting the flow doors open/shut properly? Leaky vacuum line to heater/ac controller? Flapper door actuators problem? How to get in there to check? Please help!!!
The problem is most likely with the blend door actuator.
https://www.rockauto.com/catalog/moreinfo.php?pk=3763596&cc=1362822
Common problem on Fords.
The blend door actuator operates the blend door to control whether heated or cooled air enters the passenger cabin.
And if you go on YouTube, and enter in their search engine, “Taurus Blend Actuator”, you’ll see how to replace it.
Tester