2002 F150 SC. I have a similar problem to others, but all efforts mentioned before in previous threads have not remedied the problem. I have functional heat with my EATC (Electronic Auto Temp Control). My problem lies with no or very low air flow to floor setting, it diverts to defrost. The dealer told me my EATC control unit was bad, and I have a hard time accepting that. I put a used EATC unit in that is functioning properly from another vehicle, and I have the same problem. Also, no diagnostic problem codes come up with either EATC unit installed. After reviewing data and diagrams from the ALLDATA website for my vehicle, I am questioning the panel/floor door vacuum control motor, and am hoping anyone could shed some light on this. Two different dealerscould not figure this out, and each continually charge me diagnosis charges, even when they don't find the right fix. Any help?

 

Have you tried a new or different vacuum control motor? Or watch it work when you send the command to it and see what it is doing.