Hey folks new member here. Been driving fords since '66.
I have a '99 f150, 5.4ltr, auto, etc. Been a great truck but have a problem that stumps me. The AC puts out freezing cold air.....problem, when I pull off from stop, if the vaccumm drops only a bit the heat/cool shutter in the controller duct??? closes and switches to HEAT. If I drop the shifter down one from "D" and let it slow down with the trans, and the ac control switch is off, it will go back to original position (shutter) and then I can turn the control back on with cold air again. Very aggitating to say the least. Anyone have / had this problem? Suspect the temp control, (rotate from cold to hot) via ****. It shows a microprocessor in the wireing diagram which is part of this control. Anybody agree that this control may be bad? Also, in winter I have to take off (so the vac drops) to get it to go to heat mode, as it starts in AC mode, even with heat control over to heat side of control. It will stay in heat winter or summer unless i let the truck slow down so the vac increases to make it change again.
Let me add that I've never had any problem with AC OR HEAT except for this shutter control problem.