Re: Climate Control Under Load
It's a vacuum problem. The flaps in the system are controlled by vacuum servo motors, to which vacuum is ported via the climate control buttons (or knob). Pressing a button or turning the knob causes vacuum to operate the servo and move the flap(s) to direct the air where you want it. To ensure sufficient vacuum reserve to effectively operate the systerm, a vacuum reservoir (or tank) is used to hold a reserve supply of vacuum. This is located in the right front mudguard (I think!) and is "charged" from the inlet manifiold via a check valve. If the valve dies, the vacuum level in the reservoir may drop depending on throttle opening and cause the flaps go stupid. It's meant to be as fully evacuated as possible to ensure that the servos work under most conditions.
What's happening possibly with your car is that while the vacuum level is continually changing with throttle activity, it is casuing the flaps to move. They do this slowly over a period of a few seconds usually. When you decelerate and the manifold vacuum goes high, your flaps return to normal. When you accelerate manifold vacuum drops and the flaps tend to adopt the position they do when the car is not running. With most Fords, that means that the windscreen outlets are the ones that work.
All that said, it may be too that one of the vacuum line "plugs" that connect to the climate control, or any vacuum line in fact, may have become disconnected. That too will disturb the vacuum supply. Can you hear any hisssing coming from anywhere behind the dashboard?