OK here is a mystery; I need help on this one. On my 82 the AC and heat work very well they blow very cold and hot air. However let’s say you are driving down the street and go to pass someone, or at a stop light and press the gas to get up to speed, what happens when you do either one of these is if the air is coming out the upper and side vents it will switch over to the bottom vent. And when you let off of the gas will come back to the upper vents. I have checked all of the vacuum tubing and they hold vacuum like they should, I have checked the actuators and they hold their position as they should. So what would cause the vacuum to stop and let the door close under acceleration and come back open when reducing the acceleration to normal speed and just driving down the road? The Hg of the engine is steady at 21 under idle or run up to 3k to 4k RPMs. Is it possible that the vacuum is collapsing one of the tubes when this happens? Any help or suggestions on this, thanks.

 

If your headlights don't open or close normally I would suspect the relay valve is leaking real bad so your vacuum reservoir is only getting partially charged. So when you give it a heavy throttle the select door is defaulting to the middle position (between A/C and heater).