Subject:  warm air entering only when car in motion.
Is there a flap that can be adjusted that stops warm air from coming through the vents. This only happens when the car is moving.
If the lever that controls the direction of the airflow to the vents is all the way to the left position / white block, and you still are getting air through the vents when the car is moving, most likely you have a bad recirculation flap vacuum actuator. Normally this actuator uses engine vacuum to hold the flap closed when outside air is not wanted in the cabin. The flap is located above the fuse panel in the passengers footwell, covered by a black plastic grate. There is a small opening you can even stick a finger through to move the flap or to see its movement during operation of the climate control. You could also have other vacuum leaks in the
system that will not let this actuator do its job.
Check Greg Nichols page under "Climate Control" for all
the information to debug your problems......
'89 Black 5sp.
'00 Audi S4
Is there a flap that can be adjusted that stops warm air from coming
through the vents. This only happens when the car is moving.
The flap is there - this is the task of the fresh air/recirculating flap. When the HVAC system is "OFF", the flap should be to recirculate, so no outside air enters. Under normal conditions, the flap should be to fresh air, so ram air can
enter from outside. When the temp is on full cold AND A/C, the flap should be to recirculate, so no very hot outside air is pulled in.
The flap is controlled by a vacuum actuator. If the actuator fails, or if you don't have enough vacuum due to leaks, etc., the failure mode is to fresh air. If the heater valve is also failed, or if there is no vacuum, the failure mode is for heat.
Fix the vacuum system, and the problem will go away.