I have a 1991 560SEL with 68,000 miles. Great car- had it since new. The
quality surpasses the new ones I think.
Today I noticed that on a long bridge going up the AC recirculate door
closed ( stopped recirculating ).
This would suggest a vacuum leak or weak vacuum motor or bad hose. Does
this car have a vacuum reservoir or some sort of check valve system for
the AC system.