My 1990 740 turbo has + 200.000 miles, still drives decently. The airco has never cooled very well though it did cool somehow, better when driving on the highway. Had gas checked last year, just needed to top off. Is there any easy (or difficult way) to tune-up the airco system, other then having it checked on leaks? The compressor seems to come on, I can hear it when idling, I do not know if the heat exchanger looses efficiency over time? Please advise!
