First time thread, long time reader. I have a 93 300e with 208,000 miles. The only a/c work was replaced expansion valve. On days above 75 F, the a/c will blow hot air from the side vents and cold air from the center vents. It occurs frequently, if I drive over 70 mph. If I stop and turn the engine off for at least 15 minutes, it resets itself and the problem does not occur again until the conditions are the same. On hot summer days, the problem may occur regardless of speed. In the summer, the engine will also run hot when idle with the a/c on. I changed the thermostat, but it did not help. Any suggestion?