1985,500sel, 112,000 miles. When car is normal operating temp, leave sit for 15 mins. With A/C on from a dead stop car will run like turning key on & off rapidly. Turn off a/c car immediately runs fine. Will not always happen somedays car is fine.I found that by unpluging aux fan the problem is cured.I even built a new wiring harness that connects all the underhood a/c components(compressor, temp switch, pressure switch and fan and grounds.I replaced the fan motor armature as a last resort. Current draw on start up and run on the aux fan are well within range. Remember EVERTHING on this car works as it should.I only use genuine Merc. Parts.I am a A.S.E. Cerified master mechanic.