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.