Just had this learning experience on a 92 400E. The switch actually has a refrigerant line running to it, so that it will turn on low speed when the AC is switched on, and high speed based on the coolant temp. I guess mine is behaving, but wish I could turn it on without the AC, so it would come on low speed without the AC on. I found out from experience that the car will cycle between 107 and 99C in 100F weather at 60 mph, but at 90 mph it stays at 95C! Wish that was a workable solution. Meanwhile, I have probably the evaporator leak on the AC, so can't run the low speed fan. How hard can it be to replace the refrigerant switch with a manual switch?