Originally Posted by tjts1

Any BMW fan switch will fit either in the spare ports in the upper radiator hose neck or in the water pump housing near the thermostat. On my om603 I initially insalled the fan switch in the hose neck then switched to the water pump housing with an 82c switch. This proved to turn on the fan less often and the temp was more stable. I used a temp switch meant for a mid 80s bmw 318i.
The thread size is m14x1.5mm
BMW pn 61311364272
You can find these for 82c 87c, 91x and 103c (I think)


There are also 3 prong BMW fan switches which can trigger low speed and high speed at different temps, 91c and 99c for example
BMW pn 61311378073.


80/88c BMW pn 61318361787K


All 3 of the above will screw right into the spare ports on the Mercedes engine without any modification. Make sure to power the fan through a relay because the switches can't handle the full load of the Volvo fan.

I used a Volvo fan on my 190e and it was a tight fit. Using the stock shroud was impossible. I had to design and build a fan mount from scratch.



Good luck