They call it a temp sw, but it is actually a pressure sw.

It has a 6" pigtail wire set ..slide the sleeves back on the connectors at the pigtail end and jumper them right there w/key ON ..that will get you LOW aux fan...if NO , relay /fuse / or dropping resitor are bad.

Post what you have with that test.

http://catalog.peachparts.com/ShopByVehicle.epc?q=1989-Mercedes--Benz-4--0sel-Climate--Control&yearid=1989%40%401989&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6265%3AMBC%7C1533%3AED%7C10000055%40%40420SEL&catid=242213%40%40Climate+Control&subcatid=242240@@A%2FC+Temp%2E+Switch&mode=PA

__________________
A Dalton