Fan clutch still not coming on...help!

[madhatter]

I had originally had a problem with my fan clutch not coming on at all on my 85 190e and first checked the fan clutch switch to see if it was functioning properly. When the car was warm I jumped the two pin connector that attaches to the sensor and the fan jumps to life, not on the howling mode but on medium speed which is usable. But when I installed the new fan clutch sensor, the fan still did not come on. So, I jumped the two pin connector again and the fans come on again. But strangely, when I took the jumper wires fron the connector and put them on the pins on the sensor still no engagement of the fan. I must be missing something in how this system works or maybe there is a relay that could be causing this problem? If so, please let me know its location so I can check it. Also, I think the odds that the new switch is defective are pretty remote so I am discounting that for now. Thanks in advance.

Steve