Do I have to drain my cooling system to change the fan switches?
 

I have verified that my fan clutch is good by grounding out the lead that goes to the switch at the thermostat. Will I have to drain my coolant to change these switches? I am going to replace the one for the aux electric fan as well.

No,

You don't have to drain the coolant to change the switch on the thermostat housing, though be ready to catch it as it comes out. If your quick about it you should lose only a small amount (half gallon) that you can replace with water. The other switch on top of the engine, doesn't have this problem. The new temp switches don't come with new washers. I would suggest first taking off the temp switch thats on the top of the engine and using it's washer on the new switch for the thermostat housing so when you take the old one off you don't have to play around switching washers while all the coolant leaks out. Take the washer from the old switch you took off the thermostat housing and put it on the other new switch and install it. I think that pretty much covers it.

Chris

Well luckily I believe the one at the tstat is good... So maybe I will just replace the top one.

Your switch at the tstat is probably still good as you've said in a previous posting that the aux fan comes on at 105c. It's getting a different temp reading at the thermostat than at the top of the engine where the gauge sensor is so it could still be in spec. In the later 190D 2.2's (MY '85), the aux fan isn't switched on till 110c anyway. Go ahead and just replace the top 100c temp switch for the fan clutch as you know it's bad. Just screw the old one off and screw the new one in, no draining coolant to worry about.

Chris

awesome! thanks a lot for the help man!