190E engine fan only engages when engine cold
 

I have this problem on my 1992 190E 2.3: the clutch fan is only engaged when the engine is cold. When I start the car, it is engaged. I tried the newspaper test and I cannot stop the fan. However, when I get the engine to operating temp the fan disengages. The temp slowly creeps up and the fan clutch still doesn't lock. When temperatures hit 100C, the electric fan come on.
I tried disconnecting the blue temperature switch on top of the engine and when I do this the electric fan comes on. I guess this switch is the one for the electric fan... Where is the switch for the engine fan located? Why would the fan engage when the engine is cold en disengages when hot?

There is a black three prong temp. switch in front of the two prong temp. switch. The two wire connector on the three prong temp. switch is for the clutch fan.

Cool! Thanks for the info. What is the other wire for? Dash gauge?

Ok look
http://i242.photobucket.com/albums/f...96694457_n.jpg

This is the switch. The single green wire is for the gauge. If I disconnect it, the needle drops to 0. The 2 other wires used to be in a connector I guess, but now they aren't anymore. I got one black/green wire and one black/blue wire, which corresponds to the wiring diagram in the manual. And I guess the switch pictured above is the one circled in red in the diagram below:
http://i242.photobucket.com/albums/f...%20problem.jpg

According to this, if I bridge the black/blue wire to the black/green wire I should power the fan clutch. I tried this, but when I do it the wires spark and the jumper wire get really hot. What am I doing wrong? Do I have the right wires?

Yes, if you short those 2 wires, the fan clutch should engage. When you shorted the 2 wires did the fan clutch operate and the fan engage? Maybe your magnetic clutch is defective if it's drawing too much current. I see your plastic connector is missing. I replaced my broken connectors a few years ago.

When I do oil changes, I like to test my aux. fan switch and clutch fan switch to make they are operating. With the engine running, I put a screwdriver across the connectors and look for the fans to operate.

On another note, I purchased my '93 new and the clutch fan never operated until I replaced the clutch fan temp. switch. Apparently the car came with a defective clutch fan temp. switch.

When I shorted the 2 wires it just made a few sparks and then the jumper wire started becoming very hot. The clutch didn't engage. Could be the clutch, but why would it stay engaged when the engine is cold when I start it in the morning?

Anybody else have input on this?

Maybe a sensor or resistor of some sort. When certain sensors have a certain temperature they may activate to provide a certain current and if there is a break down somewhere you are not getting that current or not reaching the temp because of a fault. Track down the part that is causing the fan to engage when it is cold and remove it. Maybe a relay or something. Then turn the car on and see if the fan is engaged. Let it get to operating temperature and see if it has a default setting to engage it. If not, replace that part and redo the test. Then check the sensors and resistors. Relays are the easiest so I say start there.