installed a new clutch fanand a new temp switch (1 pole) and now both clutch fan and aux fan run all the time. It appears someone has run a jumper wire from the switch on top to the dryier to the temp switch any ideas on why both run all the time?
thanks joel

What year is your car?

__________________
1995 E420 152k
1991 300D 2.5 348116 daily driver
1992 300E 2.6 196k-work in progress(head gasket)
2002 BMW 745Li 93k

Why did you need to install a new switch and clutch fan or fan clutch? What problems were you having with your car? The fan closest to the engine is suppose to spin all of the time, the clutch is in the center and doesn't actually engage until your car reaches normal operating temperatures. The fan is synched with you RPM gauge upto 3000 rpms. If the fan spun faster than that it would fall to pieces. The problem only lies with the auxiliary fan running all of the time. ItVs probaly running at full tilt.

__________________
1995 E420 152k
1991 300D 2.5 348116 daily driver
1992 300E 2.6 196k-work in progress(head gasket)
2002 BMW 745Li 93k

1984 car was overheating in traffic engine fan did not engage--now engages all the time even when first cranked as does aux fan
thanks

How long have you owned the car? Solving the overheating issue is a top priority. Those wires were probably jumped because of the overheating problem that the previous owner didn't want to deal with. There are owners that have never even heard their high speed auxiliary fans come on. A properly functiong cooling system would very rarely allow the engine to get that hot.
Does it still overheat when looking at the temperature gauge? In other words, is the car running at normal operating temperature? This can only be determined by disconnecting the auxiliary fan and taking the car for a drive. If your fan clutch is operating correctly the car shouldn't overheat.

__________________
1995 E420 152k
1991 300D 2.5 348116 daily driver
1992 300E 2.6 196k-work in progress(head gasket)
2002 BMW 745Li 93k

owned car 13 yrs. when I say overheating I don't mean red zone but last week temp began to rise over normal in traffic and the engine fan did not come on . It has never done that before so I replaced the engine clutch fan and the temp switch ( 1 pole) now both fans come on when the car is cranked and run constantly. As I mentioned there is a jumper wire from the switch on top of the drier to the 1 pole switch which isn't correct but would that cause both fans to come on when the engine is started? It has never done that before with that configuration and the engine temp had never risen like that before either

Try to remember that one of the fans are suppose to run constantly(engine fan w/wo clutch engaged. That is not your problem.
The problem is the "OVERHEATING". Yes, a jumped wire from the fan switch to the temperature sensor would cause the auxiliary fan to come on when the car is started which shouldn't be happening. Doing that covers up another issue.
I'm trying to make sure that I understand the situation. 1) Car was overheating
2) Someone bridged/jumped fan switch to temp sensor.
3) You R+R'd fan clutch and temp sensor
4) Now your auxiliary fan runs constantly, but didn't before.
You still haven't told me the order of events. Did someone try to solve your overheating problem for you by bridging the fan? If it has always been wired like this your auxiliary fan should have always been running constantly. The connection point of the bridge may have come loose a long time ago. When you replaced the switch and the jumper it just started working as it should with the wiring. As I stated before the only way to figure out the true OVERHEATING problem is to wire it correctly. With the fan running like that it causes a constant strain on your alternator.

__________________
1995 E420 152k
1991 300D 2.5 348116 daily driver
1992 300E 2.6 196k-work in progress(head gasket)
2002 BMW 745Li 93k

If no one rewire anything before then you can try 2 things:

1) The clutch fan is electrically controlled by a thermostatic ( 1 wire ) switch. I think it is on the left hand side of the engine block when facing the engine. I remember I shorted the wire to chassis and the fan comes on. Try to remove the wire and ohm out the thermostatic contact to chassis. It should be open circuit when engine is cold. It conducts when the engine is hot to turn on the clutch fan. If the wire is removed and the fan still comes on then you have other electrical problem.
2) The aux fan comes on if the pressure switch at the rec/drier is made and A/C is requested by CCU. Remove 1 wire from the pressure switch and see whether the aux fan comes on or not.

Try to do a divide and conquer.

Good luck.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.