this is my 3rd.. sdl that i have..... everytime i bought the cars, i tried washing the engine... after im done.. the engine looks spotless , but the fan remains on at all times after turning on the key.... now.... i dont think its that sensor, thats on top of the thermostat housing... because on my other ones i changed that but the fan would not come on at all... any ideas or experiences?? thanks..
also.. if i take out the wires out of that sensor ,, the fan shuts off... but why would a sensor always go bad when washed.. do you think because it was hot and when it gets sprayed with cold water it just breaks..?? or some kind of electrical issues? man this s**t go me thinking..

The a/c receiver/dryer has a switch that also starts this fan. If it has shorted, the fan will run all the time. Try unplugging one wire from the r/d switch.

On my old 603 this switch was broken, and it did not start the fan even when needed. In hot weather, I jumpered it and let the fan run,

Somewhere on this forum we were advised to keep the switch on top of the thermostat dry when washing the engine. I have always covered mine with a plastic bag and had no trouble.

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DS
2010 CL550 - Heaven help me but it's beautiful
87 300D a labor of love
11 GLK 350 So far, so good
08 E350 4matic, Love it.
99 E320 too rusted, sold
87 260E Donated to Newgate School
www.Newgateschool.org - check it out.
12 Ford Escape, sold, forgotten
87 300D, sold, what a mistake
06 Passat 2.0T, PITA, sold

Las Vegas NV

gsxr had the same problem happen to him. It is the switch I believe.

Thanks
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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bet you its the three terminal switch! I bought a spare last time I had to order one. Oh, did I say I have two 603 engines to feed? Ah yes!
Its probably that switch like I said. They don't like moisture.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

is it the switch on the thermostat? the 3 pin. when changing that... the problem goes away but the fan doesnt come on when its suppose to...

Wait a minute,

I'm confused, I thought the switch controlling the aux fan was ontop of the engine, right near the intake runner for the #1 cylender. My thermostat is on the right side of the engine right near the turbo; I don't recall any switches being too close to it.

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1987 300TDT (294,000 km)

Your engine is just trying to dry itself off with the aux fan...would YOU want to be all wet after taking a shower like that?

I think not

Maybe your engine is different, a 603.XX?
FWIW gsxr recommended using a later model thermo sw, it closes at a lower temp. The insulation is grey instead of the turquoise blue the original switches are. here's a pic of mine, near water neck, top of head, L side.

Attached Thumbnails

 

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

gsxr said:
"Two things trigger the electrical auxiliary fan on 1986/87 diesels. First, there is a pressure switch screw into the A/C receiver/drier. The old type is green, the new type is red. Short the two leads together and the fan will turn on LOW speed. If you have the green switch the fan may not run often with the A/C on, the red switch fixed this.

The second trigger is the 3-prong switch on the water neck at the top of the cylinder head. The 2 terminals are the fan trigger, they will close at approx. 105C and turn the fan on HIGH speed. Short these together and the fan will turn on. (The 3rd prong is the high temp safety that kills the A/C compressor when the temps go above 120C or 128C, depending on which switch you have - just ignore this terminal.)

The actual cube relay is located in the rear half of the fuse box, the section you have to remove screws to access.
Dave Meimann"

DDH

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!