Coolant temp sensor 1987 300D
 

Had a quick question on 3 pole coolant temp sensor located near the top radiator hose. I power washed the engine and looks like some water got on this sensor, every time I start the car even from cold the aux fan kicks in.
I unplug the sensor the fan goes off.
Question is that my sensor has a RED top and the only ones I see for sale have a blue or green top. Do these units superceed the red top sensor? What are the differences between them?
1987 300D

I deleted the previous post with colors and trip points from memory. Here's info on all but the red switch -

http://www.w124performance.com/image...ch_105-12x.jpg

IIRC the red switch has trip points of 95*C and 105*C. The trip points are etched into the wrench flats of the switch.

Jeremy mentioned that he experienced the aux fan kicking in with the coolant temp gauge around 100*C with a red switch. Then he fitted a new fan clutch and the engine didn't run that hot.

Sixto
87 300D^2

Is this what youare talking about? Auxillary fan switch w133-1630507

http://img.eautopartscatalog.com/liv...1630507BEH.JPG

Charlie

If the first sentence in post #1 is any indication, probably not.

Ok, so the grey switch sounds pretty good. But looks like the red switch has trigger points at 95 wouldnt that make it a better choice? Also I am showing the green switch 0065454524 has superceeded the blue switch.

I missed this line "question on 3 pole coolant temp sensor ". :o

When I read his sensor has a red top, my mind jumped to the sensor I posted.

Charlie

Sixto,

Do you know the thread size of this 006 545 6424 switch? I am doing a feasibility test on eliminating the viscous fan in my 85 300D and need a temp switch to use in the T stat housing to run the electric AC fan as a engine cooling fan.

Good question. I'm without MBs at the moment so I don't have one to measure. FWIW, it's a common temp switch format across OM601/2/3 and M102/3 engines. I'm sure there's a 300E in a scrap yard near you.

Sixto
MB-less

The red switch was never factory installed in a diesel by MB. It shows up in gas-engined cars. Do you need the part #? I have it somewhere.

[edit]

Mercedes-Benz S25/5
Auxiliary fan (high speed) and compressor cut-out switch part numbers are:
• 006 545 64 24 (used in OM603 of '87 300D/TD only) 105ºC/128ºC with blue top
• 006 545 61 24 (used in M102 and OM601 engines plus OM603 of '86/'87 300SDL) 105ºC/120ºC with gray top
• 006 545 45 24 (used in some M103s) 105ºC/115ºC with green top
• 006 545 42 24 (used in M102-3-4 and OM602 engines) 100ºC/110ºC with red top

Don't forget to install a new crush washer if you change switches.

Jeremy

The red switches were used on M102 190E's. I've never understood why Mercedes chose such incredibly high temps for the Diesel cars. The only thing that makes sense is that they were conserving horsepower so the DIN testing looked better.

Funola:

These are 14mm switches. You won't find much selection in that size, especially if you want the double throw functionality. My trick is to remove one of the water gallery plugs on the left side of the head, and replace it with a 22mm fan switch. 22mm switches are used in many VW, Porsche, Jaguar, and Fiat applications. You can find them in setpoints from 72C to 120C. I'm currently using a 95C Porsche switch, and I think the thermal control is as good as it can be. If you wanted to use the electric fans as primary, a set point of 92C, as used in VW's would be perfect. I have access to lots of thermal switch data if you need some help with this.

Also, that isn't the thermostat housing, it's just a coolant outlet.

Thanks for the p/n's . The 006 545 42 24 100ºC/110ºC may be a good choice. Do you know if it's M14 threads?

Please explain what you mean by "Mercedes chose such incredibly high temps for the Diesel cars"? Are you referring to the T-stat temp or the viscous clutch engagement temp?

Did you eliminate the clutch fan and run only the AC electric fan via a 95C temp switch on the head? How does it perform? How often does the fan kick on?

As to whether it's called a thermostat housing or a coolant outlet, how about we call it half a thermostat housing? The thermostat sits halfway in it. The other half sits in the thermostat cover.

Jeremy, I never checked the EPC but memory says Mxfrank is correct about the red top switch being OE on earlier 190E 2.3s.

Mxfrank, the OM602/3 temp switch is 'only' for the aux fan and AC compressor cutoff. Primary cooling is provided by the clutch fan. I don't know the set points of the clutch fan but maybe you know MB spec'd them higher than gasser counterparts.

funola, AFAIK, there is no part of the 601/2/3 thermostat under the turret to which the fan/compressor temp switch and EDS temp sensor attach. All of the thermostat is in the water pump housing at the engine end of the lower radiator hose.

Sixto
MB-less

Yes, but I was referring to the 617.952 housing where I am installing the 602 temp switch.

Ah, yes, that's a thermostat housing :)

Sixto
MB-less