Hi to everibody.
After search a lot on web and on '' search'' i need your help.
I have w 124 300 D turbo eurpean 1992.
I am triing to solve some hot running problem and investigating abour switch on temperature for auxiliary fan.
As i understiid my car has 3 temperature sender:

-B 11/4 1 wire it is Ok and used just for ELR

- BLUE sender on top of cooling neck 2 wire this is NTC i think for high speed auxiliary fan but i can not understand at with temeprature must switch on.

- GREEN sender on middle of head 2 wire as i tested also NTC one is for temperature gauge and second i think for pre geting relay.


I founded on internet one RED 2 wire swith 95C-100C to swtch on auxiliary fan but it is not NTC so i do not know if it is safe or not install this.
Car has new T-stat, fan cluch,water pump, auxiliary fan work at low speed but i would like to be safe with high speed also as i changed my craked head already once and i really not want see gauge more than 100 or 105 C max.
Thanks a lot to all can help me.
Alberto

BlUE SENSOR is 0085424517 on intenet is wrote 130 C
but i can cleary read on sender 92/105.
really confused
Alberto

What kind of condition is the radiator in? Have you done a flush of the cooling system? If the water pump and engine driven fan are operational, that should be more than adequate to keep the system cool. The Aux fan is there for A/C operation and as an emergency backup if the engine driven fan can't keep up with cooling.

The temp switch that controls the Aux fan operation is the 2-pin switch on the coolant neck on the front top part of the engine.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Hi Thanks a lot
Yes radiator is clean and i flush it, also coolant is new.
As i live in region with mountains, also traffic jams, and in summer temperature outside can be 37 C.
My temperature go at 100C or a little bit more when i stop for traffic on mountanis.
I can feel aux fan running al low speed but i would like to know kick on at high speed.
I tested circuit is ok if i bridge the blue connector on cooling neck aux fan run at high speed.
Thanks a lot
Alberto

http://www.peachparts.com/shopforum/diesel-discussion/132969-dead-temp-gauge-87-300sdl.html

check with post #8.

It is normal for the engine to run between 100C to 110C in mountainous area or climbing.. I would not be too concern. The sensor that controls the AUX fan is 3 prongs. The aux fan runs at slow speed when A/C is on and high pressure switch is made at the receiver/drier. It runs at high speed when coolant is at high temperature trigger, depending on the color of your 3 prong thermostat. Link below. Hope this help.

http://www.peachparts.com/shopforum/diesel-discussion/158031-603-aux-fan-switch.html

see post #2.

__________________
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.

I don't have a FSM or wiring diagram for the 124, but on the 126, low speed is only activated by the A/C system. The high speed is triggered off the temp sensor in the head and closes at coolant temps >105˚

If you aren't getting to the trip point of the cooling fan coming on due to coolant temperature, it won't trigger into high speed.

As a sidenote, if the coolant temperature isn't getting high enough to trip the aux cooling fan into high speed, your engine isn't overheating. Temps between 80-100˚ are considered normal, even if they move around as you drive.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Looks like Ah-Kay is a quicker typer than I am!

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Thanks a lot
But my car is not equipped with 3 prongs sensor i would be bettre but i have:
1 single wire sensors
2 double wire sensors
i will post pictures

http://www.peachparts.com/shopforum/attachment.php?attachmentid=142389&stc=1&d=1495734323

Attached Thumbnails

 

The 3 prongs sensor is similar as 2 prongs. It probably is missing the 1 prong to cut of the A/C completely.

2 prongs - activate the AUX fan at high speed

3 prongs - activate the AUX fan at high speed, 1 prong to kill the A/C ( fed into the Kilma relay ) or something, I cannot remember.

__________________
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.

1st is for ELR
2nd is for auxiliary fan but is NTC sender.
3rd is for pre heating and temperature gauge i think

You can do some tests if you have an ohmmeter.

1) The left hand most one is temperature sensor for the dash gauge - It is a resistive sensor. The resistance varies with temperature, dip it in hot mater and check the resistance before and in hot water.
2) The right hand most is probably for aux fan, high speed. - It should be open circuit. Dip it in boiling hot water and it should close if it is rated 100C.
3) Middle one not sure - it should also be a on/off sensor. check it with a ohmmeter.

You can do some other test.

1) Disconnect the dash gauge sensor and the temperature should show 0C.
2) Short the connector plug going into the sensor at the top of the radiator hose and the aux fan should come on at high speed.
3) Short the connector plug at the rec/drier and the aux fan should run in slow speed.

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.

Hi Ah Kay
tested 1 st sensor Ok got 5 Volt on wire and this is for ELR idling.
2nd blue sensor he is also NTC but if i bridge 2 wire aux fan come on at HIGH yes.
3 rd green if i disconnect no temperature to dash and i think the other is to kill A/c if too hot.
But i fouded my problem after investigation....i have the wrong T-stat my start open at 85 C.
For my region i think it is bettre 80 C but exist also T sta open at 71 C for very hot clima.
I think i wil change soon before summer my T stat again as this one 80 C i this is completely open at 95 C it will be perfect.
Thanks a lot
Alberto

If a car never looses coolant. I would check the actual temperatures with a thermal scan reader first. The older the car the increased chances that some component is aging. Or that for your model what you see is normal.

In your case for example the temperature gauge may be reading a little higher than the reality. As the sensor might be off calibration. Not likely but I would want to know.

The poster that mentioned you may just not be reaching high enough temperatures. To reach the designed turn on point for the high speed electric fan is a reasonable thing to check.

That thermal switch could be good or bad. I would test it when the wife was not home. By putting it into the oven with an accurate temperature gauge viewable through the glass front panel. To see what temperature it closes at. The small wires will not deform the oven seal.

I am not smart enough to know when a radiator is failing either. The only absolute test is to sub in a new one. They loose efficiency with use over the years . I also believe you have a fluid coupled fan. Test it as much as you can. Some also lose fluid over the years but can be topped up again.

Actually suspected engine cooling systems issues can be a pain it the ass. Or if funds are low. You can buy a thermal switch for appliances for a dollar or two delivered from China on ebay.

So the high speed fan comes on at a temperature selected by you. They come in enough temperature ratings to meet a lot of purposes. You figure out a way to mount one but it does not have to be in liquid. I might for example try one with a closing value of 180 degrees surface mounted on the head. Just wiring it in parallel with the existing switch if it tests good.


You indeed may have found your issue. I just read your last post. I always test older and new thermostats in a pot of water. Unless one has obviously totally failed. There have been far too many issues otherwise over the last few years with the new ones. Unless in your case where the temperature gauge read the same with both the old and new thermostat. If it did chances are strong both thermostats are good.