so after just under two months of forgetting about this thread i have remember to come back to it.

to recap, my car was running hot and under the orders of fellow members i jumped the pigtail leads to the low auxiliary fan. that added airflow solved the over heating problem. but as this was just a test, i removed the jumping wire and the overheating problem has returned.

so just today, i was driving home in the streets of san francisco waiting at stop lights and painfully watching the temp gauge rise. where i had a wonderful idea.

check the fans.

so i popped the hood on the side street with the engine running and checked what fans were operating. the electric fan was running on low speed. but the mag cluch fan was not engaged. as said earlier in the thread the fan clutch does work.

when i jumped the pigtail leads again i found this also engaged that mag clutch fan.

my conclusion is that the sensor that activates the magnetic clutch fan is not working. where do i get said sensor.

__________________
Current
2006 E320 CDI, 57K bought at 67K "Liesl"
1986 190E 2.3-16, 198K bought at 56K "Brigitta"
1987 300TD (Chuggin Along), 292K "Friedrich"
1995 E320 Wagon, 200K "Louisa"

Past
1987 300SDL, (sold) 125K, bought for 1$ "Kurt"

Hey guys, I had me 86 190e 2.3 16v for two years now. Just a week ago I'm haveing the same problem here. My temp gauge would go up to about 110c then the (Fan drivin by the belt turns on). Is the the mag fan?

Then I noticed that my electric fan isn't working. (aux fan)?

I powered the fan to the battery and worked.

I also did the pig tail thing n now the fans work like normal.

So what's the part that needed to be r&r?

Thx guys

I aslo replaced the feuses. Number 2 or 3

And is it bad to drive the car with the pig tail jumped for a long period of time?

Anyone?

Max, if your lo aux fan does not engage with the A/C running, but you've powered the aux fan directly from the battery and it runs, you've verified that the fan motor is OK. Jumpering the pigtails verifies that the fuses, the relay (K10), a series resistor (R15) and wiring are also OK. Does your A/C system work correctly? It blows cold? If not, low refrigerant level would explain why the lo aux fan isn't engaging. Charge the A/C system and try again. But if A/C works, then it suggests that the high pressure switch on your A/C drier (the red base component with the 6-inch pigtails) is bad (P/N 004-820-68-10). You should also test to see if the hi aux fan engages as it is supposed to, altho if your main engine fan is working and your lo aux fan is working, it should be very rare that hi aux fan is ever needed.

It is a bad idea to leave the pigtails jumpered. As Arthur pointed out, this is a TEST only. The wiring on the lo fan circuit is undersized for continuous operation.

__________________
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

Ya my a/c isn't blowing any cold air any more. But does the mag fancakways kick in when my cars about to overheat?

Any links on how to charge the a/c?

So what temp does the mag fan usualy turn on at? It only turns on when the car almost overheats. Shouldn't it turn on near the 80-85c?

Hello!
I'm new of this forum, and here (after weeks of research) I finally found a way to solve my problem:

On my 1991 Mercedes-Benz 200E the aux fan don't run in "lo aux fan" mode but the pressure switch works ok and the series resistor it is also ok. What happened?

(the aux fan works ok in "hi aux fan" mode (when controlled by the engine temperature sensor))

where are the fuse and relay K10?

I found a relay in the fuse box, but that's what controls only the function "hi aux fan"!

thanks for your help!

(for Max power: the mag fan of my car turn on near 110°C, but i think 100°C is the correct value)
maybe, if you search for the replacement part, you find out what temperature value works

If the low aux fan doesn't engage, how do you know that the pressure switch and series resistor are OK? Have you jumpered the pigtails on the pressure switch to confirm low fan operation?

Relay K10 is located in the relay box at the back of the main fuse box (position B in the image below). Relay K9 is in position C in the image. The relevant fuses are 7 and D, located in the main fuse box. Fuse 7 is for the coil side of the relay and fuse D is for the load side. At least, this is true for North American versions, I don't have a schematic for Euro versions. Also, you say that you found a relay that controls only the hi aux fan function. If that's so, your car may have two relays for aux fan -- a blue one and a green one (rather than the aluminum cubes shown in the photo), and each relay has its own fuse inside it. Check those fuses.

__________________
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

Thank you for your answer Cal Learner!

The pressure switch is OK because when the A.C. is switched ON, if i put an ohmmeter across the pins, there are few ohms (short circuit). Also across the preresistor i see few ohms (approximately 0,8 ohms)

Thanks also for the explaining image, next week I try to perform the "pigtail test" and try to find the relay K10

Today:

(thanks to your pictures)

found relay K10 (same position and same case color & type of your image)

the relay coil is defective (is open, i see only the value of the resistance in parallel (carbon 470 Ohms 1/2 Watt)

in Italy the original spare part costs 48 euro!

Wednesday I have the spare.

thank you, Cal Learner! You helped me solve a problem that has dragged on for months!

Thanks a bunch guys. I will attempt to use this thread to solve my problem. The pics were excellent, and the procedure was desribed in very good detail.

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

After reading this post hopefully someone maybe able to help me with my problem.
I'm having a similar problem with my 1984 series 1 W201 2.0L.
My Electromagnetic Fan clutch stopped working along with my Tachometer. I have a 3 pole RED temp sensor that has +12v power on terminal 3. If I bridge terminals 3 & 1 the electric fans work. If bridge terminals 3 & 2 the fan clutch doesn't engage. Fuse #10 in the fuse box has power on both ends of the fuse which controls both the Electromagnetic Fan & the Tachometer. See attached photo.
Does anyone have any ideas on what is making both these items not to work or is there a relay not working on this circuit?

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