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S600 MY94 aux fans help.

4K views 38 replies 7 participants last post by  Abbelaio 
#1 ·
Friends 1994 S600, the aux fans do not work for engine temp. The fans work with AC to keep the gas pressure in check, (can see the gas pressure cycling on the CC readout) but they do not work to keep engine temp in check. Engine temp will creep way up in temp and the aux fans do not engage.

He is getting the car on a code reader on the weekend, but I'm sure someone has had this exact same problem before.

Help appreciated.
 
#2 ·
what about two big resistors in grille? i had to replace both of them and it worked.

first, check the contacts of those resistors. they have extermely low impedance (ca 1 ohm i think) ... you can measure and repair them maybe if they are bad.

another idea: temperature sensor responsible for coolant sensing is bad (which i doubt). It is sensor with 4 connectors and it is actually "doubled" sensor for increased reliability.
 
#3 ·
The fans work with AC and if you unplug the middle temp sensor they stay on, I guess that means the resistors are working fine?

Have not played with the two (left/right) ecu temp sensors yet.
 
#4 ·
i am too lazy to study diagram deeply but i can see both resistors are last elements before aux fans, so yes you are right. i thought they are both related to the circuit which controls engine temperature only.

logically the N22 = control unit in the cabin can be damaged.
 
#5 · (Edited)
Samo ,This S600 in question here ( Ilhan's) doesn't have the two Resistors in-between the fans (my 600 has them) ,all there is - is a small black box in the middle of it .
I opened it up & found a lot of corrosion on the circuit board inside , unfortunately it wasn't the problem . We changed all Relays including the once under the Fuse box & swapped the Relay near the Headlight out ( if you don't know there is a Relay hidden next to the Headlight ) , even that dosnt activate the Aux fans .
The only way to activate them but then don't turn of anymore unless the engine stops is when you bridge the Temp sensors terminals .
ATM Ilhan is scanning the car but I do it again in the morning with our scanner (Jimmy's) , that scans the 140's really good ,takes about 30 minutes plus to do a complete scan ,everything activates by itself on the car doing this , I don't think that the mechanic Ilhan has the car now , is using a scanner that is adaptable for W140's .
I still have a suspicion on the relay near the headlights or booth the AUX fans are defective somehow ,they are way to noisy when they do come on , I can barely hear mine on my car when they come on even that they do sound like as if a Jumbo jet landed behind me ,lol (only slightly kidding ) .:thumbsup:
 
#6 ·
I really think that black box thing is not factory. I told him to get live data off the ECU coolant temp sensors to see if any are faulty, and return the system to factory spec.
 
#8 · (Edited)
Black box (or resistor pack) should be to control the fan speed only.
Not familiar with the electrical diagram, but it usually is pretty simple -- temperature sensor closes, energizes the relay and power goes to the fan.

If the fans are working with the A/C but not when the engine temperature exceeds certain point, the culprit should be fairly easy to find by tracing the continuity.

Out of curiosity, do the pusher fans operate at different speeds on A/C and engine over-temperature?

Good luck,
Steve
 
#7 ·
but anyway, HVAC control unit can also be a cause, is that right? can you check if it gives any output? for my car it seems that pins no 5, 14 and 4 (connector no 1, so left one i assume) give minus for aux fans for stages 1, 2 and 3, respectively. so it seems that plus terminal is constantly on, and HVAC control unit controls minus terminal. This is actually beginning where you should start.
 
#9 ·
Joe,

We are having the SAME problem here, but for the moment it is a secondary fix....

My seat buddy Craig just went through all of this. I went to go help him on his 95 S600 Coupe. Those fans on his car kick-on near the RED-LINE temperature which is silly.

Now the underlining problem on Craig's S600 is the stupid fan clutch, and $690 for the OEM clutch fan is ridiculous, so for the moment he using the clutch fan from his 500SEL.

I was helping him yesterday, and maybe you are have clutch fan problems like Craig.

Well, a fix for the EXPENSIVE fan....

http://www.benzworld.org/forums/w163-m-class/1583106-ml-320-fan-clutch-repair.html

http://www.benzworld.org/forums/r129-sl-class/1671922-fan-clutch-refill-diy.html

Viscous clutch/fan repair - PeachParts Mercedes ShopForum

Viscous Fan/Clutch - PeachParts Mercedes ShopForum

Here in the USA. I too would not fork-out $690 for the fan clutch, so I would use another brand fan. Like this Toyota one that can be fixed...



Martin
 
#11 · (Edited)
Now the underlining problem on Craig's S600 is the stupid fan clutch, and $690 for the OEM clutch fan is ridiculous, so for the moment he using the clutch fan from his 500SEL.

I was helping him yesterday, and maybe you are have clutch fan problems like Craig.

Well, a fix for the EXPENSIVE fan....

http://www.benzworld.org/forums/w163-m-class/1583106-ml-320-fan-clutch-repair.html

http://www.benzworld.org/forums/r129-sl-class/1671922-fan-clutch-refill-diy.html

Viscous clutch/fan repair - PeachParts Mercedes ShopForum

Viscous Fan/Clutch - PeachParts Mercedes ShopForum

Here in the USA. I too would not fork-out $690 for the fan clutch, so I would use another brand fan. Like this Toyota one that can be fixed...

https://www.youtube.com/watch?v=zjhKr5usjaA

Martin
Before I do any of those fixes, I'd look on ebay:

RADIATOR CLUTCH FAN FOR MERCEDES BENZ 500SL 400SE 500SEL 600SEL 90-02 REPM313707 | eBay

It is going to be PRC-made for sure, but even if it lasts one year, it is only $50 shipped to your door.
Plus, replacing the fan clutch is a 20 min job on the M120.

I think I read somewhere that the pusher fans on this engine will operate at full speed when coolant temperature reaches/exceeds 102°C.

The mechanical fan should be moving enough air through the radiator to keep the beast cool (provided all other components are up to sniff)

Steve
 
#10 ·
If the fans are working with the A/C but not when the engine temperature exceeds certain point, the culprit should be fairly easy to find by tracing the continuity.
i agree.

it is logical to me that different elements (or chips, or whatever) on the circuit board are responsible to bridge minus terminal which goes into aux fan relay module. so for AC fans can work ok, and at same time they will not react on coolant temperature changes. I still think you must find a proper diagram for your car and see it corresponding outputs from N22 unit do their job.
 
#13 · (Edited)
Roles reversed on this one...

Fan clutch and radiator for my wife's Audi -- 1/10 of the dealer price -- definitely PRC made. Going strong 4 years and counting .... :))

I gambled $100 and lucked out. You didn't.

But then...on a different project I gambled close to $10K in parts, mostly dealer and high-end aftermarkets and lost big time (that little fella that seals the output shaft at the final drive was a brand-sparkling-new seal in a MB bag).

Do we call this a zero-sum game?

:)

Steve
 
#16 ·
URO fan clutches are garbage, lasted only a couple of months each for me before I bought a Sachs. Though, they were easy and quick to change for me with no special tools (small hands are quite the genetic gift for car people).

As for the auxiliary fans not working....I gave up on mine eventually and put them on a toggle switch.
 
#17 ·
Found over 70 maybe 80 or more error codes on Ilhans S600 , looks like this car has never ever had a scan .
Ilhans Mechanic only found 1 error code which was for the Window Regulator ,is there even a code for them ?.
I told Ilhan to meet me & all those codes came up , I cleared them all several times to make sure , except for these two in the picture below ,they are for the AUX fans , every time I rescan that section TAU/KLA/AAC the fans activate then stop , then I get the code again .
We tried the new fans that Joe delivered super fast on request ( Thanks Joe for the quick Service btw ,not even UPS could have done that quicker ) but they also don't activate .
Tomorrow we going to take all the sensors of my spare V12 engine ,I suspect it could be a NEW faulty temp switch or that the Fan Clutch has something to do with it as I don't hear the Click sound when it engages like it does on mine .
We might consider to swap the center black box in-between the AUX fans to a Resistor one like I have on mine ,maybe that will do the trick, I don't like the look of that box or whats inside it .
Ilhan is extremely upset about this .:thumbsup:
 

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#19 · (Edited)
These are the only codes I cant erase ,they are in the Fan section for scanning ,nothing else comes up .
I got the 006 code erased leaves the 074/075 .I don't know if they even have anything to do with the fans at all.
BTW : At one Stage I did get the fans to turn on ,at Temperature around 90ish ,all on there own but that was only once .:thumbsup:
 
#20 ·
oh i see. sorry my car has OBDI strategy. that one is OBDII ... i have no experiences.

i would check if HVAC control unit in the cabin gives any output on the corresponding pins. I still think that under given circumstances this is only right way to solve the problem. just find right pins in diagram.
 
#21 ·
I don't think it's OBD 2 as it has all the same like my car .
Don't look at the scanning device ,that's just a real good scanner that does everything .
Even Ilhan was amazed as I scanned the car when all the gadgets etc turned on all by them self's for testing ,heater -aux fans- Ac-blower etc ,all turn on one at a time ,I don't think that the Blinking gadjet that is used for early 140's does that , if I had to use that device ,it would have taken at least two days or more to scan his car ,not mentioning getting confused while counting the blinks ,(6-7 - 34-37 etc ,whoops where was i 22 or 23 ?,lol) ,with so many interruptions ,it would be impossible to keep track counting .:thumbsup:
 
#22 · (Edited)
oh i see. sorry my car has OBDI strategy. that one is OBDII ... i have no experiences.
of course it is not OBDII. Everybody knows OBDII started in 1996. Oh that samosali, it seems he sometimes drinks too much tea.

so to apologize myself ... this is when one is active on more posts here and concentration decreases. The border between OBDI and IBDII was one of the first things I have learned when i purchased my car ... but too much tea evidently is not good for me.

nevertheless i still think control unit is a highly possible culprit. the tea does not affect ideas.
 
#23 ·
LoL Samo , Don't worry it's all good , You know that with me you can even say that it was OBD3 or 4 , I get the message just the same .
Enjoy a bottle or two of what ever you drink & have one extra one for me while you at it ( I don't drink alcohol unfortunately or fortunately,lol) .
I think i'm going to soldier a Resistor in-between the temp sensor ,1100ohm or 512 ohm ,see what works best on his car , I don't like to see one of my best friends unhappy . The Rain has stopped us yesterday from taking anything of my spare V12 engine ,so next weekend .:thumbsup:
 
#24 ·
Ok, let's forget beers and vine for a moment ... :)

So you have intention to increase resistance which is typical for the built-in engine coolant sensor which of course is dependent on the coolant temperature? or to decrease it? it depends on how will you mount the additional resistor. In line or in parallel? if you will mount it in line you will increase resistance. mounted in parallel it will decrease common resistance. Next, higher resistance means lower engine coolant temperature for computers in the car.

So I guess you want to check first if the system works in general. This is not a bad idea. So in my mind you should mount the additional resistor in parallel. I do not know how many Ohm resistor but if you think i am thinking like you we can discuss it.

I guess the two-poles temperature resistor in the engine is the one which has to be modified temporarily, is that right? it is responsible for HVAC and aux fans if i recall correctly, but i can check ... you can check in the diagrams. i am pretty sure that the four-poles sensor provides data only to engine brain (fuel, spark)
 
#31 · (Edited)
93-95 have a two-stage fan, and from reading the diagnostic data. The low stage is activated on the low air volume on the AC, and the high stage is operated on high fan setting in AC mode.

Pin 4 is putting out less than one volt on connector 1 for the low stage fan

Pin 14 is putting is putting out MORE than one volt on connector 1 for High stage fan...

These stage settings are driving the K9 relay, so monitoring the volt levels from pin 4 and 14 one can emulate the fans, but i do not have one of these old cars. I do not have the exact voltages, so here is the info..

Martin
 

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#33 ·
Ok, Today I changed out every single relay and Sensors on Ilhan's engine , I used all parts from my own 100% working 600 , Aux fans never turned on , the only part (resistor ) I cant change as it's different is the resistor in between the two aux fans , I don't like the look of that black box with the ciquit board inside it ,completely corroded ,ilhan is trying to modify it now with the same I have on mine , just simple resistors .
Lets see .... .:thumbsup:
 
#34 ·
but Chris, Martin told you which pins on control unit give juice for the fans (see his answer above). why don't you check it? once you have access to the unit is it 10 minutes job. another 15 minutes to get access to then unit.
 
#35 ·
I haven't read them yet as i'm to busy , just saw them now . I will tell Ilhan to get a good read . He did mention to me that if the fans don't get the correct voltage that they don't power on , this was after I changed all the parts lol.
At least we can rule out all relays and sensors now , makes it much easier to diagnose the next steps ,just like diagnosing a faulty PC computer ,eventually I hit the right spot .
Ilhan is very lucky to have me on his side since we have the same cars so parts exchange is no problem & he doesn't need the Mercedes dealers crap,they would do the same thing anyway ,guessing which part could be faulty at an extraordinary cost and in the end it still wouldn't be fixed .
I will take the headlight out and check the pins on the junction relay behind it .
At the moment i'm putting my own car back together after todays adventure with Ilhan,lol.:thumbsup:

BTW: Thanks Martin to post those PDF's , I check them out later .Hopefully an easy solution lays within.... .
 
#37 ·
They only turn on (staying on constantly) when one pin on the temp sensor is either removed or bridged in-between , thye only stop when the engine is of then.
That's how Ilhan is driving the car for now , I could hear him arrive 100's of meters away ,sounds like a Jet is about to land ,lol.
Since I changed the radiator his high temps are all the way down to around 80/82 ,that's with AC on / AUX fans on .:thumbsup:
 
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