First of all why did you change the fan? They very rarely go wrong. History of the problem does help with diagnostics.

 

I see thank for taking the time to type that. In the case of a fan going bad in this the effect it will have on the small electric motor that drives it. The motor may have burnt out.

Disconnect the motor and with the engine hot test for a feed on the motor cable. If the feed is there then the motor is bad.

 

Well, after some discussion with a tech at the dealer today I got a usable wiring diagram printed up. Come to find out there is a relay but the fuse diagram that comes with the car did not have it labeled correctly which lead to my initial confusion. The WIS I have on my computer also did not help me much and even at the dealer their updated WIS was a PIA to sort through.

I have ruled out the relay, the low current signal that triggers the relay, and the high current signal controlled by the relay. I then traced the wiring from the 60 amp fuse to a remotely mounted fan control just above the Airmatic pump behind the front bumper. It appears that +12V reaches the control from the fuse box but no power leaves it to the fan. With the control unplugged I also no longer get any fan malfunction error.

I am thinking that the fan seized up, leaving the motor still drawing current and over loading the control. I opened up the control to find no sings of overheating or any visually burnt components. Even so I am 90% sure by the the trouble shooting that the control is the problem. It is just a shame that a seized up fan took out the control.

 

^The cause and effect may actually be the other way around ie a bad control unit made your fan run at high speed for too long and hence the broken fan is the result and the control is the cause.

 

That could be very true. I just assumed since the fan had been making noise that it was the initial cause and not the result from something else.

 

I thought I should update this for anyone in the future with a similar problem. I ordered a new fan control and now the car is back to normal.

The control was OEM and even in a MB box. I got it from KO Performance for $208

I found a BEHR (OEM manufacture) fan for $569 from DriveWire.com

I also installed a new relay which was $10 from the MB dealer.

This was one very expensive radiator fan fix but it was really really easy to change the parts.

 

I recentley had the same problem but no overheating. My bearing went bad in my fan and you can not just change the bearings you need to buy a whole new assembley. Same with the pulley on the dam thing. Anyways long story should I bought a fan shroud from a wrecking yard for $275 and bam its like brand new. I have a extra fan motor now if you need that I can sell for cheap. Anyways even after you put in your new shroud make sure your coolant, antifreeze/water levels are good because alot can leak when you remove your broke one. I changed mine and the car runs still the same between 80-95C (Very good considering I have 210700 miles).

 

Radiator fan relay

I have a similar problem with the same coolant temp message with my 2000 S500.

While driving, I got the error message but the temp showed still under 120 deg C and I do not know whether the fan was working or not. When I tested it at home, the rad fan was not working at 85 deg C.

Fan can be rotated easily by hand but not working by itself. Fuses 33 and 48 are OK.

Could you please inform me which relay, K, L. M, N, or O is for the radiator fan? How did you test the relay?

Where is the fan control system located? Is it at the same place as the fan motor housing?

Could the fan motor only be removed by unscrewing 3 bolts?

Thanks.

 

Open the hood next time before you turn off the engine and run your AC after a trip from the house. Visual check if the fan is running. If you have 85C your cooling is fine. You may just need some coolant. What message you got ? Coolant low ? Temp Hi ? or both.
Please complete your location profile so we can guess where are you in this world. That will help us Chung, I am chinese too.

 

Radiator fan is not working

Coolant level is right above the bottom of the black top portion of the resrvior. Coolant temp msg with "visit shop" was the only error I received. When I tested it at idle, the msg showed again although temp was between 80 and 90C. It resets when R button is pressed. This problem originally occurred after a heavy use of air-conditioning.

An unusual high pitch noise, which is of wax and wane nature is produced while the engine is running ever since I noticed this coolant temp message. In my non-expert opinion, it sounds like some kind of compensatory variable speed control mechanism, which is trying to feedback to the fan motor.

At this time, my differential diagnoses include fan relay, fan control system, fan motor, and fan belt(if such a thing exists behind the fan assembly and motor). That was why I asked how to locate and check each of them.

I am a native of PA and live in rural Soutwestern MS, USA. I am retired and tried to work on this myself mainly because the dealer is 2 hours away from here. Any advice would be greatly appreciated.

 

Hey Dr. J,

The radiator fan motor is going out. It's sold as a new assembly; fan, belt, shroud and all. Coolant will spill, so make sure you have extra.
The wail should sound like a jet engine. It's a fairly easy DIY as there are only 4 bolts that hold it in place and a connector plug. The only issue is that you have to move some hoses out of the way and there's no way to get around the coolant hoses without spilling a bunch of coolant.

If you're looking for a cheap and good fan, I bought this one. It also has my review on it at Amazon.

I hear legends of people being able to get the motor out and changing the bearings on it for >$50, but never really saw a write up.

I'm planning on writing a page on disassembling the fan motor (I kept the old one) and replacing the bearings, but my sister's birthday is this weekend and she might get upset if my present for her are dirty hands and old Mercedes fan motors.

My advice is to leave the car be until your part arrives, but if you must drive, clean your radiator as well as you can, and though loud, the fan should still be able to cool the engine. If you haven't changed the fluid, now is a good time as well.

Good luck Dr. J

 

Diagnosing radiator fan motor and belt

Dear Gabby07621,
Thank you so much for your prompt advice.

I'd like to confirm that the fan motor is out of order and the only cause. I assume that I can unplug the feed cable from the motor after removing the outer plastic casing and check the voltage and current at the cable terminals. Is it correct?

The fan motor did not seem to have any revolution when I examined during an idle test. I wonder where the wailing noise was coming from.

Could I replace the fan motor only by removing 4 bolts which attach it to the fan/shroud assembly?

Thanks again.

 

Chung
Is the noise is coming from the fan motor area ? I can feel the fan blade is not directly attached to a motor because it can move freely without the motor on, but with some resistence. I think there is a clutch between the electric motor and the blade. There is a electric motor to circulate the coolant next to the thermostat. It may be the source of the high pitch noise. The pump may operate at high speed to compensate for cooling the engine. Use your mechanic's stethoscope to locate the wane. I did a test in my car here is what it should do. Once you have your AC on, the fan should start running. The blade is connected by a belt from an electric motor, the belt is connected to a clutch at the center of the blade. If you can disconnect the motor from the belt, you can check the operation of the motor by a helper to turn on the AC to see if the motor is good. From there you can decide which direction you should look for the faulty problem

 

Radiator Fan motor replacement

Thanks to all.
By the way, can anyone tell me if the radiator fan motor could be detached from the fan/shroud assembly? If so, how(removing 4 bolts)? Is there anything to be difficult or careful about while separating the motor from the assembly - such as fan belt undoing from behind?

Can I assume that a fan motor itself is available to purchase?

 

In order to make a definitive diagnosis, I am trying to unplug the source electric wires from the fan motor.
Can anyone advise how to do it?
What are expected when the voltage and amps are measured if the source is good?

Talking to a service adviser at a Mercedes dealer, he said he was unsure about the wailing noise. He did not think that the noise was caused by the fan/motor assembly malfunction.
Is the wailing noise we talked about before supposed to be coming from the fan motor or another compensating mechanism?

Thanks.

 

I would bet that you are having nearly the same problems I had. The "coolant visit workshop" is a specific fan control error. Regardless of engine temp when the a/c is turned on the fan is turned on, so if it is not working properly you will get the error message. I bet if you unplug the fan control you will not get the error message and as for the noise I bet your fan motor is on the way out. The fan and motor are not serviceable period, I tried on my bad unit that I removed.

To access the fan control, raise the car with the airmatic or raise (with a jack) the front passenger's side, remove the splash shields under the front, pop out the plastic grill on the right side of the bumper, and remove the horn. The gray box approximately the size of a deck of cards (but thicker) is the fan control. Unplug the connector and then crank the car with the a/c on. If you no longer receive the coolant error, you have found one of your problems.

 

A few more questions

Thank you for your reply.

Could the "coolant visit workshop" error happen when one of the fan, belt, clutch, or motor is malfunctioning without the bad fan control?

From the fan control, does the fan motor get the main electric power or only the (secondary) control signal?

Is the fan motor the only mechanism that turns the fan blades or does the fan receive another signal for variable speed or clutch control?

To reduce the amount of work and cost, I am trying to figure out a logical sequence of exmanination and replacement if there is a possibility of only one bad part/system.

Thanks again.

 

Could the "coolant visit workshop" error happen when one of the fan, belt, clutch, or motor is malfunctioning without the bad fan control?

Please stop breaking the fan into the motor, belt or fan, it IS NOT serviceable, it's all or nothing. Yes, the belt could have broken but that is probably 1 in 100000. The fan or control could be causing the error but without the MB software, there is no way for the home mechanic to know directly.

From the fan control, does the fan motor get the main electric power or only the (secondary) control signal?

Is the fan motor the only mechanism that turns the fan blades or does the fan receive another signal for variable speed or clutch control?

Power from the 60 amp fuse and relay runs directly into the control (inline, before the fan) and the control directly regulates power output to the fan for variable speed by other inputs that go into the control.

It could be the input signals to the control, the control, or the fan. However, I would think that the signals to the control are working since the error recognizes that the fan is not working when it should be. So check the obvious, try to turn the fan by hand as it should be easy and smooth. Then make sure that when the fan should come on, power is supplied to the relay and 60 amp fuse. After that there is nothing you can trouble shoot without MB software. You can try to disconnect the fan's connector in an attempt to see if it is receiving power with a multimeter, but the computer might automatically turn the circuit off and you will not read anything which could make you falsely assume the control is bad. On the up side, if you do read a power signal and when reconnected the fan doesn't turn, you'll know the fan is bad.

I would recommend having some software hooked to the car OR order a new control and if it doesn't work order a new fan.

 

I'm traveling right now but when I get home, I'll put up the Mercedes way to replace the fan. I can tell you now that it is more involved than just removing some bolts and plugging up some hoses so that coolant doesn't all leak out. In fact I remember distinctly that you have to drain it out using the drain valve at the bottom of the radiator.

As much as I read directions, I tend to ignore them just as often. That is my right and I will exercise it! =)

 

Fan belt missing

Thank you for your reply.

Examining further the inside of the shroud, I found the fan belt was not there. Probably broken and missing. The clutch felt OK since the pulley engaged and unengaged at different times and turned smoothly when rotated manually. I also felt the motor working. It seems that the noise described before was produced when the motor was turning much faster, which I think was a compensatory control. The dashboard error msg came several minutes after A/C was turned on.

Hence I am pretty sure that the fan belt was the culprit. Now, I wonder if there is a way to replace the fan belt only. If the entire fan/motor assembly would have to be replaced, I would like your advice how to do it including how & where to unplug the electrical connection(s).

I would greatly appreciate it. My S500 has about 55K miles on it.

 

Broken Fan belt

Finally I detected and pulled out the broken fan belt. It was one piece although two ribs were separated & severed and the lateral cord is still holding the belt into one piece. From this finding, I would say that a new replacement fan belt should go in but an access from the back between the fan blades seems unfeasible. I wonder if the entire fan/motor/shroud assembly should be loosened to gain the front access.

In this string of the forum, I saw at least two folks replaced the fan assembly. Would some of you tell whether the fan belt could be mounted from the front access?

I located the replacement fan belt at the following site (the 2nd item on the web page). I am hoping this is the correct part.
00 2000 Mercedes S500 Multi Rib Belt - Drive Belts - ContiTech, Dayco - PartsGeek

As you mentioned, if the fan/motor/belt assembly is not serviceable, I would have to replace the whole thing with your help with the instructions.

Thanks so much.

 

Wow all that for you to see that it was just the belt?!!
The belt can be replaced without removing the whole assembly, but you have to take the cover off of the fan motor and loosen the bolts holding it in. Carefully wrap the belt around the fan end, then onto the motor shaft (while motor is unscrewed) Once both ends are on the pulleys re-install motor bolts. I guess we now know that whining sound was the motor turning at mach 4 without a belt on it..

 

Belt mounted and all appear fixed

Hello, all.
The fan belt was mounted after making some room to access to the fan and motor pulleys by removing the fan shroud bolts(there are only 2 bolts on the top and the bottom sits on the slit without bolts) but still leaving it in place. I did not have to loosen the motor bolts since I put the belt on the motor pully while turning the belt on the fan pulley. It was tight but I managed to slip it on.

(One fan shroud bolt broke off so I would need to fix it. I probably drill the fan housing and tie it to the front somehow.)

No noise or error message on the dash so far. All seem to work OK.
Thanks to everyone for your tips.

 

fan control unit?

2000, S500 - 3 years ago my fan was making screeching noise. Not wanting to spend $1200 at the dealer I decided to fix it myself. Think Safety!
To prove that it was the motor – with the car off I connected 12v directly to the motor – screech. I then removed the belt – screech. Yep the motor. I took the motor apart to see about replacing the bearings. I could only replace 1. The other was fixed. I attempted to purchase just a motor, no luck. Had to buy a complete shroud, fan, and motor assembly ($300). I took that motor off the new unit and tested it. Worked fine – quiet. Installed just the motor. This solved the screeching noise problem, but the fan was not running all the time. The car would still heat up to 100+. So, the fan control unit was not working correctly? I don’t remember the exact test, but I check the voltage input (12V) and output The output was not what you would expect. Input was good, but output was 0V. Being variable speed fan, there should be other voltages out (don’t know what). I purchased a new fan control unit, installed and all WAS working fine.

Last week the Coolant – Visit Workshop light came on.
Checked the fan, runs high speed when connected to 12V, runs low when defrost is on. The fan does not run when the car is on and between 80-110F. 80-90F is the normal temp. Outside temps have been about 60, so the car temp does not get to 100 very often (unless in stop and go traffic).
It appears the fan has some other device controlling it if it will run when the defroster is on.
Before I purchase another fan control unit, does anybody know of any other item that might be bad? Temperature sensor? Thanks

 

^Coolant temperature sensor.

 

how do you test the fan with 12volts?

 

Fan

Sold the Benz in January, maintenance cost started to climb, got an Acura TL.

Disconnected connector near the motor. I used a 12v battery jump start pack and connected it to the motor wires. You can also use jumper cables from a battery. Use care.