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Outstanding Contributor , SDS Guru
1998 MB E300TD, 1997 MB E36 AMG, 2001 MB E55 AMG
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So.....you never checked the fan control module?
 

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Discussion Starter #22
My car's year is 2004 and its fan control module is part of the fan assembly (I am assuming that is being referred to as FCM). I tested the fan operation with SDS by lowering and increasing fan speed and it responded as expected. That means ECU is sending PWM commands to FCM. As mentioned previously, I have tried two other fans and exact same behavior.

SDS is showing the fan demand by Engine is zero. That means ECU has no reason to command the suction fan to turn on.

If I am looking at the wrong place, please let me know.
 

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Outstanding Contributor , SDS Guru
1998 MB E300TD, 1997 MB E36 AMG, 2001 MB E55 AMG
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Post last 8 number of your VIN. I am pretty sure you still have a separate fan control module by the airmatic pump.
 

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Discussion Starter #24
Here are the last 8 of the VIN 4A416618 , I am pretty sure the controller is part of assembly (at the bottom of the fan) and hardwired to the motor. The previous models had a box above the air pump and even the fan motor was on the corner.
 

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2005 SL65 plus 13 other non MB toys
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🥺 Really trying to save you money here my friend. Stop playing “parts darts” and do a proper diagnostic using SDS. 🥺

When I get down to the shop I’ll see if I can figure out the diagnosis procedure with SDS and report back.
 

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Discussion Starter #27
I will try quick test and post the result. I got the parts from junkyard at pretty low price as I pulled myself - I agree but throwing parts at the problem without proper diagnostics. Never dealt with radiator fan being so complex. Appreciate your expertise.
 

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Outstanding Contributor , SDS Guru
1998 MB E300TD, 1997 MB E36 AMG, 2001 MB E55 AMG
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Well, checked EPC with your vin, and you're correct you do not have a separate FCM. I remember a 2006 S500 did have a separate one, but maybe rules are different since your car is 4matic.

Check SDS, see what it says. Cooling fan diagram is super simple on this car...did you check fuses?
 

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Discussion Starter #29
Thanks for the nice diagram. Power checks was the first thing I did when I initially realized the issue with the fan. Both permanent ground, hot-wire and 2nd hot wire (switched when the key is moved to accessories) all good. I initially didn't understand PWM fans, after dealing with this car, I understood the technology. Now with all the diagnostics I have done, I think the fan is working as expected.

The issue is fan demand being zero. Based on your diagram, the coolant sensor is good, tested another new one as well ($10 original from eBay). Not sure with ECU, what is the trigger condition for it put demand on fan. Since, A/C is shot, I cannot try A/C load anymore.

I may have to eventually use a secondary thermal sensor to cut-off original thermal sensor input at 80 degrees and which will force the fan to run (I know my gauge will show zero while fan is running).
 

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Outstanding Contributor , SDS Guru
1998 MB E300TD, 1997 MB E36 AMG, 2001 MB E55 AMG
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Let the car keep running. On my W210 the fan kicks in around 100C.
 

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My SLK V8 project one kicked in at 20% around 94c when testing, but right now it's Version Coding is still as per when it was a V6 Car with a separate Controller & 450W Fan so that could be making it early, will see when it cuts in once I've re Coded it to the now fitted Integral Controller 600W Temic ;)

Still at least mine is actually working 🤣
 

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Discussion Starter #32
How do I get to the version coding through SDS? Any steps will be helpful.

I am not sure how would the ECU read anything from the fan controller - version number, coding etc?

Based on my understanding the PWM commands are one way - from ECU to the Fan controller using the 4th signal wre on the fan control unit.

There is no feedback to the ECU if fan is running or not. The fan motor has a speed sensor under the motor, which provides feedback to fan controller only. There are 4 wires from the controller to the fan motor (all look the same from outside). Three of them are thick copper wires for power to the motor coils and 4th wire is actually set of 4 low voltage wires, carrying signal and power to the sensor.
 

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Thanks for the nice diagram. Power checks was the first thing I did when I initially realized the issue with the fan. Both permanent ground, hot-wire and 2nd hot wire (switched when the key is moved to accessories) all good. I initially didn't understand PWM fans, after dealing with this car, I understood the technology. Now with all the diagnostics I have done, I think the fan is working as expected.

The issue is fan demand being zero. Based on your diagram, the coolant sensor is good, tested another new one as well ($10 original from eBay). Not sure with ECU, what is the trigger condition for it put demand on fan. Since, A/C is shot, I cannot try A/C load anymore.

I may have to eventually use a secondary thermal sensor to cut-off original thermal sensor input at 80 degrees and which will force the fan to run (I know my gauge will show zero while fan is running).
I am not sure why you are trying to keep engine at 80C. Thermostat does not begin to open until 87C. Rigging ECT will result in CEL.

Here are couple of documents describing suction fan function. I cannot find one specific for W220 but ML55 runs same engine controller ME2.8.
 

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Discussion Starter #34
Thanks. I will shortly try to warm up the car with new fan. Based on your document, it say 107 degree. I will try to see if it kicks in. I hope I get lucky this time.
 

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Discussion Starter #35 (Edited by Moderator)
Problem solved :) Thanks for everyone's help.

The fan kicked in around 98 degrees (at the end of temperature gauge segment segment above 80 degrees). Since my ML500 never goes above 80 degrees, I thought S430 was overheating as sometimes its fan would turn on around 80 degrees and sometime not. In the absence of specs, I thought my car was overheating.

I think thermostat opens at 80 degrees, but suction fan, as per the PDF sent by by Witek_M, kicks in 106.

I will summarize things which may help anyone dealing with the fan issue on W220 with an integrated controller. Things which I learnt the hard way. Please note I am not a professional mechanic, just a private individual with limited technical skills. Use the following at your own risk.

Important Notes
1. I highly recommend to have SDS software. Will save you time, money and you can get better help from experts in this group.
2. The suction fan, is a Brushless motor, which is basically an AC motor driven by a solid-state electronics controller. It will NOT run, like a regular DC motor, where you can apply 12v to two of the terminals. The controller for W220 fan gets its commands from the ECU on a single wire in the form of voltage pulses ranging from 0v to 12v. The ECU controls the speed of the fan, using Pulse Width Modulation PWM. Depending upon how long the pulse stays at 12v vs 0v (known as duty cycle of the pulse) controls the fan speed. Technically for W220, disconnecting the PWM signal will drive fan at the fastest speed (not recommended).

Following process assumes you you don't have SDS and/or other good quality diagnostics tools. For quick troubleshooting of the fan, check for the following voltages on the electrical connector at the top of the fan using a digital voltmeter.

a. Turn of the car
b. Check voltage from Thick Red Wire to Ground = +12v (it is hardwired through fuse)
c. Check Thick Brown Wire to Red Wire = +12 v (it is hardwired ground)
d. Turn car key to accessories
e. Check voltage from the wire (Red-Green) immediately below Brown ground wire (colors DO vary), should have +12v. This wire also goes through a fuse.
Note: Don't mess around with the 4th wire (Blue-Green) right below the Red wire. This wire carries PWM signal from the ECU. Unless you have an oscilloscope, I wouldn't mess around with it.

2. Start your car and make sure the temperature gauge rises as car warms up. I had Infrared thermometer for quick checks.

3. When temperature is around 106 degrees (you will need to guess where 100 degrees would be on gauge), the fan should turn on.

4. If the fan does not turn on and temperature is still going up, you want to trigger the fan to full speed. The way I did this was, I disconnected the small electrical connector for the engine temperature sensor. Note STOP the Engine first as connector is right above the belt. Carefully disconnect the connector (it is very fragile). After disconnecting the sensor, when you start the car, you will see temperature gauge will read zero (as expected) and the fan should run at full speed. This will happen if ECU and PWM signal circuit are working. If the fan runs, at the minimum you know your ECU appears to be good and talking to the fan controller.

5. Now if you can get hold of an SDS software, you can turn the fan on/off and even vary the speed to ensure ECU and Fan are communicating.

Few more tips:
1. One of the things you should know, the fan's connector is not water proof. So any water falling from the hood, washing the car and/or if you accidentally disconnect radiator hose, you will kill the fan controller.

2. Other models of Mercedes around similar years have the same fan controller and fan motor. The plastic radiator housing around fan might be different. You can easily remove the fan motor and controller and put it in your car. Don't forget the water damage warning above.

I again want to thank, especially Delpore and Witek_M, for taking time to guide me through this troubleshooting. The diagram and documents in the article are invaluable.
 

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This issue comes up in the spring just like mayo on oil cap in January. Weather is nice 75F, a/c off, windows down. Good fast run on the freeway then you get stuck at red light. Temp gauge keeps climbing and panic set off. :)

Connector for fan is splash proof in has nice silicone seal and all wires have seals at the connector.

There is nothing wrong checking PWM signal at YEBU wire. That signal is nothing more that increasing voltage.

Attached ME sheet 1, legend and diagnostics. Offending component is M4/7 at coords 48L. Follow wire from pin 4. It ends at ME connector 4, pin 39. Now in diagnostics sheet you will find expected values.
 

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Discussion Starter #37
Thanks Witek_M. Excellent and invaluable information.

For the fan connector, I should have been more clear in my post. The male connector has seal around it, however, the female connector of the control module itself is not water proof. The first fan I got from junkyard was full of water when I cut the plastic enclosure around it. Then I tried another fan from Craigstlist, was full of blue coolant. MB sealed the fan very well, however, the female connector is not waterproof. Even with the the fan module, they have silicone coated electronics, however, the daughter card within the module is not waterproof (not sure sure why they did it).

Thanks again for the information this morning. It brought my dilemma to an end and help me keep the S430, which I cannot find any other equivalent for - everything is high quality.
 

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I should have been more clear in my post. The male connector has seal around it, however, the female connector of the control module itself is not water proof.
Which is exactly why MB re oriented the Plug like this on later Cars :-



That is the Cooling Fan installed on my R170 V8 Project, it is a 2006 W203 C Class model 600W Temic Fan assy, the Controller is now inside the Hub of the actual Fan Motor ;)

I have had many W220 and C215 Cars in the Workshop with the common problem (Split Radiator Tank just under the Top Hose connector), and every single one has killed it's Fan Controller due to Coolant Ingress ;)

HTH
 
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