E500E Electric Fan conversion thread

[gsxr]

@friendlymbtech, does this single fan installation make the dual auxilliary fans redundant?

@500AMM: Keep in mind the dual auxiliary fans were never intended for primary cooling. These fans have 2 functions, when used with the mechanical/viscous clutch:

1) At low fan speed (through the resistor behind the headlight), the twin fans provide additional airflow at low vehicle speed / low engine RPM, i.e. when sitting in traffic. This is meant to aid in AC performance, it isn't meant to cool the engine. The low speed triggers based on refrigerant pressure - turns on at 16 bar, off at 12 bar (232 psi on, 174 psi off). Low speed won't trigger at all, ever, based on engine/coolant temp. The fans make a large, rapid change in refrigerant pressure when they cycle on/off. On a warm day with AC running, connect manifold gauges and watch the high side pressure as the fans cycle. This video shows the gauges and if you listen closely, you can hear when the fans are turning on/off... unfortunately there was some annoying wind noise (sorry).​

​

2) At high fan speed, the the twin fans trigger at 107°C coolant temp, based on a signal from the 2-pin temp sensor to the HVAC control unit, which trigger the high speed fan relay. The fans will turn off at something like 98°C coolant temp. This is to aid engine cooling (not AC performance), once again at low vehicle speed / low engine RPM. At higher speeds/RPM, the viscous clutch is supposed to move enough air to keep things cool, or at least keep the engine below 107°C. With a good fan clutch (engaging correctly), it's abnormal for engine temps to reach 107°C when the cooling system is all in top shape.​

So, in light of the above, Arnt... the single fan installation DOES make the dual auxiliary fans redundant, as long as the single fan can receive a signal from the AC system to run the fan at a low speed when refrigerant pressure is high enough. This should be possible if the controller has an auxiliary input, which could be wired to the factory red refrigerant pressure switch at the receiver/drier. (Note - both the controller friendlymbtech used, and the controller Jlaa plans to use, have an AC input to run the fan with air conditioning.)

In theory you could sort of skip this AC-triggered function if the single fan runs at low coolant temp, but I personally would want the single fan to be completely off until engine coolant temp exceeds 90-95C or so, then have the fan speed ramp up proportionally with coolant temp. The nice thing here is each person can dial in the temp settings to their personal preference.

The downside here is that there's a slight possibility of high refrigerant pressures with low coolant temp, where the single fan may not run at all. Also, with only a single fan, there is no redundant cooling backup. The twin fans don't weigh much and shouldn't restrict airflow, so I'd be tempted to leave them installed as a backup in case something goes awry with the single/primary fan.

 

[Kridre]

@friendlymbtech Wouldn't it be better to tape/glue the sensor to the bottom of the radiator instead of cutting the bottom hose? You could use some thermal paste and aluminum bracket to hold it in place there. I think this would result in a much better looking installation. I don't think there would be much off a difference in the temperature between the hose and bottom of the radiator.

 

[friendlymbtech]

@friendlymbtech Wouldn't it be better to tape/glue the sensor to the bottom of the radiator instead of cutting the bottom hose? You could use some thermal paste and aluminum bracket to hold it in place there. I think this would result in a much better looking installation. I don't think there would be much off a difference in the temperature between the hose and bottom of the radiator.

Coolant doesn't flow through the very bottom of the radiator. It looks just like the top. The very top and bottom caps of the radiator don't have coolant passages. There are fins between the top and bottom and the coolant passages so changes in temperature noticed by the sensor would not be as accurate or immediate as a sensor making contact with something that is also making direct contact with coolant.

 

[Kridre]

Oh, I didn't know that, thanks for the information. I will definitely keep this in mind when I will do electric fan conversion in the future.

 

[500AMM]

@500AMM: Keep in mind the dual auxiliary fans were never intended for primary cooling. These fans have 2 functions, when used with the mechanical/viscous clutch:

1) At low fan speed (through the resistor behind the headlight), the twin fans provide additional airflow at low vehicle speed / low engine RPM, i.e. when sitting in traffic. This is meant to aid in AC performance, it isn't meant to cool the engine. The low speed triggers based on refrigerant pressure - turns on at 16 bar, off at 12 bar (232 psi on, 174 psi off). Low speed won't trigger at all, ever, based on engine/coolant temp. The fans make a large, rapid change in refrigerant pressure when they cycle on/off. On a warm day with AC running, connect manifold gauges and watch the high side pressure as the fans cycle. This video shows the gauges and if you listen closely, you can hear when the fans are turning on/off... unfortunately there was some annoying wind noise (sorry).​

​

2) At high fan speed, the the twin fans trigger at 107°C coolant temp, based on a signal from the 2-pin temp sensor to the HVAC control unit, which trigger the high speed fan relay. The fans will turn off at something like 98°C coolant temp. This is to aid engine cooling (not AC performance), once again at low vehicle speed / low engine RPM. At higher speeds/RPM, the viscous clutch is supposed to move enough air to keep things cool, or at least keep the engine below 107°C. With a good fan clutch (engaging correctly), it's abnormal for engine temps to reach 107°C when the cooling system is all in top shape.​

So, in light of the above, Arnt... the single fan installation DOES make the dual auxiliary fans redundant, as long as the single fan can receive a signal from the AC system to run the fan at a low speed when refrigerant pressure is high enough. This should be possible if the controller has an auxiliary input, which could be wired to the factory red refrigerant pressure switch at the receiver/drier.

In theory you could sort of skip this AC-triggered function if the single fan runs at low coolant temp, but I personally would want the single fan to be completely off until engine coolant temp exceeds 90-95C or so, then have the fan speed ramp up proportionally with coolant temp. The nice thing here is each person can dial in the temp settings to their personal preference.

The downside here is that there's a slight possibility of high refrigerant pressures with low coolant temp, where the single fan may not run at all. Also, with only a single fan, there is no redundant cooling backup. The twin fans don't weigh much and shouldn't restrict airflow, so I'd be tempted to leave them installed as a backup in case something goes awry with the single/primary fan.

Many thanks for a proper explanation, it's interesting to learn how this works. I'll leave the aux. fans in place, good to have as a back up.

 

[Jlaa]

Interesting... he is using a controller from AutoCoolGuy, that cost $285 plus accessories. I hadn't heard of this one before. Not sure I'm impressed with the design or features vs the Dave Brown Controller (link) which is only $150.

For what it is worth --- after watching @friendlymbtech in the YouTube video cut the wires to the MB CLA electric fan and extend them ---

The AutoCoolGuy controller seems to want to control the fan directly, and wants to provide big current to the fan. This controller is the actual PWM controller. Looking at its system block diagram on the website, on can see lots of amps going directly from the battery through the controller to the fan. Note that there is one knob which controls the temperature at which this controller starts to turn on (at a low speed) ...... and then this controller automatically scales up the fan speed as the temperature increases.



The Microauotonomations v3 controller (Dave Brown Controller) on the other hand supplies control input to the Mercedes fan and relies on the MB OE PWM controller built into the fan. Because of this, the Microautonomations v3 controller is not a high-current device, and the fan in this instance is wired directly to the battery. Note that this controller has two programming set points, instead of one "turn on temp" via knob like the AutoCoolGuy device. This controller's set points are:

- The temperature at which the fan starts to spin at 25% speed
- The temperature at which the fan should be spinning at 75% speed

The controller will then automatically control the speed to scale between these two set points, and then past that to 90% speed.

 

[500AMM]

@Jlaa is it any potential risk for meltdown at a given scenario?

 

[friendlymbtech]

For what it is worth --- after watching @friendlymbtech in the YouTube video cut the wires to the MB CLA electric fan and extend them ---

The AutoCoolGuy controller seems to want to control the fan directly, and wants to provide big current to the fan. This controller is the actual PWM controller. Looking at its system block diagram on the website, on can see lots of amps going directly from the battery through the controller to the fan. Note that there is one knob which controls the temperature at which this controller starts to turn on (at a low speed) ...... and then this controller automatically scales up the fan speed as the temperature increases.

View attachment 184084

The Microauotonomations v3 controller (Dave Brown Controller) on the other hand supplies control input to the Mercedes fan and relies on the MB OE PWM controller built into the fan. Because of this, the Microautonomations v3 controller is not a high-current device, and the fan in this instance is wired directly to the battery. Note that this controller has two programming set points, instead of one "turn on temp" via knob like the AutoCoolGuy device. This controller's set points are:

- The temperature at which the fan starts to spin at 25% speed
- The temperature at which the fan should be spinning at 75% speed

The controller will then automatically control the speed to scale between these two set points, and then past that to 90% speed.

View attachment 184086

View attachment 184085

The AutoCoolGuy controller controls the ground side of the fan. Positive side of the fan is wired directly to the battery. The "fan" terminal goes to the ground and the "GND" also goes to ground. For the Dave Brown controller, two additional wires would be needed to wire the factory fan PWM module for the CAN/LIN. The AutoCoolGuy controller seems to have more of a universal application vs needing to be wired to an already PWM controlled fan since the AutoCoolGuy IS the PWM controller vs Dave Brown controlling an already existing PWM controller. Maybe that's why the ACG controllers are rated for high current. I got the 150 AMP version. He also makes 85 AMP and 125 AMP. 150 is overkill but I like having too much vs not enough.

 

[xfadmin]

We love @friendlymbtech here.

 

[Jlaa]

@Jlaa is it any potential risk for meltdown at a given scenario?

I suppose the question is if one prefers to rely on the transistors / design inside the OE MB electric fan unit or in the autocool guy unit, but right now @friendlymbtech is the only one who is actively experimenting —- and we all benefit! The rest of us are researching…. Taking it slowly and accumulating knowledge….

Who would have thought that Jelmer’s original project would continue living a decade and half later….

 

[gerryvz]

I think that Mr. FNT (@friendlymbtech) should start an OWNER thread in that sub-forum, and post links to his M119 rebuild videos (and other repair videos). It will add to the knowledge base here.

Oh, and given their common mother-ship employer, I wonder if @Klink and @friendlymbtech know each other?

 

[500AMM]

The question I posted in post #95 about the el.fan conversion making the two aux.fans for the AC redundant, is by far answered already by @Markus-MD in this thread:

Visco Fan delete | M119 Engine

Here my new Projekt.I dont like the Viscofans too laud too inefecktiv too bad to expensive and so on.Now i have with two good friends create a solution for replace/delete this terrible thing.One is an Electronic Engineer and the oter is from Petrol drilling company.this actualltiy in the...

www.500eboard.co

Another thing is to keep them as a back up for safety reasons, but how often does the singel fan fail on the W205 and W212, probably never.

 

[friendlymbtech]

The question I posted in post #95 about the el.fan conversion making the two aux.fans for the AC redundant, is by far answered already by @Markus-MD in this thread:

Visco Fan delete | M119 Engine

Here my new Projekt.I dont like the Viscofans too laud too inefecktiv too bad to expensive and so on.Now i have with two good friends create a solution for replace/delete this terrible thing.One is an Electronic Engineer and the oter is from Petrol drilling company.this actualltiy in the...

www.500eboard.co

Another thing is to keep them as a back up for safety reasons, but how often does the singel fan fail on the W205 and W212, probably never.

That's actually a really good point. I can't remember the last time I replaced a cooling fan because it failed. It was probably on a W203 or W204.

 

[friendlymbtech]

Quick update. I drove the car from Southern California to Phoenix this weekend. The whole time the coolant temperature barely moved. It sat right above 80°C the whole time except when going uphill for an extended period like the Chiriaco Summit when it would only increase a needle width or two. I even increased the temperature at which the fan would turn on. Then there's the fuel mileage...every time I have made that trip in this car, I'd have to top off in Blythe because I wouldn't make it there on one tank. When I topped off just over the Arizona border in Ehrenberg I had averaged 23.2 mpg. I have never gotten more than 20 mpg on this trip using cruise control the whole way. Mind you, this leg of the trip had been mostly uphill to that point. On the return trip I filled up at the same gas station without filling up in between. So that whole round trip from gas station to gas station was 282 miles. When I arrived back at the gas station, the gauge wasn't even at 1/4 tank yet. After filling up, and even clicking the handle a few times, I did the math and for those 282 miles I averaged 25.7 mpg. That was cruise control at about 80 MPH also. I'd say a 5-6 mpg increase is pretty incredible. That's about 25-30% increase in fuel economy. So far I am very happy with the results of the AutoCoolGuy PWM fan controller.

 

[TerryA]

@friendlymbtech
That mileage is terrific! Maybe I missed it but which 124 model did you achieve this in.
A 124-036 or a 124-034? The 124-024 has a much lower rear end ratio of 2.24 vs the 124-036's 2.65 or 2.82 (not sure which). This would help increase the mileage greatly in the 400E420.

Just Curious

lol

 

[friendlymbtech]

@friendlymbtech
That mileage is terrific! Maybe I missed it but which 124 model did you achieve this in.
A 124-036 or a 124-034? The 124-024 has a much lower rear end ratio of 2.24 vs the 124-036's 2.65 or 2.82 (not sure which). This would help increase the mileage greatly in the 400E420.

Just Curious

lol

It's a 124.034

 

[yao500e]

hello everyone, amazingly informative thread. thank you.

Is there a more compact smaller PWM fan controller option that can be engine area?

a large pwm in the trunk isnt ideal.

thank you all.

 

[Jlaa]

hello everyone, amazingly informative thread. thank you.

Is there a more compact smaller PWM fan controller option that can be engine area?

a large pwm in thr trunk isnt ideal.

thank you all.

Yes, the microautonomations (Dave Brown) controller mentioned throughout the previous 116 posts can be found here - Micro Autonomations

 

[yao500e]

Yes, the microautonomations (Dave Brown) controller mentioned throughout the previous 116 posts can be found here - Micro Autonomations

much appreciated. thank you

 

[mike52787]

With the fan clutch failing in my E500 I've been weighing options, and decided an electric fan conversion is most likely the best option, and a totally reversible mod at that. After reading this thread, I sourced a 2009? W211 E350 fan and shroud from the junkyard as well as the connector pigtail and the microautonomations controller. Today I set to getting the fan shroud to fit up.

Moderator edit: Fan shown below is A2045400788 / 204-540-07-88, 600W.

The fan shroud needed a fair bit of trimming, but cut very easily with a jigsaw. This is the finished product.




After trimming there is plenty of clearance between the old fan idler pulley and the electric fan.



To attatch the shroud to the radiator I used some scrap aluminum flatbar and some existing holes in the radiator.



Finally, the view from the top. I am happy with the way it turned out, almost looks OEM.





Now that it's in, next steps are the wiring and programming the controller, Will update this thread once it's all together and working!

 

[Jlaa]

Awesome!! I am following your efforts with great interest!

 

[Wake isle]

For your consideration. It seems I read some of the MB fans are 80 amp at full song. Will try and find that shortly. If that is true, this is a touch shy. A/C override and a motorsport company of some years.

PWM Fan Controller, Flush surface mount sending unit

PWM Fan Controller, Flush surface mount sending unit PWM Controllers PWM Fan Controller, Push In Probe 16795 16796 16757 16752 16797

derale.com

 

[gsxr]

For your consideration. It seems I read some of the MB fans are 80 amp at full song. Will try and find that shortly. If that is true, this is a touch shy. A/C override and a motorsport company of some years.

PWM Fan Controller, Flush surface mount sending unit

PWM Fan Controller, Flush surface mount sending unit PWM Controllers PWM Fan Controller, Push In Probe 16795 16796 16757 16752 16797

derale.com

Some fans does not mean all fans. The Micro Autonomations controller is rated for MB fans up to 800W (roughly 55-65A). The W204 fan mike52787 installed is a 600W unit (40-50A). It would be unusual to have the fan running at 100% except with extreme conditions.

Also, the Derale controller will not work with the factory temp sensors, it only works with their stick-on temp sensor. And there are a number of reviews that report failed controllers after about 1 year.

 

[Wake isle]

Many thanks for the hive mind intelligence. Was my first post here and surely do not want to steer anyone in the wrong direction.

 

[Jlaa]

Many thanks for the hive mind intelligence. Was my first post here and surely do not want to steer anyone in the wrong direction.

@mike52787 just curious - are you replacing the alternator with a higher-output unit as well?

 

[mike52787]

@mike52787 just curious - are you replacing the alternator with a higher-output unit as well?

Yeah, I have a m113 5.4 from a 210 e55 lying around, I'm pretty sure that still has the 150a alternator on it. I was going to steal that and throw it on once all the proof of concept work was done. I'm still waiting on some stuff to finish the wiring but hopefully will have it done this week.

 

[gsxr]

@mike52787 just curious - are you replacing the alternator with a higher-output unit as well?

+1... read post #52 (click here) if you haven't already.

 

[TerryA]

Some fans does not mean all fans. The Micro Autonomations controller is rated for MB fans up to 800W (roughly 55-65A). The W204 fan mike52787 installed is a 600W unit (40-50A). It would be unusual to have the fan running at 100% except with extreme conditions.

Also, the Derale controller will not work with the factory temp sensors, it only works with their stick-on temp sensor. And there are a number of reviews that report failed controllers after about 1 year.

@gsxr,
After reading thru some of Derale’s Literature lists an MB FAN CLUTCH for an E500E! It looks like the original design MB clutch. It says they make fan clutches.
USMW is located in Santa Fe Springs, CA, that about 15 miles from me.

Anyway, Food for Thought, MB’s is NLA

 

[gsxr]

@gsxr,
After reading thru some of Derale’s Literature lists an MB FAN CLUTCH for an E500E! It looks like the original design MB clutch. It says they make fan clutches.
USMW is located in Santa Fe Springs, CA, that about 15 miles from me.

No such luck, Terry. That website shows a generic aftermarket viscous fan clutch (ACM / Vemo / etc), not OE/OEM Sachs/Horton. They are just reboxing the same aftermarket junk clutch that everyone else is hawking.

 

[mike52787]

Apologies for taking forever to update this thread, but the electric fan conversion is finally finished and working! I had the temporary (almost permanent) solution of using a simple toggle switch between the 2 signal terminals on the fan but running the fan full speed at all times was obviously not ideal. So this weekend I took the time to finally finish properly.

The microautonomations controller works fantastically so far, very pleased with how easy it was to configure and wire up. The controller is preconfigured to use a autometer 2258 single terminal temp sensor, so I got my hands on one from scamazon. Drilled and tapped 1/8 npt threads into the top of the water neck. This is the only irreversible part of the conversion, but if that bothers you i'm sure there is another way to add the temp sensor.

I mounted the controller right above the alarm module under the passenger carpet and grabbed switched power from the cigarette lighter. Overall a very simple setup that seems to work well so far.

I'll update after putting some miles on this setup but so far i'm very happy with how it turned out.

 

[mike52787]

One more thing to add, the upper rad hose needs to be trimmed about half an inch on the water neck side to make clearance for the fan shroud. If not the upper rad hose will rub.

 

[Jlaa]

Wooohooo that is great to hear that this is working so well for you!!!

 

[Christian_K]

Raphael from Sterngarage in Germany also sells a very good Kit. I dont know which Fan he uses exactly, but i read the people are quite satisfied. The Fan runs unnoticable apparently.

 

[Markus-MD]

Has Raphael sell his Company?? And now is the CEO of this.Webshop is also different as ealier times.
I dont know exactly .You find no spare Sparts .Pistons Headgasket Blowerset .........after the v12 M275 was the cut.little bit sad:-((((

 

[gsxr]

SG's electric fan setup is documented at the link below. IMO this is a crude setup that is a downgrade from the mechanical viscous clutch. Using a factory electric PWM fan with Microauotonomations controller is vastly superior, IMO.

Thread 'Electric Fan Conversion - Stern Garage - SPAL Fan'

Apr 21, 2022

Moderator update: The Stern Garage "shop" links from their main website appear to be broken as of April 2025.

I saw this mentioned in passing some time ago and today I realized that SG now has this on their website:

W124 M119 Elektrolüfter Umbausatz für 400E, E420, E500, 500E, E60

Hiermit bieten wir Ihnen einen Umbausatz von Visco- auf Elektrolüfter an. Ideal für Modelle mit M119 Motor, die thermisch hoch belastet sind, wie W124 400E, E420, E500, 500E, E60. Hochwertige Aluminium Lüfterzarge in neuem Design mit einem extrem starken Spal-Lüfter. Der Umbausatz umfasst alle...

stern-garage-shop.com

It is EUR683.81, which doesn't seem unreasonable if put within the context of the price of an OE visco fan clutch.

EDIT - I cannot seem to find their email address though...

• Jlaa
• Replies: 25
• Forum: Heating and Cooling (Interior HVAC systems)

•