Engine fan: Difference between revisions

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'''Engine Electric Suction Fan (Cooling Fan) Threshold Temperature'''
== Engine fan ==
In STAR DAS and [[WIS]], the engine electric suction fan (cooling fan) is referred to as
"combustion engine and air conditioning with integrated control fan motor" and is designated M4/7.


Acknowledgement
[[File:M4 7 Engine Electric Suction Fan.png|400px]]


This DIY document was based on posts by MBWorld member ‘aleksandar1099’, ‘Jakpro1’, and ‘vrus’ and BenzWorld members ‘Saeed Amini’, ‘wallyp’, ‘jnash’ and 'Ex-Fed'
The electric fan (M4/7) is about 600W which means that large currents are required for it to operate.
The fan motor receives command pulses from the fan control unit.
In early vehicles the fan control unit was a separate part and mounted on the fan shroud.
On later models the fan control unit was built in to the fan motor.


This DIY document refers to both W211 and W220 models and may be relevant to other Mercedes-Benz models.
Each type of fan control unit employs PWM which stands for Pulse Width Modulation
and refers to the very efficient method for controlling the fan motor speed.
The voltage applied to the fan motor is "chopped" between 0V and 12V with the resulting fan speed being determined by the degree of "chopping".


STAR DAS can be used to adjust the “Correction programming of the electric suction fan for engine or air conditioning”.  “The correction is used for shifting the engine temperature dependence of the electric suction fan for engine or air conditioning”. That is adjust the Engine Electric Suction Fan (Cooling Fan) Threshold Temperature.
== Parts ==


Summary
* S500/S450/S350: A2205000193 600W


By changing the temperature at which the cooling fan on my 2003 W220 S500L comes on to a lower value, I have improved the performance of the car’s air conditioning on hot days.  The air coming from the cabin vents now feels sharp (cold) even when the car is idling at traffic lights.  Before the adjustment, the cabin became noticeably and uncomfortably warmer after idling for a few minutes.
Motor and relay are not sold separately, but used parts can be purchased on eBay.


Note my air conditioner is permanently left on at 22°C or 23°C in automatic mode. In my opinion the ACC now works as M-B intended, that is completely effectively, even in extremely hot climates, and quite unobtrusively, befitting the performance and elegance of an ‘S’ Class.
{|
|[[File:W220_engine_fan_A2205000193_front.jpg|thumb|none|A2205000193 front]]
|[[File:W220_engine_fan_A2205000193_back.jpg|thumb|none|A2205000193 back]]
|[[File:W220_engine_fan_motor_and_relay.jpg|thumb|none|Motor and relay]]
|}


In the process I discovered a fabulous tool for wirelessly logging data from my car to my Smart Phone and Desktop Computer.
== Wiring ==


Detailed Engine Coolant Temperature versus time graphs (before and after adjusting the Temperature Correction Value) are shown.
The connector has 4 wires:
* Ground
* 12v positive
* 12v volt when ignition on
* ECM signal (PWM modulated duty cycle/speed)


Sample of data results: A Temperature Correction Value of 0°C (M-B Factory Setting) means the Engine Cooling Fan switches on at 97°C and off at 92°C.  This can clearly be seen in the sample graph.
=== Typical PWM control signals ===
These diagrams were obtained by observing Cathode Ray Oscilloscope (CRO) measurements of typical control signals and the engine fan voltages.


http://w220.ee/images/b/b7/Engine_Coolant_Temperature_with_0C_Threshold_Correction_Value.JPG
{|
|[[File:Suction Fan Control Signal Pulses at 10% PWM.png|thumb|none|10% or zero RPM condition]]
|[[File:Suction Fan Control Signal Pulses at 90% PWM.png|thumb|none|90% or full speed RPM condition]]
|}


Link to BenzWorld Thread and DIY pdf attachment at Post #49:
The control signals from the Fan Control Unit match the above diagrams except that the amplitude of the signals is about 3Vp-p instead of 12Vp-p.


http://www.benzworld.org/forums/w220-s-class/1735481-question-about-star-diagnosis-5.html
== Remove/install cooling fan ==
 
The cooling fan is attached to [[radiator]] by two clips and two bolts.
Fan removal requires detaching ATF cooling line from the bottom of the fan.
By using more patience and wiggling it is possible to remove the cooling fan without
draining [[radiator]] and detaching coolant hoses.
 
<!-- AR20.40-P-6800AB Remove/install fan shroud 24.1.06
ENGINES
112, 113 in MODEL 220
ENGINE 113 in MODEL 215
ENGINE 113.963 in MODEL 230.475
ENGINE 113.992 in MODEL 230.474
ENGINE 112.973 in MODEL 230.467
ENGINE 113.995 in MODEL 230.472
-->
 
{|
|[[File:W220_remove_install_engine_fan_shroud.png|400px]]
|Shown on model 220 with M112:
* 1 - Fan shroud
* 2 - Coolant line
* 3 - Fastening shackle
* 4 - Retaining lug
|}
 
# Drain coolant from radiator
# Remove left air intake pipe to air filter
# Unscrew bolts from retaining tabs (3) on fan shroud (1)
# Disconnect electric plug connections for suction fan
# Detach expansion reservoir coolant line on coolant line thermostat housing to engine radiator
# Detach coolant line (2) at bottom right on engine radiator
# ''Use Torx T25 socket to remove ATF cooling line at bottom of fan shroud (arrow). See the photo below.''
# Lever off ''two'' clips at top of fan shroud ''(see the photo below)''
# Remove fan shroud (1). Pull fan shroud with retaining tabs (4) out of retaining lugs on radiator.
# Install in the reverse order
# Check coolant level and cooling system for leaks
 
{|
|[[File:W220_engine_fan_clip.jpg|thumb|none|Clip tightening fan to [[radiator]] (there are two)]]
|[[File:W220_engine_fan_transmission_fluid_cooling_line.jpg|thumb|none|ATF cooling line attached to fan]]
|}
 
{|
|{{#ev:youtube|https://youtu.be/XGsTMF4OTT8|320|left|Fan removal by removing coolant hoses|frame}}
|{{#ev:youtube|https://youtu.be/8YuRJfDdWh0|320|left|Fan removal without removing coolant hoses|frame}}
|}
== Issues ==
A common cause of no fan rotation is a failed Fan Control Module, either external or inbuilt.
The large currents can stress electronic components and the car is a hostile environment with vibration, heat, and moisture all present in large quantities.
A weak component or electrical connection can also produce a large amount of heat due to the very high currents being controlled, thus leading to complete failure.
 
{|
|[[File:Suction Fan Motor A204 540 07 88 with cover removed.png|thumb|none|Fan motor A2045400788 with cover removed]]
|[[File:Suction Fan Motor A204 540 07 88 showing burnt solder joint.png|thumb|none|Burnt solder joint in fan motor]]
|}
 
Most enthusiasts replace a failed fan with a complete new unit but on later models with inbuilt fan control module,
it is possible to just replace the fan motor and controller with consequent savings on cost and shipping. Check eBay for suppliers of fan motors.
 
In case of a faulty motor or control module, it is possible to swap it from other OEM fan:
{|
|{{#ev:youtube|https://youtu.be/ZufpP3SkJ9M|320|left|Radiator Coolant Fan Module Replacement|frame}}
|}
 
== Adjust threshold temperature  ==
 
This DIY instructions refer to both W211 and W220 models and may be relevant to other Mercedes-Benz models.
 
STAR DAS can be used to adjust the "Correction programming of the electric suction fan for engine or air conditioning".
"The correction is used for shifting the engine temperature dependence of the electric suction fan for engine or air conditioning".
That is adjust the fan threshold temperature.
 
By changing the temperature (at which the cooling fan comes on) to a lower value, the performance of the car's air conditioning on hot days has improved.
The air coming from the cabin vents now feels sharp (cold) even when the car is idling at traffic lights.
Before the adjustment, the cabin became noticeably and uncomfortably warmer after idling for a few minutes.
Note my air conditioner is permanently left on at 22°C or 23°C in automatic mode.
 
Detailed engine coolant temperature versus time graphs (before and after adjusting the temperature correction value) are shown.
 
Sample of data results: A Temperature Correction Value of 0°C (MB factory setting) means the engine fan
switches on at 97°C and off at 92°C. This can clearly be seen in the sample graph.
 
[[File:Engine_Coolant_Temperature_with_0C_Threshold_Correction_Value.JPG|700px|center]]
 
In my opinion the ACC now works as MB intended, that is completely effectively, even in extremely hot climates, and quite unobtrusively,
befitting the performance and elegance of an S-class.
 
In the process, I discovered a fabulous tool for wirelessly logging data from my car to my Smart Phone and Desktop Computer. Refer to: [[Code Readers]]
 
This DIY document was based on posts by MBWorld member ‘aleksandar1099’, ‘Jakpro1’, and ‘vrus’ and BenzWorld members ‘Saeed Amini’, ‘wallyp’, ‘jnash’ and 'Ex-Fed'.
Refer to BenzWorld [http://www.benzworld.org/forums/w220-s-class/1735481-question-about-star-diagnosis-5.html thread] and DIY pdf attachment at Post #49.

Latest revision as of 10:39, 21 August 2025

Engine fan

In STAR DAS and WIS, the engine electric suction fan (cooling fan) is referred to as "combustion engine and air conditioning with integrated control fan motor" and is designated M4/7.

The electric fan (M4/7) is about 600W which means that large currents are required for it to operate. The fan motor receives command pulses from the fan control unit. In early vehicles the fan control unit was a separate part and mounted on the fan shroud. On later models the fan control unit was built in to the fan motor.

Each type of fan control unit employs PWM which stands for Pulse Width Modulation and refers to the very efficient method for controlling the fan motor speed. The voltage applied to the fan motor is "chopped" between 0V and 12V with the resulting fan speed being determined by the degree of "chopping".

Parts

  • S500/S450/S350: A2205000193 600W

Motor and relay are not sold separately, but used parts can be purchased on eBay.

A2205000193 front
A2205000193 back
Motor and relay

Wiring

The connector has 4 wires:

  • Ground
  • 12v positive
  • 12v volt when ignition on
  • ECM signal (PWM modulated duty cycle/speed)

Typical PWM control signals

These diagrams were obtained by observing Cathode Ray Oscilloscope (CRO) measurements of typical control signals and the engine fan voltages.

10% or zero RPM condition
90% or full speed RPM condition

The control signals from the Fan Control Unit match the above diagrams except that the amplitude of the signals is about 3Vp-p instead of 12Vp-p.

Remove/install cooling fan

The cooling fan is attached to radiator by two clips and two bolts. Fan removal requires detaching ATF cooling line from the bottom of the fan. By using more patience and wiggling it is possible to remove the cooling fan without draining radiator and detaching coolant hoses.


Shown on model 220 with M112:
  • 1 - Fan shroud
  • 2 - Coolant line
  • 3 - Fastening shackle
  • 4 - Retaining lug
  1. Drain coolant from radiator
  2. Remove left air intake pipe to air filter
  3. Unscrew bolts from retaining tabs (3) on fan shroud (1)
  4. Disconnect electric plug connections for suction fan
  5. Detach expansion reservoir coolant line on coolant line thermostat housing to engine radiator
  6. Detach coolant line (2) at bottom right on engine radiator
  7. Use Torx T25 socket to remove ATF cooling line at bottom of fan shroud (arrow). See the photo below.
  8. Lever off two clips at top of fan shroud (see the photo below)
  9. Remove fan shroud (1). Pull fan shroud with retaining tabs (4) out of retaining lugs on radiator.
  10. Install in the reverse order
  11. Check coolant level and cooling system for leaks
Clip tightening fan to radiator (there are two)
ATF cooling line attached to fan
Load video
YouTube
Fan removal by removing coolant hoses
Load video
YouTube
Fan removal without removing coolant hoses

Issues

A common cause of no fan rotation is a failed Fan Control Module, either external or inbuilt. The large currents can stress electronic components and the car is a hostile environment with vibration, heat, and moisture all present in large quantities. A weak component or electrical connection can also produce a large amount of heat due to the very high currents being controlled, thus leading to complete failure.

Fan motor A2045400788 with cover removed
Burnt solder joint in fan motor

Most enthusiasts replace a failed fan with a complete new unit but on later models with inbuilt fan control module, it is possible to just replace the fan motor and controller with consequent savings on cost and shipping. Check eBay for suppliers of fan motors.

In case of a faulty motor or control module, it is possible to swap it from other OEM fan:

Load video
YouTube
Radiator Coolant Fan Module Replacement

Adjust threshold temperature

This DIY instructions refer to both W211 and W220 models and may be relevant to other Mercedes-Benz models.

STAR DAS can be used to adjust the "Correction programming of the electric suction fan for engine or air conditioning". "The correction is used for shifting the engine temperature dependence of the electric suction fan for engine or air conditioning". That is adjust the fan threshold temperature.

By changing the temperature (at which the cooling fan comes on) to a lower value, the performance of the car's air conditioning on hot days has improved. The air coming from the cabin vents now feels sharp (cold) even when the car is idling at traffic lights. Before the adjustment, the cabin became noticeably and uncomfortably warmer after idling for a few minutes. Note my air conditioner is permanently left on at 22°C or 23°C in automatic mode.

Detailed engine coolant temperature versus time graphs (before and after adjusting the temperature correction value) are shown.

Sample of data results: A Temperature Correction Value of 0°C (MB factory setting) means the engine fan switches on at 97°C and off at 92°C. This can clearly be seen in the sample graph.

In my opinion the ACC now works as MB intended, that is completely effectively, even in extremely hot climates, and quite unobtrusively, befitting the performance and elegance of an S-class.

In the process, I discovered a fabulous tool for wirelessly logging data from my car to my Smart Phone and Desktop Computer. Refer to: Code Readers

This DIY document was based on posts by MBWorld member ‘aleksandar1099’, ‘Jakpro1’, and ‘vrus’ and BenzWorld members ‘Saeed Amini’, ‘wallyp’, ‘jnash’ and 'Ex-Fed'. Refer to BenzWorld thread and DIY pdf attachment at Post #49.

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