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*Registered
2000 SLK200K
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409 Posts
Discussion Starter · #1 ·
Hi. I recently noticed that my ECU fan (inside the apparatus box) is not working (when the engine is running or key in pos 2). The multimeter reads 0 volts at the leads. I checked all the fuses on the K40 relay they are okay.

The car has no problems & no codes, runs fine except if I drive it hard, the left window stops responding temporarily, until it cools down. I am sure the exhaust heat effects the control units inside as the box is very close to exhaust and SC. I need to find the reason for no power to the fan before the electronics are fried.

Does any body know if there is a dedicated fuse for the fan or can it be set on & off via Star computer menu etc? I checked the forums but usually the problem is the fan not the power supply. Any suggestions are welcome.

I also plan to remove the fan and put on 12v to see if it is in good contition. But for sure need to sort the power supply first.

It is a FL 200K 6M.
:Beer:
 

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*Premium Member
2005 SLK55 AMG /2005 SLK350
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6,172 Posts
I never did find this blower motor in the wiring diagrams... It seems to get power from one of the cu's. Once you start removing the cu's its easy to find. I've replaced these on several occasions on pre-FL models.
 

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*Premium Member
2005 SLK55 AMG /2005 SLK350
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6,172 Posts
So this tells me the blower is attached to the MFCU/CCMpins 50 and 67... That's good... Do you have the pinout of the MFCU so you can measure voltage with the key on?
 

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*Registered
2000 SLK200K
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409 Posts
Discussion Starter · #5 ·
So this tells me the blower is attached to the MFCU/CCMpins 50 and 67... That's good... Do you have the pinout of the MFCU so you can measure voltage with the key on?
yes I will take the socket out and test that pins. I hope it's just a contact issue at the socket. Otherwise, as I could not find any fuses related to this circuit, will it mean the CCM is faulty? The good thing is that all other functions are that are controlled by the CCM seems to work fine.

If this doesn't work I will try to find out if the blower can be turned off&on by a menu in Star diagnostic computer.

If none of these work I plan to hook it to a switched power source in the fuse box.
 

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*Premium Member
2005 SLK55 AMG /2005 SLK350
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6,172 Posts
The diagnostics aren't clear, but it seems to also imply you should disconnect the A coupling (not sure which that is) and test pins 44 and 5 too - I assume they mean test at the harness - these pins are documented as circuit 30 and ground.
 

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*Registered
2000 SLK200K
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409 Posts
Discussion Starter · #9 ·
My N10-3 does not supply (+) voltage (probably circuit blew when fan stuck, having no fuse) so I added ADD-A-CIRCUIT with 5 amp fuse to fuse 33. (fuse 33 switches on with the ignition). Ground was ok, so I kept it connected to N10-3. Works fine since then.

I'd recommend to everyone to add a fuse to positive lead of the ecu fan even if it's working. They fail soon or later.

Also DIY'ers can check the opening of the hose that supplies fresh air to the fan during cabin filter service. Hose is located behind the footwell area. Mine was sucking the insulation foam around...:frown:
 

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Registered 1999 SLK230
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60 Posts
Glad someone mentioned this... I was going to ask if the fan motor is driven by a thermostat or if it is supposed to run full-time when ignition is on.

Mine doesn't run with the key on, so I'm wondering for myself if I need to perform a little bypass surgery.

--
M
 
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