Hello Guys,

It was very bad few days ago that an oil hose leaked oil into the fan control unit. I couldn't find the fan easily so I have done the following to repair it, a used fan costs about 400 USD, the repair cost was only 220$ including installation.

The C-CLASS COOLING FANS CAME FROM THE SAME MANUFACTURER OF THE SL55 COOLING FAN. BEHR.

The C240 FAN Control Unit IS ECL 600W 12.5V, while the SL55 is ECL 850 W 13V. The control unit and the clutch of both have the exact fitment size.

I took the risk to give it a try, and it worked perfect for now. I have tried to drive it an hour and a half in a traffic jam, the temperature was fine.

 

Glad you got it fixed fairly quick and inexpensively. I can't believe a little oil caused it to fail? You would think it would just cool and lubricate...

 

Not at all man, engine oil leaked into the module, I imagine the module melted :P

 

I completed this repair on my 2003 SL55 yesterday. Symptoms...intermittent Red thermometer in Temp Gauge, car overheating, cooling fan not running. Found the 600 Watt controller/motor above from a 340 CLK at the wrecker for $25.
Remove the cooling fan assembly by removing one 10mm bolt at the top corner on each side. Disconnect what I assume is a transmission fluid cooling line about 12" down on the left (looking from where you will be working) side. No fluid came out. Disconnecting the plug from the controller is a bit of a battle but after that, the cooling fan lifted out easily. Motor and controller are secured with Torx 20 screws.Remove and discard the old motor/controller.
600W controller fits and screws in perfectly. Motor fits ok but is a little shallower than the 850W motor. You will need four 5M x 20 MM metric bolts (the original ones will be too short) and about 20 flat washers, or something to use as a 1/4" spacer). Without the spacer, the fan blades will bind on the shroud, because of the shallower 600W motor.
Getting the washers or spacer in place is a bit of a trick. I did it by getting the four 5M screws inserted through the fan, threads exposed and up, sitting on a table. Then I put 4 flat washers and a lock washer on each screw thread. Next I lined up the four holes in the motor and landed the motor as best I could on top of my fan/screw/washer assembly. Then, I slid the assembly to the edge of the table so I could support the bottom of the fan with one hand, the motor (sitting on top) with the other hand, and flipped it over while squeezing it tight so the washers can't fall out. Took a few tries but once oriented with the screw heads on top, with a little jiggling to find the motor thread holes, they screw in and tighten up pretty easily. Reinstall the assembly, and don't forget to reattach the transmission cooling line, Works great! With correct tools ready and parts in hand it can be completed in less than an hour.
For as long as I don't post here again, this repair (using a 600W instead of 850W), is working fine and highly recommended as a very inexpensive, easy repair..

 

Heya gang- Posting here my attempt after my W209 850watt speed controller quit and couldn't find an affordable replacement (3rd rodeo, btw). I appreciate your post about swapping and found a 600w so i thought I'd give it a go. I designed a custom spacer ring in Autodesk Inventor to key into the fan. Works well so far, but haven't put serious miles on it to check the cooling. I'm attaching the .stl file if you want to print one yourself. I had some ASA filament, as it's a bit higher temperature and I figure things could get hot under the hood. Fortunately there's a lotta convection right there (duh!) so it should stay within thermoplastic melting point of about 250c. I used 70% infill, but you could probably get away with less. Just trying to improve upon your fantastic findings above and stop the hemmoraging of cash on these cars designed to fall apart after they're returned from a 3-year lease. Love the M113 motor though!

 

Hey, nice work on the printed spacer! Beats my method with all the washers. My 600W motor continues to work perfectly in my 250,000 km SL55. $25 well spent.

 

Thanks, just a tweak on what you did... And that's great to hear about your 600w motor still working. I was wondering if this could be a longer-term solution. Lots more C240's in the Pick-A-Part yards. I just did a couple hours in LA traffic with a/c on and temp stayed right in the middle of the gauge. So far, so good! fwiw I updated the part below to have bevels on the inside for better fitment... photo just shows side bevels. Screw holes are exactly right at 112mm diameter and 5.2mm (snug) bolts in case anyone else is wondering.

 

That 600w fan still working?
I'm in the same situation with my '03 SL55. Intermittent warning light, fan not operating. I get 12v at the big cables on the car side when the fan should be on but the fan doesn't turn. I think the intermittent warning light is intermittent because on the road the fan spins enough from air moving through it that the message disappears. I did take apart the old controller. Destroyed the black plastic cover in the process. (The Germans really did not want us to go in there...) Nothing looks like it's cooked and no swollen capacitors. The board inside is not easy to look over though and the rectifiers are all coated in the PCB gel.
I have some similar Merc examples in a JY near me, so I'm going there Saturday. They may not be the 850W units.

 

Yes, still working great. Mootzer (below) has a good pic of a 3D piece he made to make the 600W unit fit easier than using washers.

 

Thanks!
I've got no access to a 3d printer. Any chance a ring is available to a forum member?

 

Update. No ring needed for me. The 600w unit bolted up perfectly. Great fix and thank you for sharing.