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2007 SLK280
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Discussion Starter · #1 ·
Winter time is time for tinkering so I decided to create a documentation of the front SAM capacitor replacement that I performed on my SLK today. There are some other threads here on this, but this one will contain more pictures.

My car is a 2007 SLK 280 171.454. The symptoms were a recurring fault code 9000 and sometimes after turning of the AC it would not turn back on unless I turned the engine off and back on.

I use a Delphi DS150e to read codes. MB Star Diagnose would be ideal, but any mb-specific aftermarket scanner (e.g. iCarsoft) should do the job just fine.

589821


Who or what is SAM? SAM stands for signal acquisition module which is just another name for a fancier fusebox. The front SAM is used to control various electrical functions within the engine bay like lights, wipers or HVAC.

The current part number for a front SAM is A1715451601 and while it is available it is not very cheap. It also needs some coding from MB or somebody who has Star Diagnose.
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What causes the issues are drying out electrolytic capacitors on the board of the SAM. There are four capacitors:

2x 50V 22µF
1x 50V 10µF
1x 35V 220µF

While you could measure them to see which one is bad I decided to replace all four since they cost basically nothing.
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The SAM is located in the compartment on the drivers side firewall while the battery is in the compartment under the passenger side firewall.
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First you need to disconnect the ground terminal of the battery. Yes, I'd rather have an original MB battery. You will need a 10mm wrench or socket.
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And here's the SAM. It is held in place by three T15 Torx screws. You will need to unplug the connectors, but the fuses and relays can stay in place.
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Then pull it out and unplug the eleventy billion plugs from the underside. Thanks to MB for making every plug different so that it can only be plugged into its specific location.
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And here's our freed SAM with all these plugs next to it.
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There's our SAM again, but this time on the work bench (or kitchen table in my case). You will notice that the part number does not match the one in the screenshot above. MB has replaced the SAM several times.
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To be continued...
 

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2007 SLK280
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10 Posts
Discussion Starter · #2 ·
Remove the back cover that is held on by plastic clips. Then you will need to remove three T10 Torx screws. (Not all of them as I did here)

589831


To expose the other side of the PCB and get access to the capacitors the casing needs to be cut open. Some people used a hot knife to do so, I chose a Dremel with a cutting wheel. Just be careful not to cut the PCB.
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And there's our exposed PCB. We can finally see the capacitors.
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Here's a closer look. I used my trusty old Ersa 60W Analog soldering station for the soldering work.
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All four caps replaced. While the shape is slightly different this is irrelevant. The voltage (V), capacity (µF) and polarity are important.
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A look at my fresh solder joints.
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After reassembling the SAM I chose to cover the cut areas with black electrical type. I could have used RTV, but since it sits under a cover that has its own gasket this should be good enough.
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Next the SAM went back into the car. After it was back in place with all connectors plugged back in I reconnected the battery and reset the window regulators. While doing so I noticed no errors on the dash.

I then deleted all stored diagnostic codes and tested all functions.
589838


After turning the engine on and off several times and also turning the AC on an off several times I once again pulled the diagnostic codes. 9000 did not come back.
589839
 

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2004 SLK350
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170 Posts
Awesome!

How much time did it take to reconnect SAM @wur10 ? 😅

I've received my capacitors yesterday, the plan is to do that on Saturday 🤞
 

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2007 SLK280
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Discussion Starter · #4 ·
Good luck! I think disconnecting and reconnecting the SAM took me the longest since there isn't very much room and the wires aren't long enough to do this comfortable while being able to see what you are doing.
 

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2010 SLK350
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263 Posts
My A/C is doing the exact same, will run initially and then once it is down to temp and shuts off it will not restart.
I have had it confirmed that it is the front SAM showing the fault, but it is whether I have the nerve to carry out the repair myself...........
 

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2007 SLK280
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Discussion Starter · #8 ·
Depending on which part you aren't comfortable with you could have an independent shop remove the SAM and/or an electronics repair shop replace the caps.
 

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2010 SLK350
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Parts/Capacitors ordered and should have evrything next week to attempt this repair whilst we are still in lockdown!!
Its the PCB work I don't like..........
 

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Discussion Starter · #11 ·
Good job! I can't wait for warmer days to be able to see how the AC behaves. Currently my car is in winter storage.
 

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2007 SLK280
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Discussion Starter · #12 ·
Update. I decided to retire my old multimeter from the 90s and got a new one that can also measure capacity. Three of the four replaced caps were good and within spec. One however had 106µF instead of the rated 22µF. There's the problem.
 

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2005 SLK350
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Did the same repair yesterday, it's fiddly but not hard at all, the most problematic for me was to get the old components out of the board, those solder-connections are really small and my iron was hardly hot enough.
After the repair I tried the ac and all seems to be working perfectly again, one of the old blue 22µF capacitors had a measured value of 96µF, the others were still within range.
I used a loose sawblade to cut through the plastic, it is only a few seconds work, no need for expensive toys.
Good luck to those that are up for the task, it is really straight forward, just take your time and go slow. ;)
 

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2006 SLK350
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Thanks for the write up! Having the same problem , but no fault code. Still go ahead and replaced all the cap, and it didn't work for me. Am guessing regas?
 

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2007 SLK280
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Discussion Starter · #15 ·
Thanks for the write up! Having the same problem , but no fault code. Still go ahead and replaced all the cap, and it didn't work for me. Am guessing regas?
Oops, I missed that one. If you're getting no codes and the compressor does not turn on the system might be low on refrigerant. It's probably best to have a shop hook their machine up to the system and check it.
 

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2007 SLK280
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Discussion Starter · #16 ·
592434


Finally it's becoming warmer and the salt is gone so I was able to perform a longer test drive during which I turned the AC on and off several times. I did get cold air and after that drive I hooked up my scanner to the car which showed zero codes. So for me the recap of the SAM was a success.
 

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View attachment 592434

Finally it's becoming warmer and the salt is gone so I was able to perform a longer test drive during which I turned the AC on and off several times. I did get cold air and after that drive I hooked up my scanner to the car which showed zero codes. So for me the recap of the SAM was a success.
Well, as always marked as Resolved but if this issue returns, please come back to this thread (do NOT create a new one) and we will update accordingly (y)
 

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2004 SLK350
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View attachment 592434

Finally it's becoming warmer and the salt is gone so I was able to perform a longer test drive during which I turned the AC on and off several times. I did get cold air and after that drive I hooked up my scanner to the car which showed zero codes. So for me the recap of the SAM was a success.
After the repair I also just went to service the AC.

There was about half of the gas in the system (full should be 670g).

AC working nicely.
 
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