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A/C cooling in my 2005 R171 SLK was intermittent for a few months (thankfully, not too much in the summer). This past winter, it became increasingly problematic, causing the windscreens and windows to fog up frequently (depending on humidity levels, the A/C compressor is supposed to kick-in in order to dehumidify incoming air before it is heated and blown into the cabin). Using an iCarsoft scanner, I saw this error code for the SAM: 9000 component or the signal line to the component a9 (ac compressor) has open circuit or short to ground

With the defogger on, I could also see that the A/C compressor would actually turn on reliably (to dehumidify incoming air before it got heated up and blown over the windscreen) but would fail to turn on during normal use of the climate control. Thus, while the defogger works effectively, humid air would be blown into the car during normal use of the climate control, with frequent use of the defogger making the cabin uncomfortably hot and noisy.

I fixed this issue by taking out the front SAM (fairly simple, but a bit time consuming), and prying it open. I ultimately had to cut off part of the plastic cover with a hot soldering iron at two edges and lifting it up and out. Apart from one overheated capacitor, everything else looked good. I replaced that capacitor (bought for 48 cts), and that tiny fix appears to have successfully fixed the A/C problems.

The common recommendation for any SAM issue is to replace it. Dealer had quoted 650 USD for a new module, and 480 USD for the labour to swap it out and code it (~1,200 - 1,300 total quote is common across many dealers). Unfortunately, local indie mechanics with DAS equipment indicate that modern SAM, including the R171 one, can only be coded by a dealer if purchased new. Used SAMs may not need coding, but aren't reliably tested.

If any of you face SAM issues, I would recommend trying to fix it as I did: Take it to your friendly electronics guru/tech to check out, or simply attempt to replace any burnt out components yourself (in many electronics, that's usually just a capacitor or two). I spent 0.48 USD (and an hour or two of my time), vs ~1,200 USD.

NB: apologies for the fuzzy pic. Too lazy to take out the SAM for clearer pics.
iCarSoft scanner, highly recommended, since it can scan specific equipment in the car, which can't be done with a standard OBDII scanner: https://www.amazon.com/iCarsoft-Genuine-Mercedes-Professional-Diagnostic/dp/B00IUIDFSS/ref=sr_1_1?ie=UTF8&qid=1516513786&sr=8-1&keywords=icarsoft+mercedes
 

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Discussion Starter #2
NB: To take out SAM, and unscrew the plastic cover over the SAM circuit board, you need a T10 and T12 torx bit socket.

Also, before taking out SAM, disconnect negative terminal of battery. Just the negative terminal needs be removed, but if you want to remove both terminals for whatever reason, remove the negative first because the chassis of the car is connected to the negative cable. If you started removing the positive cable instead, your wrench could hit the chassisaround the battery and cause a short (the chassis is connected to the battery's negative terminal, and your wrench to the positive). This will cause the wrench to get red hot, leaving one with severe burns (or jewelry, like wedding rings, welded to the wrench).
 

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Registered 2005 SLK350
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I agree that this is a post that should be kept around (sticky). Many early front SAM units have been replaced due to the A/C not functioning properly. Knowing that the issue can be resolved with a simple new capacitor is really good to know.

Thank you @kipmasi for sharing this information.
 

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Super Moderator UK SLK 55 AMG 2007
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Just a note, should this not work.


If you need a new SAM (or a second hand one):


You need to tell that SAM what option the car has.
To do this, You have to code it to you vin number.
If you have a das machine you can read the old one and transfer in the new one.
If the old one is dead you need codding.


My thanks to @i860 for confirming this. :tu:
 

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Super Moderator UK SLK 55 AMG 2007
Joined
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25,490 Posts
Just a note, should this not work.


If you need a new SAM (or a second hand one):


You need to tell that SAM what option the car has.
To do this, You have to code it to you vin number.
If you have a das machine you can read the old one and transfer in the new one.
If the old one is dead you need codding.


My thanks to @i860 for confirming this. :tu:
 

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A/C cooling in my 2005 R171 SLK was intermittent for a few months (thankfully, not too much in the summer). This past winter, it became increasingly problematic, causing the windscreens and windows to fog up frequently (depending on humidity levels, the A/C compressor is supposed to kick-in in order to dehumidify incoming air before it is heated and blown into the cabin). Using an iCarsoft scanner, I saw this error code for the SAM: 9000 component or the signal line to the component a9 (ac compressor) has open circuit or short to ground

With the defogger on, I could also see that the A/C compressor would actually turn on reliably (to dehumidify incoming air before it got heated up and blown over the windscreen) but would fail to turn on during normal use of the climate control. Thus, while the defogger works effectively, humid air would be blown into the car during normal use of the climate control, with frequent use of the defogger making the cabin uncomfortably hot and noisy.

I fixed this issue by taking out the front SAM (fairly simple, but a bit time consuming), and prying it open. I ultimately had to cut off part of the plastic cover with a hot soldering iron at two edges and lifting it up and out. Apart from one overheated capacitor, everything else looked good. I replaced that capacitor (bought for 48 cts), and that tiny fix appears to have successfully fixed the A/C problems.

The common recommendation for any SAM issue is to replace it. Dealer had quoted 650 USD for a new module, and 480 USD for the labour to swap it out and code it (~1,200 - 1,300 total quote is common across many dealers). Unfortunately, local indie mechanics with DAS equipment indicate that modern SAM, including the R171 one, can only be coded by a dealer if purchased new. Used SAMs may not need coding, but aren't reliably tested.

If any of you face SAM issues, I would recommend trying to fix it as I did: Take it to your friendly electronics guru/tech to check out, or simply attempt to replace any burnt out components yourself (in many electronics, that's usually just a capacitor or two). I spent 0.48 USD (and an hour or two of my time), vs ~1,200 USD.

NB: apologies for the fuzzy pic. Too lazy to take out the SAM for clearer pics.
iCarSoft scanner, highly recommended, since it can scan specific equipment in the car, which can't be done with a standard OBDII scanner: https://www.amazon.com/iCarsoft-Genuine-Mercedes-Professional-Diagnostic/dp/B00IUIDFSS/ref=sr_1_1?ie=UTF8&qid=1516513786&sr=8-1&keywords=icarsoft+mercedes

Thanks, this was the exact error code I get from the icarsoft scanner. Took it to dealer and it blows ice cold. But was not turning on before, so intermittent. Where is the Front SAM located and how to get to it? Also, how can you tell what capacitor or which part has the issue on the board?
 

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Interesting... I went thru that replacing front-SAM and I also did have those AC issues. I now have the latest version of front-SAM's. Theres five or six of them if I remember right. Wonder what are the diffirences...

If some one are interested I could sell my old unit for 50e plus shipping. Condensators looked good as far as I could see under circuit board.
 

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Registered 2005 SLK350
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2,204 Posts
Thanks, this was the exact error code I get from the icarsoft scanner. Took it to dealer and it blows ice cold. But was not turning on before, so intermittent. Where is the Front SAM located and how to get to it? Also, how can you tell what capacitor or which part has the issue on the board?
The front SAM is located under the hood on the drivers side all the way back closet to the windshield. It has fuses and relays in the top section and the SAM is the rest of the box. As mentioned in the original thread, the replaced capacitor was circled in the picture and was evident that it was overheated. Any other components that also look overheated should be replaced.

With respect with the dealer comment that other issues would be showing if the SAM was failing, there are plenty of posts here that only showed the A/C issue like yours and the dealer always wants to replace the compressor to only find that it is not the issue, but rather the front SAM (I think @kipmasi alluded to just that in his original post about lots of parts getting replaced before the SAM is eventually repalced).
 

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The front SAM is located under the hood on the drivers side all the way back closet to the windshield. It has fuses and relays in the top section and the SAM is the rest of the box. As mentioned in the original thread, the replaced capacitor was circled in the picture and was evident that it was overheated. Any other components that also look overheated should be replaced.

With respect with the dealer comment that other issues would be showing if the SAM was failing, there are plenty of posts here that only showed the A/C issue like yours and the dealer always wants to replace the compressor to only find that it is not the issue, but rather the front SAM (I think @kipmasi alluded to just that in his original post about lots of parts getting replaced before the SAM is eventually repalced).
Yes that's true, at least I have an honest service manager at dealer who says he would not recommend replacing the compressor right now because he didn't know exactly what is going on and it appears to work. The other dealer I took it to just blindly said to replace the compressor without checking anything else.

Are there pictures of how to take out, etc. and perform? I saw @kipmasi had a few pics but it was just of the unit itself. To know exactly to get to and take apart or get into.
 

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Registered 2005 SLK350
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Yes that's true, at least I have an honest service manager at dealer who says he would not recommend replacing the compressor right now because he didn't know exactly what is going on and it appears to work. The other dealer I took it to just blindly said to replace the compressor without checking anything else.

Are there pictures of how to take out, etc. and perform? I saw @kipmasi had a few pics but it was just of the unit itself. To know exactly to get to and take apart or get into.
Yes, too many service departments just throw parts at a problem instead of figuring out what is really going on. Glad to hear you have a smarter service manager.

For the pics, one is the bottom of the SAM after it has been removed from the car and the circuit board accessed by cutting off a little of the plastic of the SAM and sliding the board out.
 

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Yes, too many service departments just throw parts at a problem instead of figuring out what is really going on. Glad to hear you have a smarter service manager.

For the pics, one is the bottom of the SAM after it has been removed from the car and the circuit board accessed by cutting off a little of the plastic of the SAM and sliding the board out.
How do you remove it from the car so you can get the board out, any pics of this?
 

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Super Moderator UK SLK 55 AMG 2007
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25,490 Posts
Interesting... I went thru that replacing front-SAM and I also did have those AC issues. I now have the latest version of front-SAM's. Theres five or six of them if I remember right. Wonder what are the diffirences...

If some one are interested I could sell my old unit for 50e plus shipping. Condensators looked good as far as I could see under circuit board.

I think they need DAS/STAR coding to the car?
@i860
 

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Registered 2005 SLK350
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I think they need DAS/STAR coding to the car?
@i860
Yes, any front SAM (new or used) would need to be coded to the car. If you are just swapping out one old unit for another the DAS with developer mode can capture the coding from the old unit and once the new unit is in place DAS will use the captured coding to install in the replacement SAM.
 

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Thanks, do you have to remove the entire box unit unplugged or can you just get the card out while leaving everything else in intact?
I think it would be difficult to get the case open to remove the circuit board without it out removed from the car.
 
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