Turn signals randomly quit working - Yikes!
Thread Starter
Newbie
Joined: Sep 2017
Posts: 11
Likes: 3
From: Seattle, WA, USA
2012 ML350 Bluetec
Turn signals randomly quit working - Yikes!
Bought a 2012 ML350 Bluetec (60k miles) for the GF to drive. Great car, love the torque and economy but there is a big problem. Sometimes immediately and sometimes after 5-10 miles, the turn signals completely stop working. Dangerous to say the least. I thought it might be related to the blind spot assist, so I turned that off but the problem persists. I've looked for answers on the forums and although at least one other person had the same issue, there was no solution presented. Is this issue really that rare?
Thread Starter
Newbie
Joined: Sep 2017
Posts: 11
Likes: 3
From: Seattle, WA, USA
2012 ML350 Bluetec
Yes there is a solution, its a simple circuit consisting of the stalk, the relay and the front SAM, your issue is that you want a free solution and that there isn't------find someone with DAS Xentry tester and you will learn the solution in five minutes----else--live with it!
Ummm, nice 'effort' Plutoe, but try again. My 'issue' is that I'd like to be more informed about the system, how it works, what it interfaces with and what the common (if there is one) failure point is in said system. In case you've forgotten, that's one of the primary things these forums are good for - knowledge. IMHO - there is no better way to minimize the chances of being screwed by a service department (dealer or independent) than to know exactly how something works, so when they make a suggestion, your only option isn't to just nod your head, say OK, open your wallet and hope they know what they are doing.
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Joined: Dec 2016
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From: at the mercedes dealer next to you
2020 GLE350 2020 Toyota Rav4H AWD XLE
Ummm, nice 'effort' Plutoe, but try again. My 'issue' is that I'd like to be more informed about the system, how it works, what it interfaces with and what the common (if there is one) failure point is in said system. In case you've forgotten, that's one of the primary things these forums are good for - knowledge. IMHO - there is no better way to minimize the chances of being screwed by a service department (dealer or independent) than to know exactly how something works, so when they make a suggestion, your only option isn't to just nod your head, say OK, open your wallet and hope they know what they are doing.
Thread Starter
Newbie
Joined: Sep 2017
Posts: 11
Likes: 3
From: Seattle, WA, USA
2012 ML350 Bluetec
UPDATE TO SYMPTOMS
It seems like the 'cancel' function (turn signals automatically turn off when turning the steering wheel in the opposite direction from the actuated signal) is also erratic. Sometimes it doesn't cancel unless you tap the stalk in the opposite direction. I've had that mechanism apart on several other vehicles I've owned and it's always been a simple mechanical device on the steering column. Has Mercedes 'modernized' this tried and true design and made the turn signal cancel function purely electronic?
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Joined: Mar 2004
Posts: 1,175
Likes: 24
From: Boston, MA
'14 ML350, '13 C220 CDI, '07 C280, '98 ML320
It seems like the 'cancel' function (turn signals automatically turn off when turning the steering wheel in the opposite direction from the actuated signal) is also erratic. Sometimes it doesn't cancel unless you tap the stalk in the opposite direction. I've had that mechanism apart on several other vehicles I've owned and it's always been a simple mechanical device on the steering column. Has Mercedes 'modernized' this tried and true design and made the turn signal cancel function purely electronic?
Member
Joined: Jul 2012
Posts: 102
Likes: 58
From: Chicago
2020 GLE450 / 2003 BMW M5
Bought a 2012 ML350 Bluetec (60k miles) for the GF to drive. Great car, love the torque and economy but there is a big problem. Sometimes immediately and sometimes after 5-10 miles, the turn signals completely stop working. Dangerous to say the least. I thought it might be related to the blind spot assist, so I turned that off but the problem persists. I've looked for answers on the forums and although at least one other person had the same issue, there was no solution presented. Is this issue really that rare?
May not be be the same problem, but it seemed SAM modules can cause pretty strange electronic behavior despite everything else seeming normal. Since having them replaced, no other odd behavior. Not sure if there’s a handy way to repair a defective module, but the service advisor told me how many different electronic control components were in the ML and I was surprised.
Thread Starter
Newbie
Joined: Sep 2017
Posts: 11
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From: Seattle, WA, USA
2012 ML350 Bluetec
I'm leaning towards it being a purely electronic issue as shutting off the ignition and restarting the vehicle causes it to work again every time, if only momentarily. It does seem to be getting worse as time goes on. I have an appointment for Monday at a trusted independent with the correct MBZ full-on chassis computer. He 'should' be able to diagnose it. I'll certainly post with the results.
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Thread Starter
Newbie
Joined: Sep 2017
Posts: 11
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From: Seattle, WA, USA
2012 ML350 Bluetec
In preparation for meeting with the mechanic, it would be great to know how many SAMs there are in the vehicle and their location/function. I saw a GREAT write up on another forum regarding SAMs in a S500 but can't find anything comparable for the W166. Are there separate left and right front SAMs or just one for the front? Might be worth putting eyes on the one responsible for the turn signals and checking that everything looks to be plugged in and 'normal' prior to taking it to the shop.
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Member
Joined: Feb 2003
Posts: 238
Likes: 9
From: Toronto
2009 e class 2012 ml350
Bought a 2012 ML350 Bluetec (60k miles) for the GF to drive. Great car, love the torque and economy but there is a big problem. Sometimes immediately and sometimes after 5-10 miles, the turn signals completely stop working. Dangerous to say the least. I thought it might be related to the blind spot assist, so I turned that off but the problem persists. I've looked for answers on the forums and although at least one other person had the same issue, there was no solution presented. Is this issue really that rare?
Thread Starter
Newbie
Joined: Sep 2017
Posts: 11
Likes: 3
From: Seattle, WA, USA
2012 ML350 Bluetec
When you had this issue, would turning the ignition off and back on 'reset' the system and make the turn signals work again? I'm trying to understand how a simple electro-mechanical item can fail in that way, but I suppose since the output from that item feeds into a module (not directly to the bulbs) anything is possible.
Member
Joined: Feb 2003
Posts: 238
Likes: 9
From: Toronto
2009 e class 2012 ml350
When you had this issue, would turning the ignition off and back on 'reset' the system and make the turn signals work again? I'm trying to understand how a simple electro-mechanical item can fail in that way, but I suppose since the output from that item feeds into a module (not directly to the bulbs) anything is possible.
Member
Joined: Aug 2007
Posts: 228
Likes: 39
From: Peoria, IL
2007 C350 2015 ML400 1968 Ford Mustang
Second, while the signal is a switch, the input of the switch is read by the Steering Control Module at the top of the column. Then that signal is communicated to the Front SAM via CAN. If after the signals quit working, but you can get your hazards to come on, I would suggest that your SCM be replaced. Hazards are requested by the Upper Control Panel over LIN, but also to the Front SAM. The front SAM is located on the right side of the dash directly under the A pillar.
Senior Member
Joined: Mar 2016
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Likes: 49
C43 Coupe
This happened to my father's ML350 BT, same model year. We ended up having to have the whole steering column unit replaced. It cost us $1100 CAD through the dealer. If you would like, I can dig up the diagnostic sheet, and upload a pic for you.
Thread Starter
Newbie
Joined: Sep 2017
Posts: 11
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From: Seattle, WA, USA
2012 ML350 Bluetec
Yes, that would be great - Thanks. Truck is at the mechanic's today and it would be great to be able to match up your diagnostic with his...
Thread Starter
Newbie
Joined: Sep 2017
Posts: 11
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From: Seattle, WA, USA
2012 ML350 Bluetec
Here is the diagnostic printout. Note that this is after the tech cleared the existing codes and then drove the car around for a bit. During his drive, the turn signals and blind spot assist worked fine BTW. Seems strange that it takes a while for the errors to build up to the point of turn signal failure though. Any ideas?
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C43 Coupe
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Joined: Sep 2013
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2001 E320, 2010 E350 Sedan, 2009 E350 Wagon, 2014 E350 Coupe, 2015 ML 350
I had this problem on my 2014 ML 350, supposedly. I never saw it but it happened at the dealer when they were trying to diagnose an issue with the sunroof. that was at 28k miles a few months ago. Now My driver side rear turn signal isn't working at all! LED strip is out cold. At least the car is smart enough to use the brake light as the turn signal now, Anyone else have this problem? It has been raining where I'm at all day so maybe moisture got in there?
Have to say I am disappointed with this car. I'm only at 32,000 miles and have had so many issues. More than I've had with my 2001 E320 that has 140,000 on it.
Have to say I am disappointed with this car. I'm only at 32,000 miles and have had so many issues. More than I've had with my 2001 E320 that has 140,000 on it.
Thread Starter
Newbie
Joined: Sep 2017
Posts: 11
Likes: 3
From: Seattle, WA, USA
2012 ML350 Bluetec
Thanks Tej7. Certainly looks very similar to my issue. I have a replacement assembly coming from an auto dismantler ($200, with warranty) and the install looks very straightforward. Likely have to have it coded at my mechanic's shop but we'll see (same year and model donor car so I might get lucky.) I'm definitely going to dig into the old switch itself and see if there is anything obviously wrong mechanically or with the electrical contacts/connections. If I find something fixable, I'll post the solution here.
Member
Joined: Aug 2007
Posts: 228
Likes: 39
From: Peoria, IL
2007 C350 2015 ML400 1968 Ford Mustang
Thanks Tej7. Certainly looks very similar to my issue. I have a replacement assembly coming from an auto dismantler ($200, with warranty) and the install looks very straightforward. Likely have to have it coded at my mechanic's shop but we'll see (same year and model donor car so I might get lucky.) I'm definitely going to dig into the old switch itself and see if there is anything obviously wrong mechanically or with the electrical contacts/connections. If I find something fixable, I'll post the solution here.
Thread Starter
Newbie
Joined: Sep 2017
Posts: 11
Likes: 3
From: Seattle, WA, USA
2012 ML350 Bluetec
New (used) part is in and the both turn signals and blind spot warning are functioning normally again. FYI - I did have to Youtube the airbag removal as Mercedes has done away with the two torx screws and gone to a simple push-to-release arrangement hidden underneath a couple of innocuous looking indentations in the back of the steering wheel. It was a 15 minute job and no recoding was needed with the new module. Next is to take apart the old turn signal switch and see if anything is obviously wrong with the mechanicals or visible contacts. I'll update with what I find (if anything.)
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Joined: May 2017
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From: Montreal/Cape Coral FL
2012 X6 35i Sport, 2013 ML 350 BT, 2019 4Runner TRD Pro, 2020 CRV-AWD
Another one-post wonder. Did you bother to read the whole thread?
Last edited by peter2772000; Jan 6, 2019 at 10:02 AM.
