Right Rear Turn Signal Not Working
Thread Starter
Newbie
Joined: Mar 2019
Posts: 3
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2007 R500
Right Rear Turn Signal Not Working
The passenger-side rear turn signal shows 11-12V until I install the socket w/ a new bulb. When I do that, the voltage goes to 0. The same socket and bulb works fine on the driver-side.
Is this the rear SAM module failing?
Is this the rear SAM module failing?
Super Member
Joined: Jul 2009
Posts: 938
Likes: 53
From: Montreal, Canada
2005 C240 2011 R350
Do you get the bulb/lamp fault indication in your instrument cluster?
You do realize you have to turn ignition off, then on again to allow SAM to re-sense presence of bulb.
Check wiring too. Note that the SAM is electronic, it is not a physical contact relay. The output may float at 12V with no resistance, but reduce to 0v when you install the light into the circuit.
How does the other side behave? same voltages with/without the bulb?
You do realize you have to turn ignition off, then on again to allow SAM to re-sense presence of bulb.
Check wiring too. Note that the SAM is electronic, it is not a physical contact relay. The output may float at 12V with no resistance, but reduce to 0v when you install the light into the circuit.
How does the other side behave? same voltages with/without the bulb?
Thread Starter
Newbie
Joined: Mar 2019
Posts: 3
Likes: 0
2007 R500
It never senses that the bulb is missing/defective unless I remove the bulb from the socket. Wiring looks OK from what I can see, but I haven't traced it from the SAM to the bulb.
The driver-side works perfectly. The running lamps/brake lamps/reverse lamps on the passenger side work fine, also. It's only the turn signal that doesn't work.
The driver-side works perfectly. The running lamps/brake lamps/reverse lamps on the passenger side work fine, also. It's only the turn signal that doesn't work.
Do you get the bulb/lamp fault indication in your instrument cluster?
You do realize you have to turn ignition off, then on again to allow SAM to re-sense presence of bulb.
Check wiring too. Note that the SAM is electronic, it is not a physical contact relay. The output may float at 12V with no resistance, but reduce to 0v when you install the light into the circuit.
How does the other side behave? same voltages with/without the bulb?
You do realize you have to turn ignition off, then on again to allow SAM to re-sense presence of bulb.
Check wiring too. Note that the SAM is electronic, it is not a physical contact relay. The output may float at 12V with no resistance, but reduce to 0v when you install the light into the circuit.
How does the other side behave? same voltages with/without the bulb?
Thread Starter
Newbie
Joined: Mar 2019
Posts: 3
Likes: 0
2007 R500
Welp, turned out to be the rear SAM module after all. The dealer tested the output directly at the module, and while it shows 10V or so with nothing connected, it goes to 0V as soon as a load is placed on the turn signal pin.
$1000 to fix a turn signal!
$1000 to fix a turn signal!
Out Of Control!!
Joined: Apr 2019
Posts: 11,921
Likes: 6,775
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
$1000 part + labor ... ouch! At least you know it was fixed with a new part that was going to fail for something else anyway.
It's sort of amazing how MB has engineered good parts into perfect junk like the aluminium intake plenum resonator that need to be replaced and still charge top price
It's sort of amazing how MB has engineered good parts into perfect junk like the aluminium intake plenum resonator that need to be replaced and still charge top price
