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Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4814
Experience:  15 years master certified 100% fix rate and have access to factory radio codes, wiring, and instructions.
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I want to install the relay module lights on my

Customer Question

I want to install the relay module for trailer lights on my 2013 ML350. Where is the best place to connect into the tail, turn, stop and reverse wires and what colors should I be looking for? Can I get a wiring diagram and photo of the location? Send info to **********@yahoo.com
JA: Sometimes things that you think will be really complicated end up being easy to fix with a Mercedes. The Mercedes Mechanic I'm going to connect you with knows all the tricks and shortcuts. Are you hoping to fix this yourself?
Customer: Yes
JA: Great! What have you tried so far?
Customer: Nothing yet, I want to do it right the first time.
JA: Is there anything else the Mercedes Mechanic should be aware of about your Mercedes?
Customer: No
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Submitted: 1 year ago.
Category: Mercedes
Expert:  Pete replied 1 year ago.
Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay. Does your vehicle have the factory hitch installed and factory wiring already installed leading to the trailer hitch? Let me know,thanks Pete.
Customer: replied 1 year ago.
No I do not have a hitch or the wiring loom for a trailer hook up. I do not anticipate any problems installing the hitch. However the wiring is a different can of worms. I have purchased the solid state relay, necessary to tap into the Mercedes wiring however I do not have good instructions on where I should tap into. I am aware of the patches in the side panels of the trunk area that I can pop open and interview the word both left and right sides. It appears that most of the wiring is on the right side however there is a smaller Loom of also available on the left side that I can get to. My main question is which of these looms should I look for and what color wire should I be looking for for the brake, tail,turn and back up lights. The backup light wiring issue of particular interest to me as my trailer has surge brakes and the signal from the backup lights needs to be applied to the trailer brake release for the surge brakes.
Expert:  Pete replied 1 year ago.
O.k.,unfortunately like you say this is a can of worms. Your vehicles Rear SAM control unit controls the trailer lights.This is the component located under the rear fuse panel in the right rear cargo area.It has a dummy electrical plug in it with no terminals.The SAM has to be replaced with one for the trailer provision,then at the same time the Sam trailer harness is plugged into the non dummy connection of the new SAM and ran through the holes in the floor to the hitch.The SAM as well as other ECU's in your model also have to be coded with a dealers SDS machine to then work the trailer lights.I have had to do this on several of these before.If your SAM has the electrical plug on it (it will be an open plug with terminals in it and no connector in it) then you can obtain the harness from a dealer and install it and have them code the SAM to work the trailer lights. There isnt any wiring you can tap into to make the lights work on this model here unfortunately as these are all data wires that if anything is tapped into will set off a fault disabling lights. If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.Thanks Pete
Customer: replied 1 year ago.
Thank you, ***** ***** be up to 2 weeks before I can get actually get around to this project. I will give you a rating and reply at that time. Is this okay?
Expert:  Pete replied 1 year ago.
Your welcome.You can rate at any time if you like and reply as much as needed any time as well.Thanks Pete
Customer: replied 1 year ago.
Can you better describe the location of the fuse box you are referring to? I did find one located under the rear seat. Is this the one you are referring to?
Expert:  Pete replied 1 year ago.
The rear fuse panel is in the passenger rear cargo area as well as the rear sam. https://www.dropbox.com/s/jkhqtl36s50ln51/fb-04-24.jpg?dl=0 The sam will look like this here and if you see the far connector alone by itself in this image this will either be a dummy connector with no pins in it with the sam needing replaced or it will have the pins in it and the wiring will need obtained and the sam programmed by a dealer. https://www.dropbox.com/s/2kilvdhvwm2uh3t/rsam-04-24.jpg?dl=0
Customer: replied 1 year ago.
Pete, The photo's you show must be for a different model year as the interior shot does not show the access openings on each of the interior side panels. Also the SAM box is accessed by flipping the lower section of the back seat forward. It does not look like the one you pictured. I have photo's but am unsure how to attach to this reply. Is there a email address I can send them to?
Expert:  Pete replied 1 year ago.
The pictures I showed were general pictures I had located on this model here and after double checking you are correct where the sam is located.On this year model here you have a trailer recognition control unit that the wiring comes from.This is tied into the sam and other control modules as well.Since your model did not come with trailer lights this will have to be installed with the trailer harness.You will need to check with a dealer to see if they have a retrofit kit for this here as most will have for your model.The module and harness is then installed and then the dealer will need to code/program the control unit as well as others to allow proper operation of the sam and the trailer control module.I apologize for the above info as my first part of info was showing it as the old style with the rear sam controlling the trailer wiring and in this case this is not what controls it.A dealer should have a retro fit kit for the wiring and control unit. Thanks Pete
Customer: replied 1 year ago.
Pete, I have purchased a TEKONSHA Modulite HD Protector with Backup (model 119177) which I am assured will NOT interfere with the Mercedes wiring or circuit functions. This adapter works by sensing the voltage in the wiring and does not impose any additional load on the wire it is attached to. My question to you is, how do I locate the appropriate wires for each function ie brake, turn, taillight and backup? Also in my last memo I asked how I can send you pictures of the vehicle I am working on.
Expert:  Pete replied 1 year ago.
I apologize. You can usually upload them using the paper clip or tree icon if you see one to use.If you do not let me know. Thanks Pete
Customer: replied 1 year ago.
I don't see a paper clip or tree icon. If I had a Email address I could send the pictures, that would help. Also, please can you what wire colors to look for and exactly where to look for them? I have been checking with a computer safe test probe and think I may have found a couple of them. I am particularly at a loss when it comes to locating the backup lights which are also LED style lamps.
Expert:  Pete replied 1 year ago.
Unfortunately after looking through my info on this here I dont show or see the wire color info on this myself.I will open your question up for others here to see if someone else can assist further on this as there may be others here that may have more info on what to check or do with this issue.I hope you can get this resolved with ease.No need to reply to my last post here unless it is a last resort as it will keep your question locked to me and others will not be able to view it.If you feel you want to continue to work with me on this feel free to reply at any time but keep in mind in some cases it can be difficult to fully diagnose or help repair this without seeing your vehicle.Thanks Pete
Expert:  Lou P. master tech replied 1 year ago.
Hello, different expert here, Lou P. i can assist, first off i read through your previous chat with pete. please do not go poking random wires for power as you can create a headache for yourself, i can assist with the wiring . we can use the wiring at the taillight housings most likely. are you still wanting help with this?
Customer: replied 1 year ago.
Hi Lou P, looking forward to working with you. Yes I still want help this. I have purchased a low current draw probe that should be safe too probe the wires with. I especially need to find the backup light wiring as this will be necessary to signal the low current demand relay. This signal is then sent on to the brake release on the surge brakes on the trailer.
Expert:  Lou P. master tech replied 1 year ago.
ok let me check the diagrams. be back soon and if not i will get back on tonight with the info i will respond either way. Lou P.
Customer: replied 1 year ago.
Thanks
Expert:  Lou P. master tech replied 1 year ago.
OK so access the connector to the right taillight assembly, right as in passenger side. the wires you need are pin 2 green wire with blue stripe (taillight bulb )pin 3 violet with black stripe (turn signal light )pin 4 green with black stripe (stop light bulb)pin 1 brown (ground if needed)on the tailgate is the reverse light so you will have to access the wiring from the rear sam for this one , white wire blue stripe i will get you the connector that the wire is in.
Expert:  Lou P. master tech replied 1 year ago.
ok so there are 2 bigger 48 pin connectors that are identical, you need the one that pin 5 is the color of wire i stated, white wire with blue stripe. that is your reverse light output. hope this helps. let me clarify its not the REAR sam, or REAR control module, its the SAM module, here is a picture of the location.
Expert:  Lou P. master tech replied 1 year ago.
its in the right front a pillar area so you are gonna have to run the wire the length to wherever you are gonna mount the unit to. hope this helps.
Customer: replied 1 year ago.
Lou P. You say pin 3 is turn signal, you do not say if it is right or left, I will need both R & L. If Pin 3 is right, do I go to Left side for left turn signal? Remember this is a LED taillight assembly the brake and turn signals are separate wires. I suggest you go to Tekonsha website; Tekonsha.com and enter part # ***** for more details on their relay. Also they have a very good Tech support #(###) ###-####(make sure you get tech support not customer service) The Telonsha controller has 5 inputs and outputs, 2 separate for L & R turn, 1 for taillight, 1 for brake and 1 for backup. It also has it's own positive and negative inputs. I hope this helps you better understand the vehicle I am working on. If you could tell me where to send photos, I can do that as well. I have tried using the "Add files" link next to the send button but can't make any files attach.
I have a circuit tester for use on LED circuits that only draws 21ma on a 12vdc source.
Customer: replied 1 year ago.
PS I took cover off passenger R front panel but it does not look like the picture you sent me.
Expert:  Lou P. master tech replied 1 year ago.
first off did you locate the wires i explained at the right taillight?
Customer: replied 1 year ago.
I don't trust my notes as I took them early on, but the wire going into the right assembly that caused my probe to blink with turn signal on was the green w/black stripe and the solid non blinking wire was grey, I never found the R brake but the bulb that lights up when brake is applied is a non-led regular incandescent bulb. I will not be able to work on my car again until Wed afternoon so you should have time to research this situation further.
Expert:  Lou P. master tech replied 1 year ago.
ok what is your vin, .also i need you to tell me the color wires in both left and right taillight assemblies so i can make sure they match up. we are going to use the turn signals from both lamps yes, but only need the light signals from one lamp. the module picture was shown with the heater box removed, the module is tucked up between the heater box and the sheet metal, can you verify if it is there or not. that is what the wiring diagram is showing me hence the picture i sent you.
Customer: replied 1 year ago.
VIN. 4JGDA5HB2DA149538 RIGHT TAIL, PLUG #1 BROWN, GREEN & BLACK STRIPE, PURPLE & BLACK STRIPE,
GREY & BLUE STRIPE. PLUG #2 BLACK, YELLOW (connected to non LED light)
LEFT TAIL, PLUG #1 BROWN, GREY & BLACK STRIPE, WHITE & BLACK STRIPE, SOLID BLACK. PLUG #2 BLACK, YELLOW (connected to non LED light)
Customer: replied 1 year ago.
I have yet to look further behind the kick panel for the control module, will try to do tomorrow.
Customer: replied 1 year ago.
Lou, I see the front control module on the A pillar base just above the kick panel as you pictured. Is there a wire in one of the looms that come down into the kick panel area that I can access or is there access this wire somewhere along it's route to the rear of the vehicle. I don't want to go sticking my probe into just any wire until I am positive I am selecting the right wire and will not cause any damage.
Expert:  Lou P. master tech replied 1 year ago.
the wire color i told you about is the wire we need to access, i would start by pulling down the module. dont risk finding it in the loom the module will come down easily. i will go over your wiring you reported back.
Customer: replied 1 year ago.
Getting to the module appears to be difficult, can you guide me thru the necessary steps? Do I have to take out the glove box and it's liner? How about the under dash cover?
Expert:  Lou P. master tech replied 1 year ago.
sorry for the delay. i will get instructions for you now
Expert:  Lou P. master tech replied 1 year ago.
here are the instructions , i have a problem, our wiring does not match up. we are close but its not 100% and i cant find why. i will have to opt out.
Customer: replied 1 year ago.
Lou, Got your last message, what do you mean "opt out" are you saying you can't help me any more? I don't plan on working on this again until next week, maybe you can give it another try. I really only need to know which wire in the forward SAM I need to connect with for the backup signal, I can probably figure out which wires to tap into for the brake, turn and tail lights at the tail light assembly. Please let me know if I need to request another technician.