ML350 Trailer Hitch and Wiring Harness Question
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ML350
ML350 Trailer Hitch and Wiring Harness Question
I am considering getting a trailer hitch for my wife’s car. Per U-Haul, I understand the trailer wiring harness is special for her car. She has a 2009 ML350. I will install the hitch myself. What is so special about the wiring harness and installation? I received a quote from the dealer only selling the hitch, harness and installation - no breakouts. I was surprised how much they want...
Thanks in advance.
Thanks in advance.
Member
Joined: Mar 2008
Posts: 79
Likes: 10
From: San Diego, CA or Sequim Washington USA
'95-E320 COUPE, 2000 SL500, 2002 ML320
Just a caution about anyone touching any wiring on your ML. Not everyone is aware of or has experience installing their own equipment on a Mercedes, even U-Hall. They were not aware of the adapter plug for the factory installed tow package with LEDs. Before I rented a trailer I went in to confirm they carried the plug adapter that worked with my LEDs they said they did but when I went to pick up the trailer and it didn't work their first instinct was to trouble shoot the wire connections and pull it a part. I had to prevent them touching anything.
The guys at San Diego trailer knew what I needed and carried the adapter in stock and it worked without a hitch ( or in this case with).
The guys at San Diego trailer knew what I needed and carried the adapter in stock and it worked without a hitch ( or in this case with).
Out Of Control!!
Joined: Aug 2010
Posts: 12,516
Likes: 628
From: Charlotte NC area
2019 WS222 S450 4-Matic / 2007 W211 E350 4Matic (Sold) / 2008 X164 GL320 CDI
The red light up adapter from U-Haul ($13) worked fine on my '08 GL (Factory tow package).
The ML and GL wiring is (or should be) the same.
The ML and GL wiring is (or should be) the same.
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Joined: Sep 2021
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MB ML350 164
Trailer Hitch wiring
I have an ML 350 V6 Build date 11/06.
I have purchase the Hitch harness from the Benze dealer here in Australia, it is the correct one for my Vin #.
When I went to fitting it there is no receptical for the over centre plug to connect to the SAM unit there are the places but there is a plastic cover over the hole and it has nothing under it.
The dealer tells me that my car was not built to tow a trailer.
.
Is it possible to buy a SAM to replace the one I have or will there be other connective issues?
Is it possible to buy an alternative loom /wiring system to enable a trailer to be attached ,I dont need trailer brakes.
Thanks
I have purchase the Hitch harness from the Benze dealer here in Australia, it is the correct one for my Vin #.
When I went to fitting it there is no receptical for the over centre plug to connect to the SAM unit there are the places but there is a plastic cover over the hole and it has nothing under it.
The dealer tells me that my car was not built to tow a trailer.
.
Is it possible to buy a SAM to replace the one I have or will there be other connective issues?
Is it possible to buy an alternative loom /wiring system to enable a trailer to be attached ,I dont need trailer brakes.
Thanks
Last edited by Barney @21; Dec 3, 2021 at 12:00 AM.
MBWorld Fanatic!
Joined: Oct 2011
Posts: 7,107
Likes: 765
From: Bronx, N.Y.
2002 ML 320 & 2006 ML500
You should always ask questions before purchasing parts. To retrofit the Trailer hitch it requires the replacement of the rear SAM (as you know) and a special Cooling Fan.
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Joined: Sep 2021
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MB ML350 164
Thanks for your info.
I did actually try to get all the info , even the dealer said they had not come across this exact situation before. They suggested just changing the SAM may not work as the replacement may not talk to the rest of the sytem?? I was hoping to just pick up the affected circuits ( Tail /Stop / Blinkers) at the fuse ???. My car has coventional globes , Trailer has LED , my thoughts were that the SAM would not register the additional lights as the current draw would be so small??
Thanks again for your input.
I did actually try to get all the info , even the dealer said they had not come across this exact situation before. They suggested just changing the SAM may not work as the replacement may not talk to the rest of the sytem?? I was hoping to just pick up the affected circuits ( Tail /Stop / Blinkers) at the fuse ???. My car has coventional globes , Trailer has LED , my thoughts were that the SAM would not register the additional lights as the current draw would be so small??
Thanks again for your input.
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Super Member
Joined: Nov 2017
Posts: 558
Likes: 114
From: San Francisco Bay Area
2006 R500
Thanks for your info.
I did actually try to get all the info , even the dealer said they had not come across this exact situation before. They suggested just changing the SAM may not work as the replacement may not talk to the rest of the sytem?? I was hoping to just pick up the affected circuits ( Tail /Stop / Blinkers) at the fuse ???. My car has coventional globes , Trailer has LED , my thoughts were that the SAM would not register the additional lights as the current draw would be so small??
Thanks again for your input.
I did actually try to get all the info , even the dealer said they had not come across this exact situation before. They suggested just changing the SAM may not work as the replacement may not talk to the rest of the sytem?? I was hoping to just pick up the affected circuits ( Tail /Stop / Blinkers) at the fuse ???. My car has coventional globes , Trailer has LED , my thoughts were that the SAM would not register the additional lights as the current draw would be so small??
Thanks again for your input.
As for the LED trailer lights, what will most likely happen is that you get a warning that the trailer light is out and hyperflashing. To counteract that, you can get an adapter that cancels the error. Similar to this:
Last edited by Tsumi; Dec 7, 2021 at 12:30 PM.
MBWorld Fanatic!
Joined: Sep 2005
Posts: 6,192
Likes: 242
From: Albuquerque
'10 CL550, '12 GL550
I am considering getting a trailer hitch for my wife’s car. Per U-Haul, I understand the trailer wiring harness is special for her car. She has a 2009 ML350. I will install the hitch myself. What is so special about the wiring harness and installation? I received a quote from the dealer only selling the hitch, harness and installation - no breakouts. I was surprised how much they want...
Thanks in advance.
Thanks in advance.
one doesn’t “tap in” anywhere on a CAN bus.
Super Member
Joined: Nov 2017
Posts: 558
Likes: 114
From: San Francisco Bay Area
2006 R500
what is “special” is that this vehicle has a CAN bus electrical system rather than a conventional electrical system. This means everything is computer controlled. For example single filament bulbs are used as both (same bulb) tail and brake lights. Computer sends 5v for tail, increases to 12v for brake. Can detect burned out bulb and substitute another.
one doesn’t “tap in” anywhere on a CAN bus.
one doesn’t “tap in” anywhere on a CAN bus.
Junior Member
Joined: Jan 2022
Posts: 67
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Mercedes ML350 Bluetec 2012
Maj. Dundee
The WIS for the OEM hitch that you posted on ( 12-03-2021 ) was very enlightening, but I am trying to add a hitch to my 2012 ML350 BT, which is a 166, how would I get copies of the WIS for it. It also looks like there may be an additional wire harness that I may need, was looking at ECS TUNING web site which sells a complete hitch kit for my vehicles and it is show an extra wire bundle that I do not have. I will get the mechanical completed, but would also like to the electrical element completed as well?
Bob Massmann
2012 ML350 BT
The WIS for the OEM hitch that you posted on ( 12-03-2021 ) was very enlightening, but I am trying to add a hitch to my 2012 ML350 BT, which is a 166, how would I get copies of the WIS for it. It also looks like there may be an additional wire harness that I may need, was looking at ECS TUNING web site which sells a complete hitch kit for my vehicles and it is show an extra wire bundle that I do not have. I will get the mechanical completed, but would also like to the electrical element completed as well?
Bob Massmann
2012 ML350 BT
MBWorld Fanatic!
Joined: Oct 2011
Posts: 7,107
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From: Bronx, N.Y.
2002 ML 320 & 2006 ML500
Maj. Dundee
The WIS for the OEM hitch that you posted on ( 12-03-2021 ) was very enlightening, but I am trying to add a hitch to my 2012 ML350 BT, which is a 166, how would I get copies of the WIS for it. It also looks like there may be an additional wire harness that I may need, was looking at ECS TUNING web site which sells a complete hitch kit for my vehicles and it is show an extra wire bundle that I do not have. I will get the mechanical completed, but would also like to the electrical element completed as well?
Bob Massmann
2012 ML350 BT
The WIS for the OEM hitch that you posted on ( 12-03-2021 ) was very enlightening, but I am trying to add a hitch to my 2012 ML350 BT, which is a 166, how would I get copies of the WIS for it. It also looks like there may be an additional wire harness that I may need, was looking at ECS TUNING web site which sells a complete hitch kit for my vehicles and it is show an extra wire bundle that I do not have. I will get the mechanical completed, but would also like to the electrical element completed as well?
Bob Massmann
2012 ML350 BT
Junior Member
Joined: Jan 2022
Posts: 67
Likes: 18
Mercedes ML350 Bluetec 2012
Maj. Dundee,
Thank you for the work instruction. It is really very involved isn't it. As I traded my only car with a trailer hitch and would prefer to use the ML for my trailer hauler, at this point I am sort of committed. I have most of the items to complete the job, but still need to find the second wire harness that connects to the cars electrical systems. I did find the trailer control module is still available through MB maybe the cable assembly is available too? I have found an alternate harness that only requires inductive pickups being added, but if I want to add a heavier trailer, I sure would like to take advantage of the car making adjustments based on what connected to it.
Bob Massmann
2012 ML350 BT
Thank you for the work instruction. It is really very involved isn't it. As I traded my only car with a trailer hitch and would prefer to use the ML for my trailer hauler, at this point I am sort of committed. I have most of the items to complete the job, but still need to find the second wire harness that connects to the cars electrical systems. I did find the trailer control module is still available through MB maybe the cable assembly is available too? I have found an alternate harness that only requires inductive pickups being added, but if I want to add a heavier trailer, I sure would like to take advantage of the car making adjustments based on what connected to it.
Bob Massmann
2012 ML350 BT
Last edited by rmassmann; Apr 20, 2022 at 02:29 PM. Reason: added signature
MBWorld Fanatic!
Joined: Sep 2005
Posts: 6,192
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From: Albuquerque
'10 CL550, '12 GL550
If the vehicle has Airmatic, automatic suspension lowering at highway speed will not occur if trailer is detected.
Status of trailer lighting will be monitored and messages appear on dash if a bulb is defective.
Last edited by lkchris; Apr 20, 2022 at 09:11 PM.
Super Member
Joined: Nov 2017
Posts: 558
Likes: 114
From: San Francisco Bay Area
2006 R500
Our R500 got 12-13 mpg pulling a 23' boat. That's the same mileage our 5.7 Ram MegaCab gets empty.
