2008 ML350 tow hitch question
11-04-2011, 10:25 AM
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2008 ML350 4matic
2008 ML350 tow hitch question
Just purchased CPO 2008 ML350 and looking for recommendations for a tow hitch other than MB branded.
Dealer quoted $2,300 for parts & labor. They mentioned a 4 day install due to rear bumper/undercarriage modification. Worried that after-market company, no matter how good, will not install correctly. Thoughts/experience? Hoping to find an after-market option that is as hidden or fits as well. Thanks!
Dealer quoted $2,300 for parts & labor. They mentioned a 4 day install due to rear bumper/undercarriage modification. Worried that after-market company, no matter how good, will not install correctly. Thoughts/experience? Hoping to find an after-market option that is as hidden or fits as well. Thanks!
11-04-2011, 01:32 PM
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2011 GL450, '06 R500 traded, '08 ML350 sold
If you do a search you will find a lot of info on the subject. Although you can find an aftermarket hitch quite inexpensively ($120 or so) you will still need the OEM electronics for lights, and the traction control system.
IMO if you only need it for a bike rack and such then skip the electronic harness.
IMO if you only need it for a bike rack and such then skip the electronic harness.
11-04-2011, 04:07 PM
#3
What's the purpose for the hitch? If you want to tow something heavy(4000lb+)you need oem hitch. if you just want to attach bike rack or occassional lightweight towing you can go aftermarket for around $250.
I had 08 ml without hitch and bought aftermarket hitch and wiring kit for under $300 on eBay but never got to install them. I need to tow my Z every once in awhile so I traded it for a new o e with oem hitch.
I had 08 ml without hitch and bought aftermarket hitch and wiring kit for under $300 on eBay but never got to install them. I need to tow my Z every once in awhile so I traded it for a new o e with oem hitch.
11-04-2011, 06:32 PM
#5
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If you are going to tow a lot, then spring for the dealer option. The rear SAM needs to know the hitch is there to activate the trailer stability feature, (or something like that) and the mounting and performance will be warranted by Mercedes.
Make sure the hitch has the proper welds as there was a recall some years back because the manufacture missed a spot.
Make sure the hitch has the proper welds as there was a recall some years back because the manufacture missed a spot.
11-05-2011, 10:01 AM
#6
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For my 2008 ML350 and my modest trailering needs, I went with the aftermarket approach and installed the Curt trailer hitch (13342) which claims a load limit of 3500lbs. I like the fit and glossy finish on the hitch. It takes two people and a couple hours to install.
For the wiring, I got off to a bad start with the Curt 56200 which is also available as the Curt 59200 kit. The "problem" is that my lights aren't set up with pulse modulated control for the brake lights.
In the housing, from top to bottom, my 2008 ML350 has:
1. an incandescent brake light in the top layer
2a. an incandescent turn signal in the "outside" middle layer,
2b. an incandescent back-up light in the "inside" middle layer,
3a. LED running lights on the "outside" bottom layer,
3b. LED running lights on the "inside" bottom layer which also serve as the "rear fog" lamps (depending on pulse width modulation).
I checked voltages and eventually hooked up the oscilloscope (yes I am a geek). The top and middle layers are simple 12 volt on/off arrangements.
The bottom layer (LEDs) is very different. The running lights (both the "inside" and "outside") are "on" when a 12 volt, pulse width modulated signal is present. This square-wave signal seems to be on for 1 ms and off for 2.5 ms. When the fog light is "on" there is a solid 12 signal on the "inside" section.
So, the PWM signal for the running lights is modulated against the fog light, but only for one of the lower segments.
The running lights are not modulated against the brake lights. The Curt 56200/59200 expects the tail lights and brake lights to share a circuit. That's not what the 2008 ML350 is doing.
I contacted Curt and they told me that the 56200 was clearly not the right module for this car and that I should look into their 56146. An internet search showed that others have been successful with the 56146 (or kit version 59146) as well as with the Modulite(aka TowReady) 119190 (or kit version 119191).
Electrically, these two units are identical. Ultimately I went with the Modulite because they claimed more current capability. (I bought the 119191 kit for the convenience of the wire, fuse holder, the Scotchloks and the grounding screws.)
The rest of the project was smooth.
Just to document what else I've learned, the wire colors in my harness for the driver's side (left) bulb housing are as follows:
Top
Brown: Ground
Black: Left Turn (12V)
Pink: Brake (12V)
White AND white w/ black: Reverse (12V)
White w/ green: Running (30% duty cycle)
Grey w/ black: Running (30% duty cycle) and Rear Fog (100% duty cycle)
Bottom
The turn signal in the passenger side housing is a green wire with a black stripe.
Using the fuse holder included in the kit, I connected to power at the enormous, exposed terminal on the fuse block on the passenger side in the rear of the car. I was surprised/pleased to find power so available at the rear of the car!
Since the SAM is not being tasked with any new duties, I find no "need" for an upgrade (see Note below).
So that's it. I do want to say that I didn't figure all this out on my own. I found a lot of help/guidance (and pictures) by searching the web. I'm simply documenting it here to inform others of a viable path.
(Note: I've read that to gain the full weight towing capability of the vehicle, you'll need the MB OEM hitch. I've also read that there may be advantages of upgrading a SAM which could result in improved handling of heavy trailers and integration of the wiring of the trailer into a SAM can be used as way of informing the car that there is a trailer attached. I chosen to not "worry" about these issues- if I find that I'm in need of towing a trailer over 3500lbs, I can upgrade to the OEM hitch and SAM(s) or to a different vehicle! - or rent for a couple days!)
I recognize that different people have different tolerances for risk and impact. I'm not saying that this path is ideal for everyone. Personally, I am aware of and willing to accept the risks associated with this sort of commercially available DIY project and use of the outcome for my needs. This path worked for me and I am comfortable with the process and outcome. If you feel that this path would take you outside your tolerance of risk, please don't follow.
For the wiring, I got off to a bad start with the Curt 56200 which is also available as the Curt 59200 kit. The "problem" is that my lights aren't set up with pulse modulated control for the brake lights.
In the housing, from top to bottom, my 2008 ML350 has:
1. an incandescent brake light in the top layer
2a. an incandescent turn signal in the "outside" middle layer,
2b. an incandescent back-up light in the "inside" middle layer,
3a. LED running lights on the "outside" bottom layer,
3b. LED running lights on the "inside" bottom layer which also serve as the "rear fog" lamps (depending on pulse width modulation).
I checked voltages and eventually hooked up the oscilloscope (yes I am a geek). The top and middle layers are simple 12 volt on/off arrangements.
The bottom layer (LEDs) is very different. The running lights (both the "inside" and "outside") are "on" when a 12 volt, pulse width modulated signal is present. This square-wave signal seems to be on for 1 ms and off for 2.5 ms. When the fog light is "on" there is a solid 12 signal on the "inside" section.
So, the PWM signal for the running lights is modulated against the fog light, but only for one of the lower segments.
The running lights are not modulated against the brake lights. The Curt 56200/59200 expects the tail lights and brake lights to share a circuit. That's not what the 2008 ML350 is doing.
I contacted Curt and they told me that the 56200 was clearly not the right module for this car and that I should look into their 56146. An internet search showed that others have been successful with the 56146 (or kit version 59146) as well as with the Modulite(aka TowReady) 119190 (or kit version 119191).
Electrically, these two units are identical. Ultimately I went with the Modulite because they claimed more current capability. (I bought the 119191 kit for the convenience of the wire, fuse holder, the Scotchloks and the grounding screws.)
The rest of the project was smooth.
Just to document what else I've learned, the wire colors in my harness for the driver's side (left) bulb housing are as follows:
Top
Brown: Ground
Black: Left Turn (12V)
Pink: Brake (12V)
White AND white w/ black: Reverse (12V)
White w/ green: Running (30% duty cycle)
Grey w/ black: Running (30% duty cycle) and Rear Fog (100% duty cycle)
Bottom
The turn signal in the passenger side housing is a green wire with a black stripe.
Using the fuse holder included in the kit, I connected to power at the enormous, exposed terminal on the fuse block on the passenger side in the rear of the car. I was surprised/pleased to find power so available at the rear of the car!
Since the SAM is not being tasked with any new duties, I find no "need" for an upgrade (see Note below).
So that's it. I do want to say that I didn't figure all this out on my own. I found a lot of help/guidance (and pictures) by searching the web. I'm simply documenting it here to inform others of a viable path.
(Note: I've read that to gain the full weight towing capability of the vehicle, you'll need the MB OEM hitch. I've also read that there may be advantages of upgrading a SAM which could result in improved handling of heavy trailers and integration of the wiring of the trailer into a SAM can be used as way of informing the car that there is a trailer attached. I chosen to not "worry" about these issues- if I find that I'm in need of towing a trailer over 3500lbs, I can upgrade to the OEM hitch and SAM(s) or to a different vehicle! - or rent for a couple days!)
I recognize that different people have different tolerances for risk and impact. I'm not saying that this path is ideal for everyone. Personally, I am aware of and willing to accept the risks associated with this sort of commercially available DIY project and use of the outcome for my needs. This path worked for me and I am comfortable with the process and outcome. If you feel that this path would take you outside your tolerance of risk, please don't follow.
11-07-2011, 09:22 AM
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2008 ML350 4matic
thanks to all for good insight and info! spent a lot of time this weekend on forums and parts sites and will report back on choice and success(or failure!) of final choice.
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08-11-2012, 11:41 PM
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Now there's the matter of electrics, which of course means a 3-wire to 2-wire power adapter.
