W2KOP

Hey Everyone, this is my first post, on an old thread. I just purchased an aftermarket trailer hitch from Curt Hitches. I need to purchase the OEM harness and have my local MB dealer install it. The local parts department is telling me that the harness only comes with the complete trailer package. Has anyone who has installed an aftermarket hitch purchased the OEM harness?, and if so, can you supply me with the part number. Or has anyone installed an aftermarket harness? and does this void the warrantee? Thanks, Ken

NYCGLK

i can only speak for those with the factory hitch, and I think the harness is part of the assembley, so don't think OEM harness can be used with aftermarket hitch. Can just get aftermarket harness i guess.

Birel186

I'm on the same boat, looking to install a hitch and harness to tow my boat. Found this so far:
http://www.etrailer.com/Vehicle-Wiri...eid=2010301717

http://www.etrailer.com/t1-2010_Merc...nz_G-Class.htm

MilesBFree

I would suggest more research to see if it is possible to get a plug-in harness, whether factory or aftermarket.

The last thing you want to do is have some moron at a local hitch shop cut into the installed harness and slice in connections to the taillights and turn signal lights, and then duct tape the whole mess up.

I would have hoped MB designed the main rear harness to accept a plug-in trailer harness, as opposed to 2 separate harnesses, one for factory trailer hitch and one for without. It would not make sense for MB to need to produce 2 separate harmesses, but you never know.

I would think MB would sell the trailer hitch harness separately, since I can think of a number of scenarios that would need this to be available separately from the hitch, e.g.- wiring short, small fire, etc., that would burn the wiring but not the steel hitch.

Ruination Fan

Just another FYI, with the dealer install....you get a higher output cooling fan with the kit. Apparently MB wants the extra cooling ability when towing, just another heads up for those on the fence.

Birel186

My brother did it to my moms 328i so he could tow his dirt bike. Car never caught fire. It's not rocket science, the cables splice into a few wires; not a massive wiring harness.

And if your car is a lease, even more reason to. From what i've read, the only way to get the factory harness is to buy the hitch. The hitch is like $1200, and the dealer charges another $1500-$2000 to install everything. Yea, OK! Sorry I'll go with aftermarket.

MilesBFree

It's not rocket science, but by cutting wires you introduce potential failure points where you are cutting, splicing, and soldering or crimping the wires back together.

This may void the warranty on the wiring, or at the very least cause the dealer to hassle you if you ever had an electrical issue you asked them to fix under warranty. It is possible that you could cause issues in soldering, but even if not the dealer may claim you did.

That said, I agree that that should be pretty straightforward.

For me personally, I would wait to cut into the wiring harness until my warranty was up.

Also, as I pointed out, you should hopefully be able to find an aftermarket trailer harness that plugs directly into the factory rear harness. So that should be much cheaper than factory as you pointed out.

Also thanks to Ruination for pointing out the upgraded fan.

MilesBFree

Saw this in the manual:

============================
The vehicle is prewired to accept the sevenwire harness included in the Mercedes-Benz
approved trailer hitch receiver kit.

A four-pole conversion plug is available from your authorized Mercedes-Benz
Center as a spare part.

For further information, contact an authorized Mercedes-Benz Center.
============================

Has anyone ordered the harness or plug?

MilesBFree

Found this write-up on the '08 ML, which may be similar enough to the GLK. It has some interesting info on wiring, voltage, etc. Explains why you need a 7-wire harness.

http://www.benzworld.org/forums/w164...trailer-2.html

2Quick

The 7 wire plug is only on the factory installed hitch. My dealer told me they did not understand why Mercedes did not include the plug on ALL vehcles, but want to charge 2400 bucks to add it. I did the hitch for 215, the wiring for 45, and bought a trailer for 500 bucks. My total with tax, tags, and title was 900 for it all including my new trailer. DO IT YOURSELF!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Ruination Fan

The MB kit comes with a completely new impact strip(metal bumper behind the bumper skin) and also includes re-inforcements for the frame rails. It also includes a new cooling fan and triming for the bumper for trailer hitch. Its not like some of the kits that i have seen installed where they have bolt through the spare wheel area with a brace connected for support. Just so everyone knows that most of the cost is parts, and does take a bit more than four holes and connect wires.

MilesBFree

Ruination Fan, that makes a lot of sense, thanks for posting.

No one would ever buy the M-B hitch when they know they can go to Uhaul or other local shops and get a hitch for around $300 installed, or do it themselves for less.

It is not like a trailer hitch is all that glamorous and you think to yourself, zOMG* I NEED THE MB HITCH!!! * = the z was intentional

M-B might be able to charge premium pricing on some accessories such as wheels that add pizzazz and enable wider / lower profile / better tires.

But not a trailer hitch.

Ruination Fan

Without a doubt, just want people to know that more than four bolts and some splicing is what is involved with the install for the MB hitch.

MilesBFree

Not sure if this will help anyone, but just came across it while looking at another wiring question. This shows where the "trailer connection unit" is located. See pages 76 and 77:

http://www.theworkshopmb.com/GLKIntroduction2010.pdf

Has anyone that's added the wiring harness tapped into this unit?

bigmaho

So I went to my local M/B dealer and asked about a trailer hitch and they pretty much told me to go third party. They no longer offer a class 3 hitch for the GLK250, and what they do offer is $675 for the hitch and $1800 for the install. They recommended Curt or Reese for a class 3 hitch. I was hoping to get a built in 7 pin connector so it looks fairly professional instead of the dangling 4 pin flat I see on most DIY jobs. Keep trying to find official Mercedes info on line, But can't find anything pertaining to trailer hitches. Guess I'll have my local guy install the Curt. Never had so much trouble getting a hitch installed before!