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Red 1987 560SL, Grey 2010 ML350 (gas), Grey 2010 E350
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Discussion Starter #1
After failing to find a used trailer hitch for my 2002 ML320 online or at the local salvage yards, I spotted a 1999 ML350 with a hitch installed in the parking lot of the local Barnes & Noble bookstore. It didn't look like it had been used recently. I left a note on the windshield offering to buy the hitch. A couple of hours later, the owner called me up and we agreed on a price. How's that for Blind-Dumb-Luck?

Anyway, he drove over to my house today and I spent two hours removing the hitch and all the parts. See the pic below. I've got everything except one spacer and bolt/nut for one of the braces. Guess I'll be able to find one at the "Bolt Store"?

I'll attempt to install next weekend. Removing it was not too complicated, just took a lot of ass and muscle to break those bolts free. And getting the plug to disconnect from the wiring harness was a pain in the knuckles. The little side compartment opening didn't give me much room to move my hands around the connector.

Does anyone have some good advice or experience installing an OEM hitch? My ML320 is a 2002 model - slightly different from the 1999 model I got the hitch from. Mainly concerned about the wiring harness. Any advice would be Appreciated!!!
-Brian
 

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1990 190E 2.6,.... 1998 ML320, 2005 ML500SE
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3,115 Posts

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Red 1987 560SL, Grey 2010 ML350 (gas), Grey 2010 E350
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228 Posts
Discussion Starter #3
MIke,

Yeah, my harness doesn't have a "Y" at the end that connects to the vehicle harness. Is my harness an older model? It came from a 1999 ML. What is the "isolation module", what does it do, and can I add it to my harness? Thanks!
Brian
 

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2001 ML 55AMG
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1,158 Posts
Make sure you don't use the Micro encapsulated hexagon screws you removed. They can only be used 1 time. You will need to purchase new screws.
 

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Red 1987 560SL, Grey 2010 ML350 (gas), Grey 2010 E350
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228 Posts
Discussion Starter #5
Make sure you don't use the Micro encapsulated hexagon screws you removed. They can only be used 1 time. You will need to purchase new screws.
Which ones are the Micro encapsulated hexagon screws? Thanks!

Brian
 

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1990 190E 2.6,.... 1998 ML320, 2005 ML500SE
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3,115 Posts
MIke,

Yeah, my harness doesn't have a "Y" at the end that connects to the vehicle harness. Is my harness an older model? It came from a 1999 ML. What is the "isolation module", what does it do, and can I add it to my harness? Thanks!
Brian
All W163 ML"s (1998 - 2005) came with an isolation module in the wiring harness. Your harness does look like the OE harness BUT the electrical tape indicates that the harness has been hacked and the module has been bypassed. Not good. The trailer lights are powered directly by the ML's lighting system (with the above harness) possibly overloading the ML's wiring.

The Isolation module is powered by a separate fuse, (F18 - 25A) (see above posts I provided for details). It only uses a 12V signal, at no load, to operate and power the trailer lights. It also acts as a converter from the current lighting system to a trailer's 4 wire system (combination turn / brake lights). It also completely isolates the trailer wiring from the ML's wiring so any problem with the trailer wiring, like a short, will not damage the ML's wiring.

I recommend seeing the posts above and add the module shown. Your wiring harness / Plugs will be a good start.

Good Luck,
Mike

[EDDIT / addition] The "Micro encapsulated hexagon screws" are the 4 Bolts shown on the far left in your picture above. The Bolts that mount the Hitch Receiver to the bumper. (fyi, I reused mine with Locktite thread sealer since I only tow a small utility trailer)
The screw specs are M 14x1.5x55-10.9. Torque spec for these screws is 118 ftlb (160 Nm)
 

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2006 ML500 2002 ML320
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Micro-encapsulation bolts only refers to the lock tightening agent used, not the bolt itself, per se.

Special lock tight is applied to certain bolts throughout the veh. which requires lock tight and it is applied to those bolts way before assembly for the simple fact that it wouldn't be cost effective on the assembly line. And it does not activate itself until the bolt has reached its required torque setting.

It also requires less setting time as opposed to the regular liquid lock tight, which is longer. Therefore, the bolt can be used again as long as a quality liquid lock tight is used on the same area designated at the plant.

These bolts are not to be confused with torque to yield bolts which must be replaced after being removed.
 

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