4th Mercedes, R-Class Trailer-Hitch Lament
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Joined: Aug 2013
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From: Deepinnaharta, Texas
2011 R-350, 2007 E-350
4th Mercedes, R-Class Trailer-Hitch Lament
Greetings:
Three days. That's how much time I'm into this Draw-Tite hitch installation including wiring for a brake controller and 7-pin socket.
This New-to-Me is my 4th M-B vehicle. Current other (wife's) ride is a 2007 E-350. Past owner 1999 C-230 and 1985 500 SL
The hitch weighs 45 pounds. Crawling underneath on short ramps in a 102-degree garage isn't my idea of fun. The lower rear fascia was easy to remove to see the position of the hitch better, but that's the only thing on this job that went well. Well, that and using a fish tape through the hood release cable grommet to gain access to the engine room from under the dash.
More to come, perhaps pics.
racetteguy,
AKA Wheelman-111
Three days. That's how much time I'm into this Draw-Tite hitch installation including wiring for a brake controller and 7-pin socket.
This New-to-Me is my 4th M-B vehicle. Current other (wife's) ride is a 2007 E-350. Past owner 1999 C-230 and 1985 500 SL
The hitch weighs 45 pounds. Crawling underneath on short ramps in a 102-degree garage isn't my idea of fun. The lower rear fascia was easy to remove to see the position of the hitch better, but that's the only thing on this job that went well. Well, that and using a fish tape through the hood release cable grommet to gain access to the engine room from under the dash.
More to come, perhaps pics.
racetteguy,
AKA Wheelman-111
Thread Starter
Newbie
Joined: Aug 2013
Posts: 7
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From: Deepinnaharta, Texas
2011 R-350, 2007 E-350
Other Hi-Lites
Greetings:
Connecting the light module ("splitter") proved more challenging than originally thought; Still haven't found which of the dozen wires inside the left tail-lamp cubby provides the current to the brake lamps. With the module connected to the flasher wires but NOT energized, brake pedal application by Ms. Wheelperson produced an interesting combination of lamp misbehavior. I'm assuming, unless someone can correct my error, that without power the brake application routes passively through some diodes in the module and illuminates the wrong bulbs(?)
Another observation concerning the rearmost hitch mounting beneath the bumper brace. Draw-Tite expects 53 pounds of torque on each of the 10mm through-bolt nuts. However applying much more than 40-45 pounds resulted in the bolt-head sinking a little into what appears to be an aluminum extrusion despite the large-ish cone washer beneath the bolt head. Sure hope their 3500-pound rating doesn't depend on presumed Steel from Stuttgart, because I dared not go beyond that value.
Finally, still seeking a viable "cold" brake switch wire somewhere beneath the bonnet. The brake lamp switch definitely does NOT reside beneath the dash, but hooking into that circuit has proven elusive as well
Connecting the light module ("splitter") proved more challenging than originally thought; Still haven't found which of the dozen wires inside the left tail-lamp cubby provides the current to the brake lamps. With the module connected to the flasher wires but NOT energized, brake pedal application by Ms. Wheelperson produced an interesting combination of lamp misbehavior. I'm assuming, unless someone can correct my error, that without power the brake application routes passively through some diodes in the module and illuminates the wrong bulbs(?)
Another observation concerning the rearmost hitch mounting beneath the bumper brace. Draw-Tite expects 53 pounds of torque on each of the 10mm through-bolt nuts. However applying much more than 40-45 pounds resulted in the bolt-head sinking a little into what appears to be an aluminum extrusion despite the large-ish cone washer beneath the bolt head. Sure hope their 3500-pound rating doesn't depend on presumed Steel from Stuttgart, because I dared not go beyond that value.
Finally, still seeking a viable "cold" brake switch wire somewhere beneath the bonnet. The brake lamp switch definitely does NOT reside beneath the dash, but hooking into that circuit has proven elusive as well
Thread Starter
Newbie
Joined: Aug 2013
Posts: 7
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From: Deepinnaharta, Texas
2011 R-350, 2007 E-350
Another observation concerning the rearmost hitch mounting beneath the bumper brace. Draw-Tite expects 53 pounds of torque on each of the 10mm through-bolt nuts. However applying much more than 40-45 pounds resulted in the bolt-head sinking a little into what appears to be an aluminum extrusion despite the large-ish cone washer beneath the bolt head. Sure hope their 3500-pound rating doesn't depend on presumed Steel from Stuttgart, because I dared not go beyond that value.
Finally, still seeking a viable "cold" brake switch wire somewhere beneath the bonnet. The brake lamp switch definitely does NOT reside beneath the dash, but hooking into that circuit has proven elusive as well[/QUOTE]
Finally, still seeking a viable "cold" brake switch wire somewhere beneath the bonnet. The brake lamp switch definitely does NOT reside beneath the dash, but hooking into that circuit has proven elusive as well[/QUOTE]
Thread Starter
Newbie
Joined: Aug 2013
Posts: 7
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From: Deepinnaharta, Texas
2011 R-350, 2007 E-350
Greetings:
I ran the wire from the rear brake lamp back to the under-dash brake controller because the actual hydraulic brake switch resides under the master cylinder where only trained Spider Monkeys can reach without significant disassembly. Seemed to work just fine.
I ran the wire from the rear brake lamp back to the under-dash brake controller because the actual hydraulic brake switch resides under the master cylinder where only trained Spider Monkeys can reach without significant disassembly. Seemed to work just fine.
Last edited by racetteguy; Aug 20, 2013 at 10:44 AM. Reason: Can't post from Galaxy...
Thread Starter
Newbie
Joined: Aug 2013
Posts: 7
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From: Deepinnaharta, Texas
2011 R-350, 2007 E-350
Successful Aftermarket Hitchings
Greetings:
The Draw-Tite hitch, 7-Pin connection and Tekonsha IQ brake controller are all working just fine. I have attempted to show a pic from the underside right showing the spare tire well belly pan cutaway. A good bit of plastic needed to be trimmed behind the bumper cover. Otherwise, it was not possible to reattach the fascia to the pan as the hitch pushed the painted under-bumper panel out much too far. Trimming concluded, cosmetic results to follow.
The Draw-Tite hitch, 7-Pin connection and Tekonsha IQ brake controller are all working just fine. I have attempted to show a pic from the underside right showing the spare tire well belly pan cutaway. A good bit of plastic needed to be trimmed behind the bumper cover. Otherwise, it was not possible to reattach the fascia to the pan as the hitch pushed the painted under-bumper panel out much too far. Trimming concluded, cosmetic results to follow.
Thread Starter
Newbie
Joined: Aug 2013
Posts: 7
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From: Deepinnaharta, Texas
2011 R-350, 2007 E-350
Hitch Conclusion
Greetings:
Raul of the U-Haul was tapped for 3 hours of his time to make the final connections. I did all the hardware installation. Tapping into the skinny Can-Bus wiring with ScotchClips proved risky. The U-Haul people had bulb-socket connectors that ensure a more positive contact and don't confuse the computer.
The Tekonsha IQ inertia-sensing proportional brake controller is a nice device. Very linear in operation, without jerking when braking lightly.
Air-Ride suspension is really, really nice. Loaded or unloaded, the Haulmark 5x10 enclosed trailer sits level using my 4" riser as shown.
Worth it? Yeah, I almost bought a Ford Flex Limited just because of the factory trailer kit. Seeing the three-pointed star instead as the garage door rolls up is much better. Totally worth it.
Raul of the U-Haul was tapped for 3 hours of his time to make the final connections. I did all the hardware installation. Tapping into the skinny Can-Bus wiring with ScotchClips proved risky. The U-Haul people had bulb-socket connectors that ensure a more positive contact and don't confuse the computer.
The Tekonsha IQ inertia-sensing proportional brake controller is a nice device. Very linear in operation, without jerking when braking lightly.
Air-Ride suspension is really, really nice. Loaded or unloaded, the Haulmark 5x10 enclosed trailer sits level using my 4" riser as shown.
Worth it? Yeah, I almost bought a Ford Flex Limited just because of the factory trailer kit. Seeing the three-pointed star instead as the garage door rolls up is much better. Totally worth it.
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Interesting story, like a soap opera. Well written and documented. Welcome to the forum!
Our '07 came with a hitch, but no wiring. I think it was used for a bike or cargo carrier. Wife would like it removed, but I put a rubber plug in it, and there it stays. Enjoy your R!
Oh, and it took me a while to figure out just where in Texas you are! Ha!
Our '07 came with a hitch, but no wiring. I think it was used for a bike or cargo carrier. Wife would like it removed, but I put a rubber plug in it, and there it stays. Enjoy your R!
Oh, and it took me a while to figure out just where in Texas you are! Ha!
