I am extremely pleased and impressed with the Curt Hitch and Pulse Width Modulation Converter that I've installed. See photos. I removed the aluminum heat shield on the driver side to find the "access hole" in the bumper beam, but I gave up trying to thread the metal fishwire through the mounting hole per the instructions.

Instead, I was easily able to thread the wire through the back end opening of the bumper tube in a manner similar to the suggested technique for the passenger side via the removable square access cover. There is enough clearance between the plastic bumper cover and the bumper tube to allow this access. This proved much easier than the suggested technique using the access hole in the bumper beam.

The Converter mounted easily in the cavity behind the access panel for the driver side tail lights.

Also, I installed an aftermarket ultrasonic backup alarm and placed the control unit for it in the spare wheel well as seen in the photo. See my separate post which shows photos of the sensors in the bumpers.

 

Not sure how I missed all your mod posts but congrats on awesome looking work!

A couple of questions:

1) Anything odd or unusual about the Curt Hitch installation in regards to the GLK (bumper removal? Drilling? Other?)

2) Is the Pulse Width Modulation Converter for towing a trailer?

 

1) Not really anything unusual. You do not have to remove the bumper, but you do have to lower the exhaust. Rather than struggle with this, I took the GLK to my local independent shop and they disconnected the exhaust from the rubber hangers and then wired it up temporarily with some coat hangers so I could drive home. It was easy for them 'cause they had the right tools. Cost was $40 labor and well worth it. I did raise the rear end on some home-made blocks of 2X10s. The rest of the installation was straight forward and I did insert the bolt and plate into the frame rails through the rear of the rail as I described. Make sure that you have the correct bolts when you do this step -- there are some slightly longer bolts that you might grab in error.

2) Yes. My '10 GLK and perhaps later model years has one bulb connected to a wire that carries what measures about 4 volts DC (it is actually an PWM signal) for tail light and also carries 12 volts DC to the same bulb for brake light. There is also a separate tail light that has a 12v line, but you have to use the Converter to separate out the brake light. (There is probably an option to send the PWM line to a trailer light which, just as on the GLK, could serve both functions, but the trailer brake light would be on all the time that the GLK's tail lights are on.)

The Converter takes the PWM signal and creates 2 separate lines -- both 12 volts, one for a trailer brake light and one for a trailer tail light. The turn signals are on separate lines.

On my '10, here are the color of wires on the driver side tail light assembly:
Brown: Ground
Blue/Grey: Reverse (used on my ultrasonicn backup alarm posted separately)
Black/Red: tail light only bulb
Green: ?? Not sure -- fluctuates with turn signal, but use the Black/White below
Black/White: Left Turn
Pink: PWM tail and brake bulb

On the passenger side the turn signal is Black/Green.

Hope this helps.

 

Thanks Gordon! I have the factory hitch and had to buy my own hitch ball assembly. It has close to 3" rise which I think is going to be too much for my standard 1,500 lb. boat trailer on 15" wheels. What type of trailer are you towing and which Curt hitch ball & what rise are you using?

Wayne

 

I just plan to use a U-Haul. I did go to the local U-Haul and have them check the hitch and 4-wire connector for proper functioning and all was OK.

I got a 2" chrome ball and 2" chrome hitch from Curt. Sorry I don't have the part number, but as I recall it was the only chrome 2" hitch available. It puts the top of the ball about the same height as the top of the receiver. Or the hitch can be flipped 180 degrees and the ball re-attached, placing the top of the ball about 4 " above the top of the receiver. Perhaps the hitch you have can be similarly flipped to lower the ball.

 

The ball contraption I found quite by accident in a small town country hardware store is one piece with two bends in it and 2 5/8" rise. One of these days I'll find my Round Tuit and hook up the boat trailer. I'll know then if I need another, lower ball. I see that CURT offers a similar drawbar with 3/4" rise. That may be the answer. Thanks for all of your help.

Wayne

 

You bet! Hope you find a good solution.

 

nicely done...i need a hitch too.

 

Yes Curt makes nice hitches, I had one on my jeep,,, now I want to get one for the GLK.. Tks for the tip

 

A bit of warning on the Curt Hitch. There was some interference on the driver side with rear muffler on mine. The muffler is connected to the forward pipe with a "ball" type joint so there is no adjustment. There was clearance when the car was cold, but the exhaust pipe grows about 1/2 inch when hot, so I would get a lot of noise when it contacted the hitch. I talked to Curt about it and showed them my plan. They said the part I ground off was not structural. It is easier to take this material off before mounting. I used an electric grinder with a metal bit and did it in-place, being careful not to hit the muffler. When you trial fit the hitch, make sure there is plenty of clearance between the hitch and the mufflers.
Also spray the rubber muffler hangers with dish washing soap to make them come off easily.
I do like the hitch. It is strong and looks good.

 

That install sounds like it would be a headache. So did you actually take down the exhaust, to install the hitch? When it's all installed you say the exhaust expands about 1/2" , wouldn't the rubbing on the side plate of the hitch eventually cause a hole in the muffler?

 

I can't seem to get my PDF to show up even though it says I have attached the PDF to the previous post. So I will try again, this time as a jpg
Basically it shows cutting off 1/2 inch of material from the hitch that is rounded in front and between the lower bar and top plate so it is straight and vertical.

 

Taking down the mufflers is the hardest part. Once you figure it out it really is not that bad. You do not need to disconnect them. Use SLK55er's methods for fishing the nut. Probably takes a total 1-1/2 hours.
According to Curt, they had not heard of another case such as mine, but I thought I would warn people there is that possibility. My GLK is an early 2010.
I use a Thule 990 Doubletrack bike carrier in it. The carrier keeps the bikes on their wheels and is very easy to load. On my RangeRover Sport, which has a plug-in type hitch, the carrier does a lot of front to back dipping going over railroad tracks and such. In the Curt, most of that is eliminated.

 

Thanks for all the info

 

Thanks so much for posting your wiring SLK55ER. I tried to do my own circuit testing but my decades old tester and multimeter must have been too much draw to work with PWM. Couldn't tell which one was the turn signal.
Your connections were identical to my 2012's so hooked up a Curt 59236 and all is well. I did mount it on the drivers side as the longest wire was for the right turn signal, but still had to lengthen it a foot or two to run it along side the existing harness that goes across the back. Power was taken from the trunks 15A power supply on the drivers side. If it can handle the electric tire pump it will be fine running trailer LED's.