CJBROWN

Yeah, if you mount the module down low like my pic then the green wire will reach all the way across and attach near the terminal for the right hand lamp. And you have to add a length of feed wire to reach the cigar lighter outlet. How handy is that to have switched power back there?

My trailer tows way better with a couple of bikes on it. Nice and smooth.
Empty it bounces a lot and you can feel it pulling the car. Seems like it should be the other way around.

These cars don't weigh that much, I'm not sure I'd want to spend much time towing its max. People do the darndest things though, 'specially in Europe.

Anyway, piece of cake. What a way to replace a pickup truck, eh?

On a side note...some jerk on the freeway in a toyota flatbed dumping dirt and rocks all over the freeway...I now need a windshield. Cracked all the way across. Got his plate and called the CHP to report it and insurance still wants me to pay. Worthless sons-a- &%*&^*s.

NevadaNick

I have a GL350 on order and ordered with hitch. Told my wife it was so i could take her car to the races.

Spooner

Man that sucks about the windshield. They are so vertical they are really susceptible to damage-mine has a few pock marks on it too.

My trailer is fairly heavy duty and a little bigger than yours but I doubt I will tow it empty that much. I remember it would bounce around a little behind my duramax empty though. I think it will be about 1,000 lbs loaded. Did you just put it in D and go, or did you manually shift it back to 6th on the freeway? It will be weird not monitoring boost, EGT's, and trans temp while towing haha!

fragil

Hi Spooner,
I did already several 1.000 kms with my GLK 220CDI with a caravan of about 1.300 kg behind; no problem at all. You can just put it in D and go. The only time that I shift "manual" is descending a hill; you have to put it in a lower gear to use the engine brake more efficient, otherwise the speed will be to high.

CJBROWN

I use the 'S' shift mode almost exclusively. Starting off in 2nd is just dumb. The only time I leave it in 'E' is in the rain. And it doesn't rain very often in So-Cal.

But yeah, tow-haul mode is da bomb on those trucks. I only chipped mine to stage II with a hypertech so didn't have to worry about trans or exhaust temps. Sure was slick though, especially shifting down for you.

Yes, manual shifting for down grades for sure. If I was towing heavy, say over a couple of thousand, especially with grades or summer temps, would figure out a way to add a trans cooler. Pretty cheap and help keep them from overheating the fluid. Should shorten fluid change interval too if there are many tow miles. I'm sure that 7-speed is an expensive slushbox.

fragil

Chris,
You are completely right about the temperature.
That is why in Europe you order the tow hitch directly from the factory they mount automatically an extra cooling system.
For that reason we pay about 1.000 € (1.400 $) for that option.

CJBROWN

I'm fairly certain that entails a larger or higher capacity electric fan and a trans cooler. I could be mistaken, but think that's it. If there's a larger rad core then that would be an obvious advantage. Perhaps someone could confirm that.

Bottom line is that for a 1000-1500lb trailer or a bike rack, the CURT hitch is a great solution.

Spooner

Exactly, towing more than about 2k lbs would probably suck with these things, but around 1k should be fine. Thats basically like having 4 larger adults in the vehicle if you really think about it.

Race got canceled for tomorrow due to weather but I might head head down south to ride tomorrow anyways. Need to make sure I have a drop hitch that will work for my trailer.

fragil

CJBROWN,
Indeed the difference is indeed a bigger electric fan an a trans cooler.
With the caravan I always drive in "D" without any problem.

CJBROWN

There's another thread that got started recently about hitches and towing, so I thought I would update this one with performance results after some miles.

Took a 400 mile trip up to the Lake Isabella area from the LA basin a few weeks ago. Trailer and bike in tow. The route goes up and over the 'Grapevine' pass which is like a 8% grade for 10 miles are some darn thing. It's a hellatious run for anything towing. Lots of overheaters and stalls on the side of the road, semi's blown up, you name it.

The little GLK did just fantastic. Set the cruise at 60 and just shift it down to keep the revs at about 3-grand. It just walks up and down the grades without batting an eye. Very comfortable to drive. In fact, it is the most comfortable over-the-road vehicle I have ever made a trip in. The auto climate control, cruise, and comfy seats just make it a breeze. The big sunroof is a really nice feature as well.

BTW, found out a nice little feature on the cruise control. Once set, if you bump the lever up or down lightly it adds one mph up or down. There is a second detent though, and if you hit that it sets the speed to the next 5mph increment. So if you're at 62 it will bump to 65, then 70. Really a nice feature.

I also realized recently that if you don't have to hold the turn signal for lane changes. Just bump it right or left and it will flash 3 times and cancel itself.

These little niceties including the all windows auto up and down are really nice techno features of the car. Very nice little luxury extras.
Now if I just had heated seats!

emdem

True. Once The hitch is installed, the dealership has to change the setting to allow for the trailer hitch. I have an OEM trailer hitch sold to me after I purchased the car (=not cheap).

CJBROWN

Evidence please.

I think you guys are making this stuff up.

emdem

Call and talk to your service tech before you make allegations. You can go and search the WIS for all the evidence you need. It took me months to collect the data prior to the 2011 WIS release from the dealership because they had never done an OEM after delivery. Yes, the hitch ties into the network of the car and there's a module that comes with the hitch that ties into the rear access module.

Good luck to you! Just for fun - here's the control unit part # A204 545 8132

CJBROWN

And what exactly does the 'WIS' (whatever that is) actually say??
I was looking for hard evidence, not "I researched for a month" - what exactly did you find?
What is this, a guessing game? Come on!

emdem

Wow. You're kind of an a**hole aren't you? Generally, when you ask for help, that's not how it's accomplished. Take care and best wishes to you. M.

CJBROWN

Personal attacks are prohibited on the forum. Any forum for that matter. What you think of my personality or approach to getting infomation is irrelevant to the topic of discussion.

You play a guessing game and then make a personal attack when you're called on it. Childish behavior, name calling. You must have been one of those school yard bullies.

And BTW, read thru again, you'll see I did not ask for help - you piped in with your inuendo and I asked for evidence/facts to back up your claim. If you have something valuable to add why don't you just do that instead of making vague references?

Nola

OK folks, cool it. No need for name calling or being offended by scepticism. It's the internet after all.

Besides, CJBrown did a great job in documenting what he did.

CJBROWN

So, just to try to verify some of the claims about traction control I did some searching and found the following:

ESP = Electronic Stability Program , Mercedes Benz trademark name for electronic traction control. This feature is included on the GLK350 model.

TAS = MB's TRAILER ASSIST SYSTEM, which is an extra device that uses the ESP sensors in the vehicle for additional traction and sway control when trailer towing. This is offered in ML, GL, and Sprinter models. Not in the GLK from what I could find.

Here is more discussion on the topic. You'll find some helpful info as well as more confusion and questions:

http://sprinter-source.com/forum/showthread.php?p=140258#post140258
http://sprinter-source.com/forum/showthread.php?t=6918

A quote from conceptcarz.com:
In addition to a tire pressure warning system, the tried-and-tested Electronic Stability Program (ESP®) for the GLK incorporates a vehicle/trailer stabilization function, which helps maintain control while towing a trailer by applying the individual wheel brakes as required. The GLK offers a maximum tow rating of 3,500 lbs.

http://blog.yourmercedes.com/certified-mercedes/mercedes-towing-capacity/
Discussion here on MB towing and the ML and GL series, and mention of TAS – TRAILER ASSIST SYSTEM – available on these models and Sprinter vans. TAS is not offered in all models, highly doubtful for the GLK (it’s too small). TAS is integrated with the ESP (Mercedes electronic stability program) sensors in the vehicle to help with sway control and fishtailing when towing a trailer.

From CAR NEWS site:
In addition to a tire pressure warning system, the tried-and-tested Electronic Stability Program (ESP®) for the GLK incorporates a vehicle/trailer stabilization function, which helps maintain control while towing a trailer by applying the individual wheel brakes as required. The GLK offers a maximum tow rating of 3,500 lbs


And this from emercedes.com:
As well as a tyre pressure loss warning system, the Electronic Stability Program (ESP®) incorporates a vehicle/trailer stabilisation function as standard, which can defuse precarious handling situations resulting from towing a trailer at an early stage by applying the individual wheel brakes as and when required. The permitted towing capacity is 2,000 kilograms.
Unfortunately there is no mention of something that is changed or adjusted for ESP when a hitch is present.

It is entirely possible that there is a module of some sort that is part of the factory trailer towing wiring harness that notifies the onboard ESP that there is a trailer attached and additional weight is to be considered in how ESP responds. However from what I can find online is that this is an option for the TAS that is not offered for GLK. From what I can tell the ESP in the GLK is optimized for vehicle whether towing or not. Something from a technical manual stating otherwise would be of benefit to us all.

It has also been noted that without said connection the vehicle would drive as without ESP when trailering , like we’ve been doing for a gazilion years.

Anyway, if more technical information can be provided on what adjustments are done to ESP for trailering and what to expect, then we would all be more well informed.


EDIT: BTW, 'WIS' is MBZ's WORKSHOP INFORMATION SYSTEM, similar to their EPC parts catalog, but with repair, electronics, wiring, and diagnosing information and data. It is a subscription based program you buy and install on a computer. Said to be confusing and difficult to setup for use. I do have a subscription to EPC that is about to expire. Was valuable for getting part numbers and such for my old benzo.

emdem

See? No b.s. ... you'll need this... (see attached).

emdem

And this... (see attached).

CJBROWN

That helps a lot, thank you.

There is definitely a SAM (Signal Acquisition/Activation Module) control module for sensing the presence of a trailer connection. The ECM or ESP is also programed to accept signals from the SAM. My assumption is to assist with modifying the reaction of the ESP or electronic traction control.

Frankly, for me, for a 1200lb trailer, I'm not going to sweat it.

The next primary difference in the 'factory' retrofit for a hitch is the blower fan. The bulletin posted says warranty and 'good faith' (whatever) is invalid unless a 'higher output blower' is installed. Hmmm...so I pulled up my EPC parts program to see what they have thinking maybe I would invest in this upgrade for safe measure. Well, lookie here, the very same part number for stock or for "550" which is the trailer hitch presence coding:



So, since about 2004 the blower motor part number has been the upgraded or higher output cooling fan installed on all of the GLK's world wide. I'm not going to sweat that either. Should I have a major warranty claim that is disputed due to my trailer hitch install I can easily refer to this parts list for the blower fan status.

I was also surprised to see there was no option for an increased capacity transmission fluid cooler, in fact it does not even show up in my version of EPC which is for NA cars only (annual subscription is free for NA cars). So I'm not sure it even has one. I'm curious now, will have to go out and see if there is actually one on there. In any case, if I was pulling more than a couple of thousand pounds I definitely would add an auxilliary or aftermarket cooler.

As I've mentioned before, I wouldn't want to use this little car for towing more than a couple of thousand pounds anyway. While it's rated up to 3500lbs properly equipped, I just would rather have a heavier duty tow vehicle for that kind of application. Like a US-made pickup truck.

Anyway, there you go folks. Everything you ever wanted to know about trailer hitches for the GLK350! Thanks for looking up the service bullitins emdem.

larimer

I just installed the Curt trailer light module, following the CJBROWN wiring photos/instructions, and everything worked except the stop lights? The parking/running lights worked, turn and 4way flashers worked but no brake lights. On the module park and stop are the same wire, red w/brown stripe, tied to the pink on the left rear light connector. Anyone have any idea what might be wrong?

CJBROWN

The stoplight and parklight/taillight is on the same circuit. Mine is connected to the top wire (pink) on the left hand lamp assembly.

The left turn signal is connected to the next wire down, black w//white stripe.

Based on your post that's how you have yours connected. Does your module part number match? It could be a defective module, last resort.

Is it connected to 12V power? It must be or the other lights wouldn't work.

Are the brake lights for the car lighting up? You're just not getting power to the trailer brakelight wire? Are you using a test light or multi-meter? Maybe the brake lights aren't setup right on your trailer wiring.

larimer

I've tried other trailers, a flat four tester and a multimeter and still no brake lights. I've emailed both Curt and etrailers where I purchased the unit. I'm down to a defective module. Because both the parking/running lights and the stop lights are on the same wire, the module must detect a change in voltage to the vehicle stop light. This stop light is a single filament bulb that gets brighter as the current is increased. The module isn't sensing this change and therefore isn't switching the power to both turn signal circuits. IMO. I'll hopefully hear from the seller and manufacturer soon.

CJBROWN

Sure sounds like the wrong unit or a defective one.