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Discussion Starter · #1 ·
Okay, so I've figured out how to get a hitch on the car. Now I need wiring. The only problem is that Mercedes offers absolutely zero US wiring adapters. This is straight from the dealer service center several local installers.

According to a one installer, everything must be wired separately using splicing, sensors and relays that detect when brakes and signals are turned on. If you try to tap into the light circuits directly, you will throw computer error codes. If you have LED tail lights then it's even more complicated. You can't get much more "German Engineering" than this, is all I can say.

So, has anyone attempted this?
 

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I've seen amplifier kits on Amazon. Haven't done it myself. Any new car verifies lights as a matter of safety. This is done by measuring resistance or current. You must be careful how you modify this.
 

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Discussion Starter · #3 ·
I've seen amplifier kits on Amazon. Haven't done it myself. Any new car verifies lights as a matter of safety. This is done by measuring resistance or current. You must be careful how you modify this.
Yes, a lot of new cars verify lights, but they also let you add a hitch at the factory an/or they make adapter kits for towing. Every Toyota uses the same T-connector. Mercedes does not, if it doesn't come from the factory with towing, which I was told I could not order, then they offer zero support on adding it after the fact.

This is probably my first and last Mercedes. I'm never, ever again driving a new car off the lot that doesn't already have a hitch on it.
 

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Ned, I hear you, it really sucks not to have a hitch! I have decided to go the roof rack route.

When I was buying my GLA I talked to the parts manager about hitches and he said one reason they didn't put the hitch on as an option is because of all the changes they would have to do to the electronics. They just didn't want people to put on an after market hitch and mess with that stuff. So, even if you end up with a hitch, I would be careful much wait you put on it. I would think bikes, skis, etc. is fine but pulling a trailer may be a problem for the car/SUV.
 

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The hitch is an option in other countries. In England word is that the GLA has become popular for towing caravans (camper trailers) up to 3500 pounds. I'm not saying I'd want to do that, but apparently the vehicle can tow. I have not gotten a good reason why we can't order the package in the USA. It is frustrating.
 

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Discussion Starter · #6 · (Edited)
I got a U-haul to do the hitch, but they were unable to get the lower bumper/diffuser completely flush with the rest of the bumper afterwards. They told me that was the best they could do, that they would remove the hitch at no charge or I could try a body shop. I'll try to get a picture uploaded someplace.
 

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Discussion Starter · #7 · (Edited)
The hitch is an option in other countries. In England word is that the GLA has become popular for towing caravans (camper trailers) up to 3500 pounds. I'm not saying I'd want to do that, but apparently the vehicle can tow. I have not gotten a good reason why we can't order the package in the USA. It is frustrating.
Yes, it's EXTREMELY frustrating, especially given that this vehicle appeals to active, urban professionals who like to haul kayaks and bicycles and the like on the weekends. There are several in my urban neighborhood with its narrow streets and tiny early 19th century garages. The reason I bought one in the first place is because I saw a couple parked on the street. I was not even aware that Mercedes made a compact crossover that size for the US market.
 

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Absolute Bollocks

I've been through all of this right now, the last step is doing the integrated wiring solution.\

Luckily I am an electronics engineer by trade so it will be easy.

First off lets address everything here out in the open.

Towing. It is entirely marketing.
They realize that while the rest of the world is smart, us in North America have a very American attitude towards towing and think we need a GIANT vehicle to tow anything.
So MBUSA/CANADA decided to nix the towing option for the GLA here to upsell us the GLE (I did really want one) GLK or GL class

Regardless of this horses end decision we can still tow plenty with this wonderful car when properly equipped.

First off the HITCH. Any REAL qualified shop can install a hitch in a couple of hours.
There are a few options, including importing a hitch from europe.
Lets address all of these.

1. importing the hitch has legal issues since no welded loops for chains are available.
2. the imported hitch from westifalia has you not installing the bumper reinforcement as part of the standard installation.
WTF! westifalia!
3. the ball mount would be non standard and require changing..... iffy.

Local hitches. Curt, Hidden Hitch, etc.
1. both of these are great options. provided you do not mind having a receiver sticking out uglifying your GLA
2. Hidden hitch's chain loops stick down lower than Curt's so you lose ground clearance on the back..... sucks for turning parking blocks into your hitch.
3. both are rated 3500lbs +

One last dead option.
Execuhitch/invisihitch,
I contacted this company after viewing their website and had high hopes of getting a drop in 100% awesome solution.
They dropped the ball on this big time for me. Very Annoyed and I would recommend everyone phone them and complain.
after a year of emails back and forth it seems the company either doesnt care or is now exclusive to bmw.

Installation of local made hitches.
I did it myself.
The hardest part is finding all the clips, and screws, and popping said clips without having a heart attack because you broke one.
Really I will post the CURT hitch PDF up here if somoene wants it, but there needs small changes. that I am addressing with CURT soon enough.

My own installation I did entirely myself AFTER modifying said hitch so it is not an ugly mess.
Why CURT or Hidden Hitch dont offer this? I dunno.

Advice, if you are not mechanically inclined, please find a local dealer willing to work with you or a high end body shop to install the hitch. It is very much worth the price and peice of mind that they will know what the **** they are doing to remove the rear bumper facia without problems AND be able to put them back as the factory intended.

I really cannot recommend enough the CURT hitch. You can get it at a great price, it has EXCELLENT build quality and you can if you are handy or willing to spend more with a hitch building company get it modified to be 100% invisible.

Wiring.
FFS people, yes the computer will interrogate the rear lamps. whoptee doo.
properly installed a POWERED standard trailer lamp interface will work perfectly fine.
Cheap units will throw codes but properly designed units will be invisible to the computer since no loads are placed in addition to the standard loads the normal tail lamps in the car provide.

second post and update to come soon.
I plan on using my hitch for my bike rack, jetski, and small boat.
I am also installing a tekonsha wireless brake controller unit so I can have brakes on my boat trailer and have the option of towing greater loads.
European specs put this car as capable of towing 1800kg with braked trailers, and tow car awards website rated this car very highly for towing. it was these accolades that made me choose the GLA instead of keeping my Ford Edge another year while waiting for the GLE. PS, Avoid Ford Edges for any serious driving or towing, the transmissions (6F50, and AWD PTU) are not designed for a lifespan of greater than 4 years in standard driving due to poor heat management and non stress relieved welds on the planetary drives.

I currently own a 2015 GLA 250 4matic, and Audi 90 quattro sport.
have 20 years experience as an Audi/dodge/ford at home mechanic as well as heavy modifications on racing audi's as well as my EE skillset.
photos to come soon! :D
 

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Here's the photos of the hitch partially through modification, installed right before the rear facia goes back on and after installation.

Gla Hitch by Natan Cratzo | Photobucket

Functionally it is fricken amazing.

as you can see I modified the original Curt hitch
https://www.curtmfg.com/HitchLookup/find?year=2015&make=Mercedes&model=GLA250&style=All
to have a vertical receiver tube with a 5/8 pin to automatically lever lock in place.
During initial design conception I originally wanted to use a linear actuator to make sure the unit was locked in place and add cool factor.
That said the simplicity and compactness of the manual spring lever system could not be beaten, especially considering I knew there was alot of room up there but yet I was not sure how much of that room was available to me.

Operation is as simple as the video shows.
Slide the lever to the right, which retracts the lock pin. insert the vertical receiver. release the lever and the pin auto locks into place.
For added security you can install an interlock pin on the 5/8 pin to absolutely prevent extraction.

If I ever rework this mechanism, it will have a solenoid interlock system to automatically engage and prevent pin extraction.
However, that said, the class 3 lever mechanism has a 20lb spring on it, which is in constant load on the pin, preventing extraction.
Yes, not perfect, but more than good enough considering many other life saving parts are also held together with springs, etc.

Anyway, moving on.

installation notes.
The curt instructions are simplified and mostly correct.
Notes needed. to finally remove the bumper facia, open the rear hatch, remove the 3 bolts holding the plastic tray cover on the hatch latch frame. 2 bolts are covered and hold on the cargo strap loops.
With that out of the way, you need an ultra deep 10mm socket to remove the 2 nuts holding the rear facia onto the back of the car. I used a deep socket 10mm 1/4" drive shoved into a peice of 12"x1/2" id pipe. you can use a setscrew or a throw away socket welded to the pipe for this purpose. The reason for the ultra deep socket is the alignment pins/studs for the rear facia are about 5" long, and the nut is inside the framework of the car so wrenches will not work. shove the deep socket over the pin using the pin as a guide, get it over the nut, pliers to start it rotating unscrewing, and then unscrew by hand. done. do not drop the nuts in the frame, but magnets or claw pickup tools work well.
With the facia free the last step missed by the Curt instructions is the unplugging of the rear radar modules for BLIS system. pretty obvious.
cut the zip ties and unclip the sensor plug. for some reason the seals failed in my sensor plug so I cleaned it up and filled it with silicone grease to prevent future corrosion. (meh, im not going to be a warranty ***** about this, as they would have to remove my bumper AGAIN and probably yell at me for the hitch.)

As you can see there are gobbs and gobbs of room in there, so I can plan on having a magnetically held wiring loom in there and hide it very slickly. Since I'm planning on using both 7 way and 4 way flat connectors I will be able to hide them in different locations as needed.
The 7 way for braked trailers, and 4 way flat for wimpy trailers.

Fears?
4 weeks earlier, at the local Lowes, I came across a cool guy hauling 2000+LBS of concrete bags and construction supplies in a braked trailer connected to a 3 year old ford focus. The saving grace was it was a manual focus. Yet, after talking to him and seeing plenty of evidence from the euro market on towing with smaller cars, especially the GLA, Im very confident.

Today, towing around the jetski (lamps not wired up, yea I know) the car drove phenominal.
Towing with a turbo engine is worlds different than normally aspirated. Even my dads 1500 hemi dodge pickup the jetski is noticable.
The GLA? no, aside from minor noises from the hitch chains, and minor clunk (way less than the edge), I have to say its a great tow car.
Power is not a problem, and it tows beautifully. Yes its slightly slower with the 600+ lbs of trailer/jetski but it is not in any way causing a loss of confidence in driving this thing.

Personally, I would suggest towing in sport mode, so the engine and tranny are kept im more appropriate gears for higher loading.
Visability with the jetski trailer is difficult because its such a small trailer, but accel, take off, backing, parking, launching the jetski on the ramp, retreiving the trailer off the ramp loaded and unloaded are absolutely no concerns. If it was my boat I might consider using off road mode so the engine/throttle response, and gearing again are more appropriate for low speed maneuvering of a highly loaded trailer.

All in all a win.

so.
reiteration.
CURT hitch (which comes with the wiring module for computerized universal usage)
get it installed by a PRO who is german vehicle competent.
Take my notes on the small missing items from the curt install guide manual.
IF you are satified with a receiver hanging out of the car, then so be it.
IF you want hidden mechanism like mine. find a shop willing to do the modifications. Parts cost me about 100-150 of a receiver tube, 5/8 pin, flat steel, welding rods, paint, grease, and 5/8 bushings and retraction spring. Farm store like princess auto or harbour freight will have what you need.

Competent hitch shop should be able to do this, as litterally all my work was cutting and grinding and welding, nothing fancy.

I will update you guys once I get the trailer wiring going on the car.
I am fairly confident it will be an easy peasy job, since the tail lamp modules have basic wiring at them, they are easy to get to and remove, and use incandecent bulbs for many functions.
 

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Watching them install a Curt hitch on my 2015 GLA45AMG. I am only using for a Thule Helium bike rack so no wiring but I asked them, said they use a Curt powered lighting adapter all the time, they work perfectly and does not bother anything in the car. Going good so far, even with me watching. Will post some pics tomorrow.
 

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Wow... so towing (with wiring) looks like a serious PITA. My skills aren't up to par and not sure my stomach is either... the hitch is one thing and if was just that I'd probably go for it, but I have to tow a 2500' jet boat so wiring is a must. That is what really scares me.
 
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