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I have a question about unhooking a travel trailer. I have searched the forum and I see some of you tow some large Airstreams. I found only one mention of the problem I am dealing with and it really did not get any responses. With the airmatic pumped up for self levelling how do you uncouple the trailer without the airmatic following the trailer up as you unload the weight of the trailer tongue off of the ball? I am also looking to buy a newer trailer and found something I like but the tongue weight is listed as 890lbs. With creative loading do you think I could get the tongue weight down to something reasonable. The propane tanks are at the back and I thought moving the batteries to the back also would help. The trailer has a 44gal. fresh water tank so keeping that partially full may also help if it is located behind the axles. Any opinions are welcome.
Thanks,
Bob
Other than saying "good luck cutting the trailer's tongue weight in HALF" I don't have much to add except don't sweat the unhooking. The car will come back to its happy place quickly after a few feet of driving.
Also, if the fresh water tank is located rear of the axles you'll actually INCREASE tongue weight by leaving it less than full.
edit again: a block under the trailer jack is handy if more elevation is needed.
Last edited by rapidoxidation; Jan 29, 2023 at 10:52 AM.
I have a question about unhooking a travel trailer. I have searched the forum and I see some of you tow some large Airstreams. I found only one mention of the problem I am dealing with and it really did not get any responses. With the airmatic pumped up for self levelling how do you uncouple the trailer without the airmatic following the trailer up as you unload the weight of the trailer tongue off of the ball?
Could you manually select the highest ride height using the button on the center console, uncouple the hitch, select the normal ride height again, and then drive off once the truck returns to normal?
Okay I think I will just have to play with the self leveling system to figure it out not a big deal and as to the trailer I searched the specs on the trailer and they are a bit weird to me as far as the weights go. The uvw is listed as 4910lbs. the gvwr is listed as 7890lbs. so the payload capacity is 2980lbs. who puts almost 3000lbs of stuff in their trailer? I am going to get in touch with the dealer and see if they will take a tongue weight reading for me as it sits now. Something is not right here because the tw is not 10 to 12% of gvwr or 10-12% of uvw.
bob
Depends on the trailer... A "toybox" trailer with living space and a garage can easily tip 3K pounds of stuff with a 4 wheeler and couple of dirt bikes.
Yup hadn't thought of that but this is a 26ft regular travel trailer with one slide on the street side. there is only one outside storage area at the back on the curb side, propane tanks are in the back on the street side along with the hot water tank. I am guessing that the fresh water is also at the rear somewhere between the propane tank storage and the one storage spot with access from outside. It has a center bathroom so I am guessing the the black and gray tanks are probably over the axles. kitchen is up front which will add some weight to the front just not sure how much. the only thing up front on the outside are the batteries which from what I've read are hard to access, that's why I would consider moving them to the back into the one semi large storage area. With all that said a trailer with an uvw of 4910lbs and that should be with water and propane full should have a tongue weight around 500-550lbs. Having a front kitchen shouldn't add another 340lbs should it?
Bob
Just a thought, the GVWR is related to the axle ratings (among other things). So if they put beefy axles on the trailer, the manufacturer may be able to list the GVWR as a high number, even if it's not practical to put that much weight inside. Although It's pretty easy to pack a couple thousand pounds of fresh water, waste water, food, gear, firewood, bikes on a bike rack, etc etc.
I've never had a problem with my load-leveling while unhooking the trailer. I tow a heavy trailer (7000+ pounds loaded) and the tongue weight is close to the max but still under. I use a weight distribution hitch. Originally my spare tire was under the tongue but I moved that to the rear bumper to reduce tongue weight. And when I load heavy coolers and cases of drinks, I put them over the axle and not too far forward. I put tires on my GL that can handle higher pressures, and I air up the rears to the high 40's when towing my heavy trailer. I've towed the trailer over the Rocky Mountains and along the 70mph+ Montana freeways and it did fine.
One last thing is that I wouldn't trust a trailer manufacturer to be accurate on their ratings. The tongue weight depends on the trailer configuration (optional AC units, etc.) and how you've loaded it. They probably have one rating for that length of trailer, they may not have a specific rating for each interior layout. With a heavy trailer, you need to take it across trucking scales as soon as you can, you may be surprised what it actually weighs loaded.
I am thinking of ways to justify buying the trailer but in the long run the tongue weight is just too much, from what I can deduce from the photos all that can be in the rear of the trailer is already there other than the batteries and they don't weigh enough to make a difference because I would have to get the tongue weight down to around 650lbs and I don't think that is doable so I have to move on, too bad really like the layout.
bob
Tomorrow I'm going to pick up a new trailer I bought. Never thought I would go backwards in length, that is why I was looking at the 26 footer,in my mind I needed bigger. The new one is a grand design 17mke, about 21 ft total length GVWR of 6300lbs with one slide. The wife and I saw it at an RV show, liked it, bought it. I did a little more research in the x164 and w164 threads and came across some more info concerning the airmatic and trailer hook up, apparently you should shut the vehicle off and leave one or both doors open to hook up. That seems to be the starting point so I'll fly at it soon.
So I was unhooking my new trailer, shut the gl off left the door open and disconnected everything and started to lift the trailer with the power tongue jack and the gl is coming along for the ride. So I stop and figure this isn't good so what to do? Well it was hot so went to get my drink from the console and I closed the door and just like that the airmatic releases pressure and the gl drops out of the trailer coupler, problem solved. So I think I've got this airmatic trailering system figured out. Hooray!
So, after a summer of trailering all my concerns were for naught. What an easy system to work with, the self levelling and the way the ball just drops out of the coupler. I think Mercedes got their system right. Mind you I was under the max trailer weight by several hundred lbs at least. So some photos if anyone is interested.
Bob
So, after a summer of trailering all my concerns were for naught. What an easy system to work with, the self levelling and the way the ball just drops out of the coupler. I think Mercedes got their system right. Mind you I was under the max trailer weight by several hundred lbs at least. So some photos if anyone is interested.
Bob
does your vehicle have the factory installed brake controller adapter (green female connector) under
the carpet in line with the brake pedal?
does it work properly when using brake controller?
I plugged a Tecumsa brake controller into mine and no brake signal coming into the connector for some reason. Dealer no help at all, provided a “typical” wiring diagram, not specific to my 2014 GL550, below.
I have an ML not a GL but I do have the trailer package with the green connector under the carpet as you mentioned. Plugged in a Prodigy brake controller and it worked as expected with zero issues. If you have the green connector, the proper adapter, and a trailer brake controller, you should have everything at the trailer electrical connection WHEN A TRAILER IS CONNECTED. The car is smart; it won't energize the rear socket by the ball hitch until it knows there's something there. IIRC, YMMV and all that.
Yes my controller works fine when towing. Do you have the factory trailer package on your vehicle, code 550? Why do you think there is no signal, check your fuses, I seem to remember mention of blown fuses causing problems, I think that fuse block is under the second row seats. Also is your controller set up properly? Lastly you may need your rear sam unit reset by the dealer.
Bob
This is the controller I bought along with their universal pigtail and hooked everything up according to the pictured wiring codes. the little knob is my brake control.
Bob This kit can be bought from MB.
Bob, possible to get better resolution to read what is in bottom right corner within “wire desc”?
same for this doc - would like to read what it says in 1st paragraph. Thank you!
Controller works fine on my Rv pulling trailer so that part is ok. Leaves the interface 4-wire harness between MB green connector & brake controller + fuses + possible rear SAM reset (not sure why a reset would be in order but this is MB so logic not always whatcha think).
Lastly, will find my build sheet for car & report back on option 550 factory trailer wiring pre install. Cheers
L&N, just put your vin in here: www.lastvin.com
and your build will be shown.
I ordered my Mercedes specific adapter straight from Prodigy; there was nothing to do but plug one end into the supplied green connector under the carpet and plug the other into the controller. Easy peasy.
Last edited by rapidoxidation; Dec 9, 2023 at 11:08 PM.
Sure, no problem. There are some posts on this site that address your problem. I just read one from 2019, lights work no brake, the problem was a blown fuse. Others have had other issues which were corrected by having the sam re-calibrated. I don't understand, you said no brake signal but your rv towing is fine. Like Rapidoxidation said it is a smart system, nothing is active until you plug into the socket on the hitch
Do a "trailer wiring" search, lots will pop up. The sam reset usually has to with the issues involved in adding a hitch. There were issues with earlier MB's and newer Trailers but that has all been resolved by MB.
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