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Trailer wiring

 
Old 04-22-2019, 10:40 AM
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GLS450
Trailer wiring

Hi. just recently purchased a 2017 GLS450 that has a factory hitch installed. or at least I think it is factory. What is missing however is the trailer wiring. There is no connector for the trailer wiring. Does anyone have experience with installing a wiring kit? Thanks for your help.
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Old 04-22-2019, 08:10 PM
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GLS550
Originally Posted by jpmoylan View Post
Hi. just recently purchased a 2017 GLS450 that has a factory hitch installed. or at least I think it is factory. What is missing however is the trailer wiring. There is no connector for the trailer wiring. Does anyone have experience with installing a wiring kit? Thanks for your help.
I do not know how true the following is. I went to my MB dealer last week to get a trailer hitch attached, so I could tow a trailer home with my daughter's apartment posessions. I have a 2018 GLS 550. They quoted me $5,000.00.
They told me the interior has to be rmoved to completely wire back from the dash to the hitch. That is MB does not prewire for the hitch like Ford, GM do. I said forget it.

Lee
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Old 04-24-2019, 12:51 PM
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2019 GLS450
Originally Posted by jpmoylan View Post
Hi. just recently purchased a 2017 GLS450 that has a factory hitch installed. or at least I think it is factory. What is missing however is the trailer wiring. There is no connector for the trailer wiring. Does anyone have experience with installing a wiring kit? Thanks for your help.
Look on your window sticker. The hitch is <$600 option from the factory. If it is on your sticker, you already have all of the hardware, software, and wiring installed.

Originally Posted by BLM2 View Post
I do not know how true the following is. I went to my MB dealer last week to get a trailer hitch attached, so I could tow a trailer home with my daughter's apartment posessions. I have a 2018 GLS 550. They quoted me $5,000.00.
They told me the interior has to be rmoved to completely wire back from the dash to the hitch. That is MB does not prewire for the hitch like Ford, GM do. I said forget it.

Lee
If the hitch was not factory installed, then what you were told is true. The dollar amount may vary by dealer depending on their labor rate, but it does involve the wiring, tearing apart the interior, replacing a module, and also software updates. Depending on the weight of the trailer you're looking to tow, there's other alternatives from Curt and also Uhaul.

Last edited by skw; 04-27-2019 at 08:16 AM.
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Old 04-26-2019, 06:25 PM
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1st - if you are in the US - basic trailer wiring can be installed with U-Haul for under $100 which gives you lights and brakes which uses a small relay box (normally Modulite) and splices into rear wiring.

2nd - the "factory" trailer hitch wiring which connects to the full car system is much more extensive - and can take up to 8hrs (or more) of shop time at the dealership.

For normal towing the clip-in wiring is fine - for heavy towing you can add a Wireless Brake Controller.

Mercedes has extensive features that are connected with the factory installed hitch system - to retrofit/add those connections is a real pain - there is a MB "harness" but the techs need NetStar access to see the wire diagrams - but still like 8hrs+ shop time.
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