Brake Controller Issues - Blowing a Fuse
Thread Starter
Newbie
Joined: Sep 2023
Posts: 2
Likes: 0
2017 GLS 550
Brake Controller Issues - Blowing a Fuse
Hi all - I’m trying to get my new-to-me 2017 GLS550 ready to tow. I’ve read a lot of the threads here (very helpful) and bought a Tekonsha P3. I bought the plug and play wiring harness… the one for this car is backordered so we did get the one for the Mercedes sprinter (3063-p), but from photos it appears the same, just a longer lead. We got everything seemingly hooked up. The harness clicks in perfectly.
Hooked up the trailer and nothing. Went in the fuse box and it’s blowing fuse 124.
Thought the harness or the controller might be bad. Reordered both. Reinstalled. Same issue.
Any thoughts?
Hooked up the trailer and nothing. Went in the fuse box and it’s blowing fuse 124.
Thought the harness or the controller might be bad. Reordered both. Reinstalled. Same issue.
Any thoughts?
MBWorld Fanatic!
Joined: Jun 2021
Posts: 1,928
Likes: 523
From: New Hampsha
'17 GLS450, '14 GLK250, Grandpa's Roadster
First thing I would do is unplug everything and see if the fuse blows. If not, start plugging things in one at a time and find out how far you have to go to get it to blow. If it's the trailer, see if you can isolate the position lights, brake lights and brakes.
Also, confirm the pin-outs for the Sprinter are the same as the GLS...
Also, confirm the pin-outs for the Sprinter are the same as the GLS...
Thread Starter
Newbie
Joined: Sep 2023
Posts: 2
Likes: 0
2017 GLS 550
Thanks @John CC We haven’t even gotten as far as plugging in the trailer. This is just happening when we plug in the Controller.… we were thinking about trying hard wiring it next?
Last edited by Seesportjump; Sep 8, 2023 at 12:40 PM.
Member
Joined: Jul 2015
Posts: 139
Likes: 36
2017 GLS 550
I had the same exact problem, the issue is that cable for the Sprinter. It's wired differently than the other Mercedes one which works perfectly fine. I guess you could try re-pinning the cable's terminations if you really want?
