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Double towing - Special wiring?

Mondegreen
Explorer
Explorer
I have a 5th wheel and have installed a hitch for double towing behind the 5th wheel. In order to get the lights on the utility trailer behind the RV, I ran the wires past the RV to the 4 terminal flat service plug on the back of my F-350. That works but it seems to be interfering with my trailer brakes on the RV. Indications are the brakes are working but not very well. Is there a wiring concern with both the RV and the utility trailer being plugged in? BTW, the total weight of the small trailer is 1100 lbs.
17 REPLIES 17

carringb
Explorer
Explorer
FWIW - I adjust my trailer brakes between full and empty water. It's only 830 pounds but I can feel it braking. 12.5 when empty (or they are grabby) and 14v when water is full. My trailer is pretty much as the limits of its tandem 6k axles though. I'll swap to disc brakes later if the trailer proves to be reliable enough.
2000 Ford E450 V10 VAN! 450,000+ miles
2014 ORV really big trailer
2015 Ford Focus ST

Mondegreen
Explorer
Explorer
All I could afford wrote:
Have you tried towing the whole combination with out the rear trailer wiring connected to eliminate the possibility of an electrical interference issue? If you still feel the reduced braking ability,I would have to assume it is just due to the extra weight pushing your fifth wheel trailer


Not yet but I plan to do that. When time allows. Good idea BTW.

All_I_could_aff
Explorer
Explorer
Have you tried towing the whole combination with out the rear trailer wiring connected to eliminate the possibility of an electrical interference issue? If you still feel the reduced braking ability,I would have to assume it is just due to the extra weight pushing your fifth wheel trailer
1999 R-Vision Trail Light B17 hybrid
2006 Explorer Eddie Bauer
2002 Xterra rollinโ€™ on 33โ€™s
1993 Chevy Z24 Convertible
Lives in garage 71,000 miles

Bionic_Man
Explorer
Explorer
Bedlam wrote:
Bionic Man wrote:

As a point of reference, I tow up to 5100 pounds behind my 5er, and I only make a minor adjustment to my trailer brake control (like up by 1 or 1.5 when towing my boat).

Your boat trailer probably has surge brakes. The utility trailer does not and relies on the FW and vehicle braking.


Yes the boat trailer has surge brakes. I also tow either a small (16') boat or tandem axle 14' utility trailer with two atvs. When I do that, I don't need to adjust trailer brake controller at all.
2012 RAM 3500 Laramie Longhorn DRW CC 4x4 Max Tow, Cummins HO, 60 gallon RDS aux fuel tank, Reese 18k Elite hitch
2003 Dodge Ram 3500 QC SB 4x4 Cummins HO NV5600 with Smarty JR, Jacobs EB (sold)
2002 Gulf Stream Sea Hawk 29FRB with Honda EV6010

Bedlam
Moderator
Moderator
Bionic Man wrote:

As a point of reference, I tow up to 5100 pounds behind my 5er, and I only make a minor adjustment to my trailer brake control (like up by 1 or 1.5 when towing my boat).

Your boat trailer probably has surge brakes. The utility trailer does not and relies on the FW and vehicle braking.

Host Mammoth 11.5 on Ram 5500 HD

Mondegreen
Explorer
Explorer
mkirsch wrote:
Do your brakes work better without the second trailer plugged in?


Yes. I think that I expected little effect from the additional weight, so I did not adjust the brakes up enough.

Mondegreen
Explorer
Explorer
Bionic Man wrote:
........I don't understand how you wired for the 2nd trailer. Did you somehow go all the way up to the tow vehicle?

ANS: Yes I should have tapped the RV taillights but I wanted it to connect as close to the source as possible. So I routed the wire all the way to the rear of the truck.

I almost always tow tandem. The lights for my 2nd trailer are just wired off the tail lights on the 5er, and they work fine.

As a point of reference, I tow up to 5100 pounds behind my 5er, and I only make a minor adjustment to my trailer brake control (like up by 1 or 1.5 when towing my boat).

ANS: OK that is good to know. Adding 1-1.5 on the brake controller for the boat trailer lets me know something.

Brisk
Explorer II
Explorer II
I spliced the 4 pin flat into the 5er taillights and have never had any issues.
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Toyhauler-'06 Forest River Sierra Sport F32

2001 Malibu Sunsetter VLX Wakeboat

Bionic_Man
Explorer
Explorer
I'm probably a little dense, but I don't understand how you wired for the 2nd trailer. Did you somehow go all the way up to the tow vehicle?

I almost always tow tandem. The lights for my 2nd trailer are just wired off the tail lights on the 5er, and they work fine.

As a point of reference, I tow up to 5100 pounds behind my 5er, and I only make a minor adjustment to my trailer brake control (like up by 1 or 1.5 when towing my boat).
2012 RAM 3500 Laramie Longhorn DRW CC 4x4 Max Tow, Cummins HO, 60 gallon RDS aux fuel tank, Reese 18k Elite hitch
2003 Dodge Ram 3500 QC SB 4x4 Cummins HO NV5600 with Smarty JR, Jacobs EB (sold)
2002 Gulf Stream Sea Hawk 29FRB with Honda EV6010

nevadanick
Explorer
Explorer
Thats how i connected my Ford for doubles and it was not a problem.

Mondegreen
Explorer
Explorer
Wonderful feedback. Thanks. I think I have some checking to do. Out of all that experience, I will find the culprit. It might be that the added weight has caused considerable more brake level input than I expected. But having the assurance that my hookup is not in itself, a problem, helps. I'll check and report.

carringb
Explorer
Explorer
I would be suspicious of the ground being overloaded, since that would be the only common circuit with the brakes the and lights of the 2nd trailer. A short to ground anywhere in the 2nd trailer can also cause braking problems.

Also, are you sure you just aren't feeling the push of the extra trailer weight?
2000 Ford E450 V10 VAN! 450,000+ miles
2014 ORV really big trailer
2015 Ford Focus ST

Bedlam
Moderator
Moderator
I'm thinking the extra weight of the second trailer is affecting brake performance. I cannot see how the light connections would make a difference.

Host Mammoth 11.5 on Ram 5500 HD

mkirsch
Nomad II
Nomad II
Do your brakes work better without the second trailer plugged in?

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