Double towing - Special wiring?

[Mondegreen]

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.

[carringb]

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.

[Mondegreen]

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]

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

[Bionic_Man]

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.

[Bedlam]

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.

[Mondegreen]

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]

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]

I spliced the 4 pin flat into the 5er taillights and have never had any issues.

[Bionic_Man]

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).

[nevadanick]

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

[Mondegreen]

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]

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?

[Bedlam]

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.

[mkirsch]

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