No Power to Trailer battery

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

winesalot

Junior Member
Joined
Feb 11, 2019
Posts
23
Reaction score
10
Location
Chelan, WA
Ram Year
2001
Engine
5.9 Cummins
I have a gooseneck trailer that has electric over hydraulic brakes. The hydraulic pump requires the 12V hot wire to work and it is not energized. I checked the 40 amp fuse under the hood and swapped the trailer power relay with the blower relay. Still no power at the truck side of the plug. Any Idea what has failed?

What triggers the relay to close?
 
OP
OP
W

winesalot

Junior Member
Joined
Feb 11, 2019
Posts
23
Reaction score
10
Location
Chelan, WA
Ram Year
2001
Engine
5.9 Cummins
OK, I figured out that the connection under the rear end where the stock harness terminates and the bumper/gooseneck adapter are butt connected had a corroded hot wire.

I would still love a wiring diagram for the trailer's wiring for future diagnosis.
 

crash68

ACME product engineer
Staff member
Administrator
Supporting Member
Joined
Mar 20, 2016
Posts
11,370
Reaction score
18,463
Ram Year
2015
Engine
3.0 EcoDiesel
What triggers the relay to close?
The trailer 7-pin +12V doesn't have a relay that energizes it, it a straight connection to the battery via the fuse.
The trailer plug light circuits do have relays, the are before fuses, you need to have the lights activated to be able to check voltage at the fuses.

If that plug for the gooseneck at the rear bumper wasn't a moulded t-tap fitting that plugs into the back of the 7-pin on the bumper, it's most likely an aftermarket setup
 

Tulecreeper

Senior Member
Military
Joined
May 27, 2023
Posts
2,213
Reaction score
2,706
Location
AZ - 83 Miles SW of the Geographical Center
Ram Year
2023
Engine
6.4 Hemi
OK, I figured out that the connection under the rear end where the stock harness terminates and the bumper/gooseneck adapter are butt connected had a corroded hot wire.

I would still love a wiring diagram for the trailer's wiring for future diagnosis.
Looking at the back of the truck:TruckWiringDaig.png
 

Latest posts

Forum statistics

Threads
202,579
Posts
2,955,296
Members
167,415
Latest member
Agimpuraj
Top