Troubleshooting the 7-Way RV Upgrade Kit for Trailer Brake Controller Installation

Updated 09/03/2025 | Published 06/29/2025

Products Featured in This Question

7-Way RV Upgrade Kit for Trailer Brake Controller Installation - 12 Gauge Wires

(386)

$97.59

40 Amp In-Line Circuit Breaker - Perpendicular Mount Bracket

(100)

$9.96

Hook Probe Circuit Tester

(66)

$13.14

Question:

Hello. We installed this kit on my 2018 Subaru Outback last spring and it was working great until today. Camped in a few rain storms over the weekend, started it up to heat hike and the lights and breaks worked great, stopped for coffee, then when we turned the car back on, the campers lights didn’t work at all no running lights, brake lights, turn signals, etc. For some background info, u-haul installed my hitch and 4-pin wiring, we bought this Kit afterwards to run power green the battery to the 7-pin for the camper breaks. So when we got it home, we used a voltmeter to check the 4-pin and there’s no power going to it. We’re suspecting possibly the circuit breaker that came with the kit has blown? Where do we go from here? Is there a way to flip the breaker back on? It do we need to purchase a completely new breaker? Thanks for your help!

asked by: Dani C

Expert Reply:

Hey Dani. Did you check the fuses related to towing functions on your Subaru?

If your fuses are all good, then you will want to move to the 7-way trailer connector item # ETBC7L. Using a circuit tester like item # PTW2993, check the black wire on the back of the 7-way way while the vehicle is running. If you are getting power here then the problem is in the trailer connector, and it will need to be replaced.
If you are not getting power in this location, then you will need to begin tracing the black wire back as far as you can while checking for breaks or frays.

Not sure what connector U-haul installed but did you check the wires running to where it plugs into the item # ETBC7L to see if they had power?

Before you attempt to replace the 40 Amp In-Line Circuit Breaker item # 9510, I would use a circuit tester to see if that wire from the battery has power leading up to it.

expert reply by: Jerred H

Jerred H.

9/2/2025

Hey Dani, did you have a chance to check the fuses on your Subaru and test the wires as suggested? I'm eager to know how it turned out, as it could help others facing similar issues with their setup.

Dani C.

9/3/2025

@JerredH we did get the issue resolved! We confirmed with a circuit tester that power was correctly coming out of the battery and that it was showing zero down at the 7-pin. It turns out that the adapter that u-haul installed had a 10am fuse that they put behind the side wall in my trunk and didn’t inform me of. We ended up replacing this blown fuse and splicing the wires off the adapter in order to extend them outside the paneling for easier access if it blows again. So no issue with the 7-way kit we purchased from etrailer. Thank you!