How to Power Trailer Lights from the Reverse Circuit and the Trailer Battery w/out Back Feed
Updated 03/05/2026 | Published 02/26/2026
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Question:
I have an enclosed trailer with exterior cargo lights that were operated by an interior switch which is powered from a battery inside my trailer. I disconnected the switch from the cargo lights and I wired the cargo lights to my reverse lights that pulls power from truck 7 way plug. I I would like to hook the switch back up so I can operate the lights from the interior switch trailer battery but also leave them wired to the reverse lights 7 way plug . Can I use the RM790 diode wired in line to make sure one power source does not back feed to the other? Would I need one on each power source? Any on grounds? Thanks
asked by: Michael H
Expert Reply:
You sure can Mike. You would need to wire both the reverse light circuit and the switched power source to the input side of the Hy-Power Diode item # RM-790 and then the output side to the circuit with the lights.
The item # RM-790 diode will keep the switched power from back feeding onto your Silverado's reverse lights. You would only need to run an additional ground if your battery for the lights is not grounded to the trailer frame.
Do you have a circuit breaker between your battery and the lights? If not I recommend adding one like item # 9506P before the battery.
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Michael H.
3/5/2026
I do have everything powered through a fuse block for the trailer. I set my trailer up so all the12v devices are stand alone off of a lithium ion battery dedicated to the trailer. The rear cargo lights are grounded to the frame because of being powered by 7 way plug. Yes, I will have to ground the cargo lights to the dedicated trailer battery as well. With that being said, should I install another rm-790 on the ground circuit as well? Thanks
Product Page this Question was Asked From
Roadmaster Hy-Power Diode - (Qty 1)
- Accessories and Parts
- Flat Tow Wiring Harness
- Diodes
- Roadmaster
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Hello J.
3/2/2026
When I have done this in the past for a customer I install a switch on the trailer so that the backup light can be turned on with the trailer battery. Depending on how the customer is using that I will install a Bosch relay to lower wire load on the PU wires. ( flood light ) note that with LED that problem is going away.