Installing Backup Lights

I would check with the local DOT/DMV to see if your BACK-UP lights are the approved type. Here in Virginia we have a bunch of laws around this and in my case I ended up a couple of times having to remove things in front of the Safety Inspection bunch before they will put a Safety sticker on my trailer haha...

They certainly did not like my switchable back up lights - had to come on when my truck went into REVERSE... After I removed them then i mounted them on the rear side of the trailer and actually got better results looking back from the truck.

The Safety Bunch here really watches what goes on the back and front of the road vehicles and trailers (in my case) here...


Roy Ken

Retired EE here. For three amps I wouldn't (and didn't) use a relay for b/u lamps. As Mex indicated, even if there were a decent voltage drop the lights would be just as bright. But with 14awg wires you will not have any significant Vdrop.
Mine have been wired that way for at least 5 years and work great.

I would use a relay. Power the contacts off the trailer battery(ies) and use the TV as the control.
Amperage seems high. What is make and model of proposed lights?

Check that ad carefully. Many 18-watt lights are manufactured with CREE chips and they use a voltage regulator that allows the same brightness from 10-30 volts.

At 12.0 volts none of the dozens (not an exaggeration) that I purchased drew more than 1.1 amperes. The amperage is rated at 10 volts.

You will do fine with what you propose. I smudge a little silicone grease around the grommet for the wires.

I always use a relay when adding backup lights, be it to the TV or the 5er. I just find it simpler in the long run.

A relay is needed if the 3 amps will overload the circuit.
Otherwise no.