This past summer I was tied up with several things, putting an engine in a friend’s car, fixing my generator, among other things like health issues.

But I accomplished one thing I wanted to do. After hauling a car dolly, and then 3 trailer loads of pellets, with half the lights out last spring, pulling over to let traffic pass before attempting a left turn, it was time to do something. But if I was gonna do it, I was going all out. I wanted amber turn signals, and my lower sidemarkers to flash in sync with the turn signals. Upper sidemarkers are clearance lights so they don’t flash.


DIY switchback module wiring (essentially a self powered delay off Bosch relay for super cheap). I got the idea from a Youtuber named Flyryde, but I elaborated on it a bit. This has SO many possibilities.

So I started with the trailer, first cutting openings for the additional amber lights with a hole saw and grinder. Then ripped out the factory scotchlocks and worthless grounds and other 1/2-donkey factory wiring, and redid it all with solder and heat shrink, wired my way. Repaired half of the sidemarkers and the license light which were corroded and nonfunctional. Put LEDs in the sidemarkers and ended up having to replace all the rear lights anyway by the time I was done, should have just went LED there too but oh well. Replaced the 3rd brake light I added when I first got the trailer 25 years ago.

Cleaned up all the rust in my front box I made back then, and addressed the leaks, and put all my new wiring in there. I went all out with terminal strips, the DIY switchback modules, and a converter with a switch if being towed with a vehicle with standard combined brake/turn wiring.


Control plate (not bolted down yet) with converter, switch, switchback relays on the back. Front relays are to prevent backfeed into converter, with less voltage drop than diodes. Additional switch holes for future uses.


Control box overview with terminal strips mounted on 1/2” thick UHMW strip. Brake actuator housing just sitting in there to check fit.


Control box closed, repainted, totally sealed this time.

Changed the Jeep connector to a 9 wire, which I also used way back then. Had gotten so tired of 7 wire RV plugs being wobbly and poor connection. Also gives a dedicated wire for my 3rd brake light. I already had adapters I made to go both ways from 4/7/9 and I have used them countless times over the last quarter century.

Since the 9 wire plug takes more force to plug in (it’s making a much better connection), I welded some gussets to stiffen the trailer connector bracket that bolts to the Jeep bumper.


Stiffened trailer connector bracket.

On the Jeep end, my converter had failed. So I bought a new one, but also added some switches. One to change the turn signal output from standard combined brake/turn from the converter (in case I’m towing something else), to direct from the Jeep amber turn signals. Nice clean direct path to the trailer lights with little voltage drop. In either case the 3rd brake light has its own wire.

The other switch to change the 12v+ charge line from always on, to switched with ignition, or totally off. My brake actuator sucks power all the time, so nice to have it switched. But also nice to kick it on to power the trailer interior dome light. Also nice to keep it off in case it gets salt in there. I’m also in the process of rebuilding the trailer brake actuator. At least the Jeep has strong brakes 100% recently new.


Switches and converter in the Jeep, stuffed into rear quarter. Ended up taking the switched with ignition signal from the rear wiper wiring. I left the interior free from carpet and plastic panels after the floor reconstruction, so all this is accessible.

It all works quite nicely. Here’s a link to a video of it working. Using hazards because it was quicker but turn signal would have been the same. You can see the rear lights reflecting in the door trim. Another plus, I get amber trailer hazards and the brake lights still function.

Dropbox Video
Switchback turn signal operation (hazards being used)


Finished, caught mid flash, all lights on!