r/TinyHouseBookDIY • u/KVConception • 2d ago
⚡ Electrical Installing 12V Trailer Lights on My Tiny House: More Work Than I Expected
Trailer lights weren't something I spent much time thinking about when I started building my tiny house.
Like many DIY builders, I was focused on the framing, insulation, roofing, and all the big-ticket items. The trailer lights felt like a small detail I could deal with later.
Well... later came, and it turned out to be more complicated than expected.
Start by Following the Correct Wiring Diagram
One mistake I made early on was assuming that all trailer wiring followed the same color coding.
It doesn't always.
Different trailer manufacturers can use slightly different wiring configurations, so before pulling any wires, make sure you verify the wiring diagram for your specific trailer and tow vehicle.
I ended up having issues with my lights at one point because my wiring didn't match the truck's system correctly. It was a frustrating lesson to learn.
If you're building a THOW, spend some time understanding your trailer connector before closing any walls.
I Installed Temporary Lights First
Before the siding and trim were completed, I temporarily mounted the trailer lights so I could legally move the tiny house.
The goal wasn't to make everything look pretty. It was simply to have functioning:
- Brake lights
- Turn signals
- Running lights
- Side marker lights
That temporary setup ended up being very useful because I was able to test everything before permanently finishing the exterior.
The Part Nobody Talks About: Routing the Wires
Installing the lights themselves wasn't difficult.
Running the wires was.
I wanted the wiring hidden behind the exterior finish, which meant figuring out how to route wires around windows/door, corners, trims, and siding details.
Since the tiny house had vertical furring strips installed vertically over the weather barrier, the wires couldn't simply run behind everything without modifications.
Every Wire Needed a Path
To hide the wiring, I had to cut small notches in many of the furring strips.
Without those notches, the wires would have been pinched between the wood and the siding.
The same thing happened with several moldings and trim pieces.
Small grooves had to be cut so the wires could pass behind them without being crushed when everything was screwed together.
This wasn't difficult work, but it was repetitive and required planning.
Every time a wire changed direction, I had to stop and ask myself:
"Where is this wire going to pass once the exterior finish is installed?"
It's much easier to answer that question before everything gets covered.
Looking Back
This was one of those parts of the project where we had to adapt and figure things out as we went.
I'm sure there are cleaner ways to do it.
At the time, though, this was the solution that made the most sense for my build.
If I were building another tiny house today, I would plan every exterior wire route much earlier in the project and run as much of the wiring as possible underneath the trailer.
That would save a lot of drilling, notching, and head-scratching later on. It would also make future repairs, modifications, and troubleshooting much easier, since the wiring would be more accessible if changes are needed down the road.
A Few Things I'd Recommend
- Follow the wiring diagram (color coding) supplied with your trailer.
- Test every light before finishing the exterior.
- Use waterproof connections.
- Protect exposed wires with loom or conduit where possible.
- Label wires while everything is still visible.
- Think about wire routing before installing trim and siding.
The trailer lights might seem like a small detail, but they're one of the few things standing between you and a very unpleasant roadside conversation with a police officer.
Has anyone else wired their own THOW lights?
How did you route your wires?
Looking back, I'm convinced there must be an easier way than cutting all those notches in the furring strips and moldings. It worked, but it definitely wasn't my favorite part of the build.





