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Wiring Brakes and Lights on Our Custom Tiny House Trailer

Wiring Brakes and Lights on Our Custom Tiny House Trailer

7/18/14 (4 years ago)

Wiring Brakes and Lights on Our Custom Tiny House Trailer

Since our trailer can be towed with a pickup truck or a semi tractor, we wanted to wire it for both flat pin RV-style connectors and round pin heavy duty connectors. This was a little tricky, since RV connectors combine brake and stop lights into one pin each for right and one left lamps. HD connectors have separate pins for left turn signal, right turn signal, and brake lights. So we used two sets of brake/turn lamps. The RV connector uses one set and the HD connector uses the other set. The clearance/running light pin runs both sets. That way, no special wiring with diodes was required. We also made a long cable with RV connectors on both ends to hook up to the tow vehicle.

Not everyone follows the "standard" way of wiring trailer lights. In fact, when you search for wiring diagrams on the Web, you find several different ways to do things. So, we connected everything to DIN wiring blocks to allow us to easily change the wiring configuration if needed.

Our state laws require electric brakes for trailers over 3,000 lbs, so all four wheels have electric brakes. These are run by a brake controller in the cab of the towing vehicle. State law also requires a safety breakaway switch that will activate the electric trailer brakes in case the trailer is separated from the tow vehicle. We bought a rechargeable, battery-powered breakaway switch and installed in the trailer frame above the dolly so it could be used in both tow configurations.

How We Did It

We started by planning out the wiring on a dry erase board. Then we made a test panel on a piece of plywood with the actual connectors and lamps and made sure everything worked. Then we created a complete wiring diagram PDF.

Next, we drilled holes in the frame for the wiring block access boxes. The plasma cutter came in handy for cutting the large openings for the tail lamps. Once the holes were in place, we installed metal conduit along with the retainer brackets, junction boxes, and flexible metal tube. It took a little while to snake the wires through the conduit (with the help of a little liquid dish soap). Then we soldered the lamps. We used heat shrink tube instead of electrical tape just to be a little more professional.

DIN blocks made wiring much easier. We soldered all the ends of the wires so they wouldn't fray and hooked them up to the appropriate slot in the block. The front connector had 27 wires, so it was a little tricky getting them all lined up and fitting the block into the tube. But it sure looked nice when it was done. The rear block only had 17 wires, so it was a little easier. It's surprising how complicated the wiring is for just a few lights.

We found a place for the breakaway switch at the front of the trailer above the dolly and drilled and tapped holes and bolted it in. We used 4-pin trailer connectors so the unit could be detached easily later if needed.

Once we had everything in place, we tested it to make sure all the lights and brakes actually worked. We used a 12V battery and alligator clips and tested each connector pin to see if the right lights came on, the breakaway switch battery would charge, and the electric brakes and breakaway switch would activate properly.

Everything worked! Now we were ready for a road test.

Materials

  • Metal conduit, brackets, junctions, and boxes
  • Wire
  • Rechargeable battery-powered breakaway safety switch kit
  • Lights (round red and amber, red 2-way tail lamps, license plate lamp)
  • Connectors (RV and HD)
  • DIN blocks
  • Heat shrink tube
  • Metal flex tube

Tools

  • Electric hand drill
  • Plasma cutter
  • Hand grinder
  • Gas soldering iron
  • Wire cutters
  • Screwdrivers
  • Wrenches for conduit

More Information

  • RV and HD style connectors RV and HD style connectors
  • Installing the front wiring block Installing the front wiring block
  • DIN wiring block DIN wiring block