DIY Emergency Flasher Unit for trailers

[RoyBraddy]

I may have my attached photo working now...

I haven't done this but have heard you can plug a heavy duty flasher unit into the RV Trailer cable end and it will flash the RV Trailer RUNNING LIGHTS...



Roy Ken

[Sbrinson]

A recent series of exchanges in these forums touched briefly on safety problems that might be experienced if a trailer became disabled on the roadside, especially at night. Normal procedures would be to move as far off the road as possible, turn on emergency flashers and put out emergency reflector triangles. Of concern was how to improve visibility of the trailer should it become necessary to disconnect the towing vehicle in order to leave the scene to obtain parts or assistance, which would deprive the trailer the benefit of the tow vehicle’s emergency flasher system.

A couple of posters mentioned some suggestions for systems that could provide a method of having the trailer’s running lights illuminated while the tow vehicle was disconnected. Another poster said he had built a system that would incorporate a flasher. I don’t recall seeing more details of that system, but the basic idea seemed like a valid safety addition to pursue. I thought it might be practicable to incorporate the needed components into-- and on-- a 7-Pin connector, such as would normally be mounted on a tow vehicle. This would provide flasher capability for the trailer by plugging its’ 7-pin plug into the flasher module. Components are available at most auto supply stores, and will cost about $35.
Supplies include:
(a) an electronic (or thermal) flasher unit, capable of supporting multiple lamps.
(b) a 3-pin headlight socket with pigtails (for the flasher).
(c) a single-pole double-throw toggle switch (20 amp or better rated).
(d) an automotive fuse holder with fuse (capacity dependent on number and types of
tail and running lights—LED’s draw less amperage).
(e) epoxy cement, electrical tape and hookup wire.
(f) tools include soldering iron and solder, drill and bits, file, forceps or long tweezers wire stripper, diagonal cutter and a phillips-head screwdriver.
Procedural notes:
* drilling holes in the plastic body of the connector shell can result in melting the plastic
if drill speed and pressure are too high. For larger holes (7/16” for the switch) start
with a smaller size and increase incrementally.
* use wire capable of handling the amperage of your running light load.
https://www.thespruce.com/matching-wire ... ge-1152865
It is suggested that all wire ends are tinned (with solder).
* using a strip of duct tape or gaffer tape to hold the connector’s weather flap in
the open position makes assembly easier.
* estimate wire lengths and pre-assemble items before inserting into the connector shell.
* avoid excessive wire lengths, (but leave enough slack to insert the switch) and avoid
tangling the wires.
* unscrewing and removing the unused center contact from the connector’s insert will
provide more internal clearance for the switch and for carefully positioning the wires
when re-installing the connector’s insert.
* I used a file to round off and slightly reduce the size of the switch’s toggle, in order to
improve clearance to get it inside the connector shell. I also filed a flat spot on the
outside of the shell where the switch was mounted, so the threaded mounting ring
has better purchase on the switch neck.

Start by removing the connector’s insert by unscrewing the Phillips locking screws on either side of the connector shell. Note the position of the keyway on the bottom of the insert and the key on the inside of the connector shell. This will aid re-assembly. I also removed the rubber sleeve portion of the cable clamp.

Drill the 7/16” hole for mounting the toggle switch. Check inside the shell to ensure the switch will clear the cable clamp area. (See Photos.) On the same plane, drill a small hole (approx, 3/16”) oriented 90 degrees from the switch hole.

The fuse holder will be mounted on the outside of the connector shell to facilitate changing fuses when necessary. Feed both wires from the fuse holder in through the small hole. One wire is connected to the insert’s pin #1 (+12 VDC). The other is soldered to the center tap of the single-pole double-throw toggle-switch. One side of the switch is routed directly to the insert’s pin #6 (running lights). (See diagrams.)

Now, feed the headlight socket’s three wires into the rear of the connector shell through what would normally be the cable entry. The wire that will connect to the electronic flasher’s 12 volt input pin is soldered to the remaining tap on the toggle switch.
The headlight socket wire that will connect to the “load” pin of the flasher is also wired to pin #6. The headlight socket wire that connects to the “ground” pin of the flasher is wired to insert’s pin #4 (-12 VDC). This arrangement enables flipping the switch to one side to utilize the flasher, or to the other side to turn on the running lights so they burn constantly.

Double check all wiring and proceed to assemble. Install the switch, using forceps or long tweezers to aid in inserting the switch neck into the 7/16” hole. Dress the internal wiring so it isn’t crimped or caught between the shell and the insert. Turning the insert will help coil the internal wires so they take up less space. Align the keyway slot on the insert with the key on the interior bottom of the connector shell. Press the insert so that it achieves sufficient depth in the connector shell, then re-install the Phillips screws to hold the insert in position,

Carefully feed any slack in the headlight socket wires into the back of the shell and press the socket to the rear surface of the connector shell and epoxy in place. After the epoxy hardens, use electrical tape to mount the fuse holder to the side of the shell. Insert the fuse in the fuse holder, and carefully install the flasher into the headlight socket.

Notes: Turn signals and brake lights are not utilized by this module. It controls only the tail and running lights. Also, a rear-view video camera that is powered by the running lights circuit will be subjected to the on/off cycles of the flasher.