Instructables

3 wire trailer light converter to 4 wire vehicle

Picture of 3 wire trailer light converter to 4 wire vehicle
This is how to make your own 3 wire trailer light + Ground converter to a 4 wire + Ground vehicle.  Are you confused about how these
epoxy filled electronic converter are made ?  I am shedding a little light on the subject here ( no pun in 10 did ).  I also made a utube
of this, but for those instructables fans, here is how I wired my 2010 Honda Civic to a Harbor Freight utility trailer.
 
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Step 1: This converter will require a pair of Radio Shack relays

Picture of This converter will require a pair of Radio Shack relays
This project requires the purchase of a pair of Single Throw Double Pole relays, I used the Radio Shack Mini Relays
as they can handle 10 amps and are 12 volts.  If you have a lot of trailer lights you will have to size the wire and relay
load to your need.  This instructable is more of a how I did rather than a how to.  I could not find any information
on the high price trailer light converter kits on the web, so this is how I think they work.

I have built this system on my new (at the time 2004 Honda Civic) and it has served me with no problem, to date.

Step 2: Pinout of relay

Picture of Pinout of relay
This is the pin out of the relay.  I cemented two of them with RTV together so that the coils of each were located in the upper left hand corner and it could be stuffed in a pill bottle to keep anything from shorting the system out while it is in the trunk.