All about Vehicle wiring

(written by Sue Monroe)

Wiring A Vehicle - Many newer vehicles have wiring for towing directly from the
factory.  However, some don’t and then you will have to add wiring to your vehicle.  In
most places it is the law to have lights on your trailer during the day as well as at night.
Today’s vehicles have complex wiring systems and there are T-connectors that are
available for easier installation.  Some vehicles require converters or power converters.  It
is best to have experts install your wiring because some vehicles have low amperage
systems.  You must also determine if you have a 2-wire system or a 3-wire system, and
some multiplexed vehicles are not to be cut or spliced into.  So, it is better to have it
installed professionally.

What type of wiring you will need depends on what you are towing.  Some smaller
trailers require only a 4 way wire plug which is for stop, turn and taillights.  There is also
a 5-way wire connector, which will enable to trigger surge brake lock out automatically
when backing up or back up lights.  This is especially common on boat trailers and is
getting more popular.  Larger trailers require a brake controller.  A brake controller is a
device that is installed in your tow vehicle and an electronic signal is sent to the trailer
telling it to put the brakes on.  This type of connector will require a 6-way or 7 -way plug.
The main purpose is to have the trailer stop at the same time that your vehicle does.
There are many different kinds of brake controllers on the market, depending on the
trailer weight and axles.

A 2-way wire system uses the same wire and bulb to illuminate both the brake light and
turn signal.  It can be easily identified by the use of a single bulb on each side of the
vehicle to light up the brake and turn signal.  A 2-way system will generally have red turn
and brake light lenses.

A 3-way light systems have separate wires for the brake and turn signal bulb.  They have
2 bulbs on each side, one for the brake lights and a separate for turn signals.  The 3-way
system will generally have amber turn signal lenses.  On a 3-way wire system, a taillight
converter is required.

If your vehicle requires a taillight converter, you now must choose the correct one.  Many
newer vehicles are only capable of handling the power need of the vehicle itself.  Some
trailers demand a large amount of power.  This is based on the number of lights installed
on the trailer.  Since electrical current is measured in amps, you must determine the total
amperage draw of a trailer, add the number of bulbs of each light and multiply by each
bulbs amperage rating.  Taillight/Brake bulbs are rated 2.1 amps each and marker lights
draw approximately 0.6 amps each.