Blue Ox 2013 Dinghy Towing Guide - Manual (Page 25)

and motorhomes. Some models are wired to
supply turn-signal power to the same bulbs
that are used for the brakelights (commonly
referred to as a 4-wire system), while others
use separate amber bulbs for the rear turn
signals (a 5-wire system). Note that 4- and
5-wire systems are used on both motorhomes
and cars, so any one of four solutions may
be needed for any particular application.
Adapters are readily available to electronically
match the wiring systems of the dinghy and
motorhome.
The traditional method of wiring a dinghy
vehicle involves the use of steering diodes,
which function as one-way gates to the fl ow
of electricity, allowing power from either the
motorhome or vehicle to be supplied to the
rear bulbs. Because no electricity can fl ow
backward through a diode, it also prevents
power from the motorhome from being inad-
vertently introduced to any other circuits in the
dinghy vehicle.
Many late-model vehicles are equipped
with on-board diagnostics that continuously
check for proper operation of turn-signal and
brakelight bulbs. Unfortunately, the introduc-
tion of aftermarket steering diodes into the
vehicle’s wiring can “fool” this diagnostic
function, typically causing it to give false warn-
ings about burned-out bulbs.
For this reason, it’s common to modify each
of the vehicle’s tail-lamp assemblies to accept
a separate bulb. This bulb is then connected
Accessory kits such as this one from Demco include everything needed
for a safe hookup, including wiring kits, pins, locks, receptacles — and
a cover to keep the tow bar protected from the elements.
Above: Adding large rubber fl aps at the rear of a motor-
home, such as these from Blue Ox, will minimize
towed-vehicle damage from debris, dirt and grime
kicked up by coach tires. Below: The KarGard shield,
from Blue Ox, attaches to the tow bar and adds yet
another level of
dinghy protection,
guarding against
potential damage
from road debris.
directly to the motorhome, eliminating any
connections to the vehicle’s existing wiring
harness. This modifi cation usually involves
drilling a large hole in the tail-lamp refl ector.
Fortunately, special snap-in sockets are avail-
able that make this job somewhat easier. Since
the new socket takes up considerable space
behind the lamp assembly, care must be taken
in selecting a location for the new hole that
avoids socket interference with any other ob-
jects behind it.
Note that most states allow the turn signals
to be either red or amber in color, but only
permit the brakelights to be red. Thus, on au-
tomobiles equipped with amber turn signals,
the new socket is typically installed behind the
red brake-lamp lens.
In situations where modifi cations to the
dinghy’s original wiring either aren’t desirable
or practical, a set of removable towing lights
often provides a workable solution. Most
of these products are affi xed with magnets,
although some models can be equipped with
suction cups or hook-and-loop fasteners (ideal
for use on plastic or fi berglass surfaces). A
cable is then snaked across the vehicle to the
connector at the motorhome hitch receiver.
In some cases, the cable is semipermanently
routed inside or underneath the vehicle, allow-
ing the lights to be quickly removed and stowed
inside the trunk. Several companies offer wire-
less, removable towing lights, thereby eliminat-
ing the need for this cable altogether.
Although many motorhomes come with
a factory-installed 4- or 5-pin connector,
there are situations where a different connec-
tor is necessary. Some unapproved dinghies
equipped with an automatic transmission must
also be equipped with an electric lube pump,
which requires a connector pin for 12-volt DC
power (and ideally, a separate connector pin
for ground, in order to avoid drawing exces-
sive current through the existing one). Also,
some auxiliary braking systems require con-
nections to the motorhome, further increasing
the connector-pin count.
Ideally, the industry-standard connection
scheme should be observed when installing
this new connector, so that it can also be used
when towing boats, ATVs, horse trailers, etc.
Unfortunately, since no industrywide
standard exists for wire color codes used in
automobiles, another hurdle in dinghy wiring
involves identifying the proper wires for the
stop, turn and tail lamps (as well as a suit-
able ground connection). If you’ve had the
foresight to purchase a service manual for
your particular vehicle, this can sometimes be
accomplished by visual inspection of the wire
harness. More often than not, it involves con-
necting a test light to each suspected wire in
order to match it with the corresponding bulb.
Note that on 4-wire systems, the same wire
may be “hot” when either the brake or one of
the turn signals is operated.
When splicing diodes or other connections
into the vehicle’s wiring harness, it is impor-
tant to use top-quality connectors or splices.
In order to prevent any chance of corrosion,
all connections should be waterproof. Heat-
shrink tubing works very well for this purpose,
as does self-vulcanizing plastic tape.

Hopkins nVision Tire
Pressure Monitoring
System keeps an eye on
motorhome and dinghy tire
air pressure. The wireless
system can be easily trans-
ferred between vehicles
and used in the dinghy
without the motorhome.
Plug receptacles added to the dinghy and coach allow easy hookup of an electrical connector for taillights, turn
signals and the supplemental braking system.
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