How to find reversing wires to trigger or power backup camera systems.
We recommend that you wire up the triggers as the last part of your installation (after the systems monitor
has been wired) this is so that you can use the system as a safe way to test for a reversing wire.
Back up camera systems (reversing camera systems) require a signal to “Trigger” the system into action
so that it automatically operates when the vehicle is in reverse.
Whilst some systems are designed to allow cameras to operate even when the vehicle is not in reverse it
is still necessary to wire a trigger system in so that the Camera that is facing backward automatically turns
and or takes over as priority when in the vehicle is in reverse.
When wired in correctly using the right trigger priority, the system can also automatically turn on the rear
camera of an attached trailer taking priority over the vehicles back up camera when the trailer is
connected.
The most common way to trigger the rear facing camera is to use the + wire that powers one of the
vehicles reversing globes at the back of the vehicle.
NOTE: Some vehicles that Use CAN bus to operate rear lighting systems may require additional parts to
trigger the system.
Caution: Never test for reversing wires standing at the back of the vehicle, with the engine running and the
gearbox in reverse gear. If the car/truck can not be placed in reverse without the engine running, Special
procedures should be employed. In this case we highly recommend you seek a professional installer to do
this type of work. Failure to follow proper procedure could cause serious injury or death. (The vehicle could
back over you)
Step 1.
Place the car in reverse, with ignition on but the car not running (do not leave the cars ignition on for long
periods of time without starting it) observe or have an observer notice which light turns on and its location
in the lens. Turn the ignition off. Then, locate the globe socket that holds the reversing globe into the lens.
In some cases the Lens has to be removed from the car to expose the socket. In most cases however, you
can gain access from the inside of the car behind a removable interior wall/panel.
Step 2.
Identify which wire is the globes ground and which is positive (see Fig 1 diagram). Light globes have very
low resistance so if a globe is in place, both wires will show up as a ground. Even if you remove the globe
the second globe on the other side of the vehicle will still give the positive side a short path to ground and
may still be indistinguishable from the globes earth. For this reason it is necessary to energize the globe to
find out which side is positive and which side is negative.
Using a multimeter set to DC volts (make sure that it is on the correct scale) attach the negative probe to
one of the globes wires and the positive probe to the other (in most cases
you can push the probe ends into the back of the globe socket) if not, you may have to
carefully strip both wires sheaths back to expose the wires core making sure you keep them separate
and away from the cars chassis to avoid any shorts). You should also make sure the globe it self is
not resting on something that could be harmed by extreme heat as the globe when on can get very
hot). Turn the ignition back on again with the cars gear set to reverse (without the engine running).
The globe should illuminate and the multimeter will show a positive voltage or a negative voltage
across the globe. By noting whether the voltage is positive or negative you can define which wire is
positive or negative. If the reading is positive then the probes positive is connected to the positive
wire. If it’s a negative reading then the multimeter's negative probe is connected to the positive wire of
the globe as a final check, take the vehicle out of reverse with the ignition still on and check that the
voltage is now zero.
If the vehicle can not be placed in reverse without the engine running the following procedure should
be used. With the car off, remove the globe. Set your multimeter to resistance on the lowest setting.
Place one probe on a part of the chassis that is ground (most rear tail light assemblies have a small
grounding screw close by). If you can not find one look for some exposed chassis (like a tailgate hinge
etc). Measure the resistance to ground of both wires in the back of the globe socket (with the globe
out) whist the resistance will be very similar (because of the other globe still in the circuit) one wire will
have a slightly higher resistance. The one with the highest resistance should be the positive wire.
Connect the system to this wire and then use the reversing system to test if it is triggering.
With no one at the rear of the vehicle. Start the car. Make sure the reversing systems monitor is in the
off state and then place the vehicle in reverse. If you have found the correct wire the system will
automatically turn on from its off state. If you have connected the trigger to the globes earth no harm
is caused but the system will not trigger. In that case simply connect it to the alternate wire and
repeat.
CAN BUS
In the event that the cars reversing lights are driven by CAN BUS the above wiring system may not
trigger the system correctly. It may even create a globe fault warning. In this case a CAN BUS module
(sold separately) may need to be installed. However, just because the vehicle has a CAN BUS system
does not necessarily mean that it will require such a module to work. In fact the opposite is true. Most
vehicles do not require an additional module. If a CAN BUS module is required we recommend
seeking advice from a professional installer.
Multi trigger systems. Please refer to the diagram provided with trailer trigger systems. Pay special
attention to the AV camera numbers and trigger numbers. It is important that the AV camera numbers
match the diagrams placement in order to provide the correct priorities so that when a trailer is
connected it takes rear view priority over the vehicles rear view camera and so that when no trailer is
connected the vehicles rear camera operates automatically.
P7
P8
