Automotive electronic communication explained. O mark bruce Have you ever experienced an issue when hooking up a trailer to vehicle where the trailer lights flash? If so, then it’s more than likely your vehicle incorporates a CAN-bus system. ‘What the hell is that?’ I hear you ask. The concept is actually fairly simple and it certainly helps to have a better understanding of your vehicle’s electrical systems and how they interact.
CAN-bus, alias Controller Area Networks, is a system of communication primarily developed for motor vehicles. In a way, it’s not too dissimilar to optic fibre supplying internet to your home. Multiple signals are able to flow through the single ‘pipe’ at the same time. In the vehicle, multiple signals can flow to various accessories through the same cable system.
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CAN-bus was introduced into the automotive game to simplify vehicle wiring harnesses, eliminating mechanical relays and reducing vehicle weight, in turn leading to savings on fuel and money.
This new era in vehicle wiring and control simply means more sophisticated and reliable vehicles manufactured with less impact on the environment.
Electrical circuits which can be controlled by such methods include headlights, indicators, brake lights, air conditioning, ABS braking, reverse lights and sensors, even your electric mirrors and windows.
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A common scenario nowadays seems to occur when people are wiring up electric brake controllers for trailers. Crawling under the dash trying to locate that hard to And brake light trigger.
More often than not, it’s as simple as grabbing your test light and going straight for the brake light switch. Well be warned! With these new CAN-bus cables and modules, often referred to as ECMs (Electronic Control Modules), you need to take caution when delving within your vehicle’s electrical systems.
When the modern-day vehicle is fitted with a trailer plug at the rear, most have a type of CAN-bus converter fitted that can decipher these electrical CAN-bus signals and convert them into a DC (Direct Current) signal that will operate the incandescent or LED lights on the trailer.
When wiring up these trailer brake controllers, most are opting to take the signal from the brake light wire at the trailer plug.
If you’re already running the output wire from the trailer brake controller then there’s not too much extra effort required to run another wire at the same time then or is there?
Be warned though folks, some of these modern vehicles sense the loads put on the brake light wiring.
These types of systems detect a trailer is fitted through the brake light circuit and will do things like turn off reversing sensors, cameras and even adjust the way the vehicle braking is applied i.e. stability control and anti-sway systems.
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I recommend using a test light to test the brake light output at the trailer plug (obviously without a trailer connected) before carrying out any wiring.
Whilst illuminating the test light with the brakes applied, try operating other circuits like indicators, tail lights and even selecting reverse gear. If you notice no problems, then it’s normally a safe bet to pick up your brake light feed at the trailer plug.
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It’s always a good idea to consult REDARC before fitting accessories or controllers to make sure everything correlates. Take my advice on this one folks, if in any doubt or you’re not confident then leave it up to your dealer or an experienced auto electric specialist! www.redarc.com 4WD