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Car Trailer lights issues

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Trailer lights issues
Not so long ago when the automotive industry used incandescent globes, it was a very simple task to hook your trailer up to your car right.

What about now ?

Sorry I need to tell you tell with more electronic additions, there are other factors that need to be considered.

Two major differences now may prevent the old trailer lights from operating on your new trailer.

The two major differences are LED lighting and CAN bus.

A Controller Area Network (CAN bus) is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other in applications without a host computer. It is a message-based protocol, designed originally for multiplex electrical wiring within automobiles to save on copper, but is also used in many other contexts.

Our very clever automotive engineers are wonderful at coming out with new features, perhaps they should ask me before they spend so much money in R&D.

Ok here is where the problem has been created.

A normal car without CAN bus and LED lighting will allow you to connect your vehicle to your normal trailer because we use incandescent globes.

We can also move into the 21st century and retrofit our trailer with LED provided we follow the simple rule of added the correct value resistor to pull down the load.

Now here is the smart system
Your new car may be that smart it can tell you if your brake light is not operating.
This was a breakthrough at the time to enhance safety, so it had my tick of approval.

Then someone had to come along and stuff it all up, yep the clever engineering team, also known as the smart engineers.

Now the indicator, brake and light circuit under the control of CAN bus, becomes complicated but simple at the same time.

A normal circuit will supply a voltage of 12 volts in a 12 volt system, so your old car is a 12 volt system.
Now your new smart CAN bus car is still 12 volts, BUT with some software and coding behind the circuit.

This is where the problem starts.
The supply to the plug maybe variable, this means that instead of having 12 volts for stop lights, lighting, and indicators you may only have 6 to 12 volts and this is variable.

If this does not make sense you are the normal one.

The dealership may provide a interface connector or trailer adapter to equalise the variable voltage supply.

The other way is to add a relay at the rear of the vehicle and convert the supply to signal, this way you will get a constant.

Send me an email if you need more clarity

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