Auxiliary lights get most of the attention when riders plan a lighting upgrade. Lumens, beam pattern, mounting position. The controller usually comes last.

That order is backwards. The light decides what you can see. The controller decides how you use the light: how you switch it on, how you dim it, and whether it reacts to your high beam, horn or turn signals. On a long night ride, the controller is the part you actually touch.

Today there are two main ways to control a set of motorcycle auxiliary lights. A CAN bus controller plugs into the bike's data network and lets you use the factory switches. A universal handlebar controller wires into the bike's power and adds its own switch. This guide explains how each works, who each suits, and how the two Q5 Pro controllers from RiderNav fit into the picture.

Why auxiliary lights need a controller at all

A pair of high-output LED lights is not a plug-in accessory. It draws real current, needs a stable power feed, and needs some way to be switched and dimmed. On most quality lighting systems, the dimming and protection logic lives in a separate controller, not in the light housing.

The Q5 Pro works this way. The light units contain the LEDs and optics. Power, dimming, colour switching and thermal management are handled by one of two controllers: the RLC3 universal controller or the RLC CAN-X BMW controller. Neither the lights nor the controllers work alone.

So the real question is not "do I need a controller?" It is "which type of controller matches my bike and my riding?"

What a CAN bus controller does

CAN (Controller Area Network) is the data network inside modern vehicles. It was developed by Bosch and is now standardised as ISO 11898. On a motorcycle, the CAN bus carries messages between the ECU, instrument cluster, switchgear and lighting. When you press the high beam switch or roll the thumb wheel on a BMW, that action becomes a message on the bus.

A CAN bus controller listens to those messages. It reads the state of the high beam, turn signals, hazard lights, horn and, on supported bikes, the factory multi-function wheel. It then drives the auxiliary lights to match. Some CAN controllers, such as Denali's CANsmart, are configured through desktop software, with each output circuit assigned a function on a computer. Others ship with fixed, pre-programmed behaviour and need no software.

The practical results are the same in both cases:

• No added switch. The bike's existing controls run the lights.
• Plug-in installation. The controller connects to a factory CAN connector through a model-specific adapter. There is no splicing into the loom.
• Bike-aware behaviour. Because the controller knows what the bike is doing, functions like turn signal sync and hazard sync become possible.

The trade-off is scope. A CAN controller only works on bikes whose CAN messages it understands. That is why these controllers are sold by model or model family, and why the adapter cable has to match the connector on your specific bike.

What a universal handlebar controller does

A universal controller takes a different route. It does not read the bike's data network. It connects to the bike's electrical system directly: a power feed from the battery, an ignition-switched (ACC) trigger, and optional signal leads for functions like high beam sync or horn-triggered flash.

Control comes from a dedicated switch mounted on the handlebar, usually a knob or a button cluster. The rider presses to power on, turns to dim, and holds or presses a combination for flash or colour functions.

The strengths of this approach:

• Any 12V motorcycle. The controller does not care what brand or year the bike is, or whether it has a CAN bus at all.
• Direct, tactile control. A physical dial gives fine dimming and does not depend on how the factory switchgear was designed.
• Independence from bike electronics. The lights are electrically separate from the factory lighting logic, which some riders prefer.

The trade-off is installation effort. You need to run wires, find a suitable ACC circuit, and mount the switch. On the RLC3, RiderNav quotes 60 to 120 minutes for riders who are comfortable with basic motorcycle electrical work, or under an hour at a shop with auxiliary lighting experience.

CAN bus vs universal: the key differences

Neither column is simply better. They optimise for different things: integration on one side, universality on the other.

Who should choose a CAN bus controller

A CAN bus controller makes the most sense if all three of the following apply:

1. Your bike is on the supported list. This is non-negotiable. The controller and its adapter cable have to match your model and, in some cases, your model year.
2. You value a clean cockpit. If you already run a navigation display, a phone mount and heated grip controls, one more switch on the bar is a real cost.
3. You want the lights to behave like factory equipment. Turn signal sync and hazard sync only work when the controller can read those signals from the bus.

The typical buyer is a rider on a current BMW GS, RT, K 1600 or similar model who does long tours and wants the auxiliary lights to feel like an original option rather than an add-on.

Who should choose a universal handlebar controller

A universal controller is the right call if any of the following is true:

1. Your bike is not supported by a CAN controller. This covers most KTM, Honda, Yamaha, Triumph, Ducati and Kawasaki models, as well as older or carburetted bikes.
2. You want fine, direct control of brightness. A stepless dial lets you set output exactly where you want it, rather than choosing between fixed levels.
3. You plan to move the lights between bikes. A universal system transfers to the next bike with no compatibility check.
4. You prefer the lights to stay independent of the bike's electronics. Some riders simply want a lighting circuit they fully understand and can troubleshoot with a multimeter.

The typical buyer here rides a mid-weight adventure, sport-touring or naked bike, does regular night commuting or weekend trips, and is comfortable with, or willing to pay for, basic wiring work.

How the Q5 Pro controllers fit

The Q5 Pro is sold as a system: the light units plus your choice of controller. RiderNav offers one controller of each type, so the choice above maps directly to a product.

RLC CAN-X: the CAN bus option for BMW

The RLC CAN-X connects to the bike's factory CAN bus through a model-specific adapter cable. It ships pre-programmed with six functions and needs no software configuration:

• High beam sync — the Q5 Pro lights come on with the high beam.
• Turn signal sync — the lights flash with the indicators.
• Hazard light sync — the lights flash with the hazard switch.
• Horn-triggered flash — a rapid audio-visual alert that fires the spotlights in sync with the bike's horn. The signal comes from the CAN bus, so no extra wiring is needed.
• Cruise Strobe — a sustained attention-grabbing flash mode. Press the flash-to-pass button five times within five seconds to activate it, and press once to exit.
• Four-level brightness with memory — the controller stores the last on/off state and brightness level, so the lights return to the previous setting at the next start.

Everyday control runs through the factory Multi-Controller (the Wonder Wheel). On first activation, the lights are powered on with the turn signal stalk, then a long press of the Wonder Wheel to the right brings the Q5 Pro into the wheel's control loop. From there, brightness is adjusted in four preset levels. Four levels is a deliberate choice: it matches how every other adjustment on the bike behaves, so the spotlights feel like a factory-integrated feature rather than an aftermarket add-on. Three adapter cable variants cover the supported models:

Before ordering, confirm the exact model and model year. If your bike is not listed, the RLC3 below is the correct alternative.

RLC3: the universal option for every other bike

The RLC3 is a rotary dimmer controller for any 12V motorcycle. Its handlebar unit combines an encoder dial and a dedicated auxiliary high beam button, and it controls the lights through four inputs: power, ACC, and optional high beam and horn sync leads.

What it does:

• One-press power on and off.
• Stepless dimming by rotating the dial, with no fixed steps.
• Colour-shift indicator — the dial's backlight moves from green at low output to blue at full output, so brightness can be read at a glance.
• Dual-colour switching between the white driving beam and the yellow daytime running light mode.
• Warning flash, plus high beam sync and horn-triggered flash when the optional leads are connected.
• Memory of the last setting at the next start.

The harness is segmented and colour-coded, and the two sync leads can be connected or left off depending on how you want the system to behave.

What both controllers share

Both controllers run the same Q5 Pro light units and the same thermal management, so the beam, colour and output are identical whichever you choose. Both include memory of the last state. The differences are the ones that should drive your decision: how the controller connects, what it can read from the bike, and how you adjust brightness.

A quick decision checklist

• Is your bike on the RLC CAN-X list? No → RLC3. Yes → continue.
• Do you want to keep the handlebar free of added switches? Yes → RLC CAN-X.
• Do you want turn signal and hazard sync? Yes → RLC CAN-X.
• Do you want stepless dimming from a physical dial? Yes → RLC3.
• Might you move the lights to a non-BMW bike later? Yes → RLC3.

For mounting options, beam patterns and installation guides, see the RiderNav lighting guides.

RiderNav is not affiliated with BMW Motorrad. BMW is a trademark of BMW AG.