If you’re installing a supplemental braking system, chances are you’ll need a Brake-Lite Relay. It must be installed in the majority of towed vehicles to enable the towed vehicle’s brake lights and turn signals to illuminate in tandem with the motorhome’s, as required by law. Brake-Lite Relay stops the brake lights from functioning until the vehicle is started. This prevents the towed vehicle’s brake signal from overriding the motorhome’s turn signal. When you tow without the Brake-Lite Relay, your towed vehicle’s brake lights alone will work fine. Your turn signals alone will work fine. But if you’re braking and turning, the brake light from the towed vehicle will override the turn signal from the motorhome and drivers behind you will be unaware you’re about to turn.