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Brake Light Relay to Prevent Motorhome Turn Signals Being Overridden By Brake Lamp on Towed Vehicle


I am adding the Hopkins tail light Isolating diode system #38955 on my 2005 Pontiac G6 and will be using a Brake Buddy supplemental brake system. When the Brake Buddy applies the brakes, the brake lights on the car are illuminated and at the same time the motor home lights will also illuminate the brake lights. Will this harm either the diodes or the brake lights? Would it be best to remove the fuse for the brake lights while towing?


Expert Reply:

You'll need to install a Roadmaster Brake Light Relay, part # RM-88400. The purpose of a brake light relay kit is to prevent your towed car's brake signal from overriding the turn signal that comes from your RV. When your towed vehicle is properly wired and connected to your RV, its indicator lights will illuminate as you engage the turn signals in your RV. However, if you have only a four-diode system in place, the turn signal will be overridden by your towed car's brake signal as soon as your supplemental braking system presses the towed car's brake pedal. As a result, drivers behind you know only that you're slowing down and not that you are turning. It's not going to harm anything on the vehicle, but the taillights won't be working properly.

Installing a brake light relay in your towed vehicle fixes this problem by ensuring that your car's brake signal does not override the RV's turn signal. Therefore, your towed car's lights will function in accordance with your RV at all times.

The bottom of the product description page has a diagram showing how the relay would install.

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expert reply by:
Mike L

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