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Wiring a relay into the brake light


BeemerEric

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I was looking into doing my own brake light upgrade using Whelen LED lights. My idea was to tap into the brake light and use the power from that to run a relay to switch on the Whelen LEDs. I found a relay that draws only 35 ma, does anyone know if that amount of current will cause a fault in the can-bus system?

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I was looking into doing my own brake light upgrade using Whelen LED lights. My idea was to tap into the brake light and use the power from that to run a relay to switch on the Whelen LEDs. I found a relay that draws only 35 ma, does anyone know if that amount of current will cause a fault in the can-bus system?
I suspect you will be fine. Go ahead and try it. Worst case if the system then shows a brake light failure, all you'll have to do is take it back out. No harm will be done.
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Ken, I did it without any problems. I installed a set of Hyper Lites on my ST. The kit requires a connection to the brake light. I also have my fused-relayed accessory harness wired to the brake light (powers GPS/XM/V1). To make troubleshooting/future upgrades easier I ran a wire from the bulb connection to the under-seat area. I connected the other leads to that cable.

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I was looking into doing my own brake light upgrade using Whelen LED lights. My idea was to tap into the brake light and use the power from that to run a relay to switch on the Whelen LEDs. I found a relay that draws only 35 ma, does anyone know if that amount of current will cause a fault in the can-bus system?

 

I know of 3 1200RT's that have the 16 bulb Hyper-Lites installed, including mine, and no problems....Tapped into the brake light....

 

Phil..........Redbrick

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So, Tony,

 

The GPS, XM & V1 only come on when you hit the brakes?? blush.gif

 

Carl

LOL! Hee-hee, some how I suspect he meant the tail light!
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I was looking into doing my own brake light upgrade using Whelen LED lights. My idea was to tap into the brake light and use the power from that to run a relay to switch on the Whelen LEDs. I found a relay that draws only 35 ma, does anyone know if that amount of current will cause a fault in the can-bus system?

 

I know of 3 1200RT's that have the 16 bulb Hyper-Lites installed, including mine, and no problems....Tapped into the brake light....

 

Similarly, I tapped the brake light on my 12GS to light the stoplights in my Givi topcase (2 arrays of 6 small incandescents). No relay is involved. That was several months and several thousand miles ago, with no problems experienced, and nothing mentioned to me when the bike was serviced by the dealer and by an independent BMW Master Certified tech.

 

YMMV.

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Yes I did mean TAIL light.....

I'll shut up now..............

 

So, Tony,

 

The GPS, XM & V1 only come on when you hit the brakes?? blush.gif

 

Carl

LOL! Hee-hee, some how I suspect he meant the tail light!
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I'll shut up now..............
FWIW, I for one wish you wouldn't - your install is one of my favorite ST electrics installs I've seen/read about... thumbsup.gifthumbsup.gifthumbsup.gif

 

Of course, we all aspire to be Ken H when we grow up - don't we? smile.gif

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I was looking into doing my own brake light upgrade using Whelen LED lights. My idea was to tap into the brake light and use the power from that to run a relay to switch on the Whelen LEDs. I found a relay that draws only 35 ma, does anyone know if that amount of current will cause a fault in the can-bus system?

If this is in addition to the current normally drawn by the tail light, then it will work perfectly. Be sure the contacts are rated for the current drawn by the LEDs. One nice thing is that because the LEDs are purely a resistive load, no de-rating is required (filament lamps have a huge inrush current, requiring larger contacts to handle it; LEDs do not).

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