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R1100RT wiring for aux lights


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I'm installing some Wally World aux lights and am struggling with how to wire these. 1st thought is wire directly to the battery with an on-off switch under the seat. That way they are always on, have a dedicated circuit and no overloaded wires. But I'd have to remove the seat both before starting and after starting. Where is a switched power lead near the battery on the R1100RT? Colors and gauge to identify would be helpful.

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Danny caddyshack Noonan

There are several options. Switch the relay from the headlamp low or high beam and provided the lamp power from the battery or, a 10ga wire coming off of the battery to a bus bar or something that allows for later expansion for other things.


You can also switch the relay with the positive side of the switch connected to most any of the hot leads in the dash. Use a voltmeter or DMM to find one. They're there. Then power the lights per the above.


Another might be to use the blue alternator wire to provide the supply side to the relay (optional to put a switch in series with it). The blue wire will let you start the engine without drawing down power. The alternator doesn't put power out until about 2000 rpm. I have a lot of my accessories driven off of a relay hooked up to that wire. It is fairly failsafe since the relay goes open circuit when the engine is shut off but stays closed circuit at idle, once it gets closed just after starting. Power the lights per the above.

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There's not a lot of real estate on the dash. Any suggestions on an easy to reach place for the rocker switch. Pics would be really appreciated. My R1100RT has NO farkles and nothing to attach to for the 2nd accessory.

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do it right use a relay and a fuse

here is a schematic to wire it with




here is neat switch to control the light it has double sided

tape on the back and will stick on the dash and it has a built in





this guy carries a lot of parts also




the relay I use is a standard one (bosch type) that is used

on fog lights and usually can get in any auto parts house.




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Whatever you do do NOT connect lights directly to to an existing circuit - not even the lighting circuit. The wiring on BMWs is too thin, marginal at best for the load attached at the factory. Putting a pair of lights onto an existing circuit is very likely to burn out you loom and they are VERY expensive to replace.


Take power from the battery via a relay. Trigger this relay from a switched source, add-a-circuit is a neat way to do this. Fuse #2 is probably the best source for the trigger - it is for the parking and tail light and is on the load-relief circuit, so will switch the lights off when the starter is pressed.


There is plenty of room under the seat for a relay - but I would use one with a bolt-mounting tag on it an put it up under the dash to be sure the wiring cannot short to the bike frame.


A picture of the fusebox:




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Use a relay to power the lamps. Take power from the battery and trigger the relay off of the parking lamp wiring. That circuit is on the load shed relay, so the Aux Lights will shut off when you hit the starter button. I left the on/off switch in the relay wiring and just buried it under the seat in the ON position.

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I put in a FuzeBlock. It has a constant and a switched powered side. Then ran the light circuit directly from that to the lights.


Works well, is fused, and the relay is embedded in the FuzeBlock.


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I've used an autoswitch for a while now and it's been trouble free and very convenient. It is triggered by the turn signal cancel button, so there are no new swithes on the bike. It sort of flashes the turn signals when I trigger it, but that may be because I also have a signal minder on the circuit. But anyway, that isn't a big deal. It was pretty easy to install.




The rest of the install is as above with a relay for the lights.


mike g


99 R1100RT

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