I would like to wire two six inch 100w lights to my high beam switch. My questions are: Is this even a good idea? Do I need to add a relay and what does a relay do? Will the switch handle the extra load?
You should definitely use a relay. Two 100W lights will draw about 17 amps. I doubt that the high/low switch is rated for that much current. The coil in the relay should draw about 1/2 an amp. You can probably use the high/low switch to energize the relay without adverse effect. Check you service manual because I'm just spouting electronic theory here.
I recommend putting a separate switch. Then you'll be able to use the lights with your low beams at night in traffic. Just fuse it and run it to the battery, it's the same amount of work as adding a relay which you'd otherwise definitely be wise to install.
The reasoning for using the existing hi beam switch is the lack of finding a suitable handle bar mounted, water proof one. If I used a relay for each light would that work? Thanks for the replies.
If you can't find a switch to your liking, consider an Autoswitch. http://www.autoswitch.com/2006/models/as5p/as5p_index.shtml This will allow you to use your existing switchgear and still differentiate functions between high beams and auxiliary lights. I use one of these to turn on the PIAAs on my R1150GS hack and it works very nicely. However, you will still need to employ a relay.
After doing a little searching on the www I found this cool diagram. It helped me understand how to wire a relay. So easy, I can do it
And this is what a relay looks like: Just trying to help some one else out. I'm sure I'm not the only moron that didn't know this dark art of wiring an aux. light properly
