Originally Posted by nakman
Dave back on the relay thing... I haven't been around since 1962 so am a little slow perhaps. Is the benefit of the second relay so I don't need to run 35w through the switch?
It's an either/or between 87 and 87a, correct? Power to 85 flips it between those.. so my handlebar switch high beam wire is going to trip #85, and I just wouldn't hook up the low beam, is that what you're saying? Resulting in default low beam, switched hi beam. But both are off with relay #1 being switched off. Ok I think I get it now..
Yes. You have a kill switch and the second relay (e.g. #1 in the description) is there so that you do not switch high current directly.
You have it right, what's on terminal 30 goes to 87 or
87A depending on the state of the coil. So you have a high beam switch that when off gives you low beam and when on selects high beam. It toggles between the two.
Remember relays are electroMECHANICAL devices, so they do things mechanically that are reactions to electrical changes. Energize the coil and you overcome a spring, which reacts oppositely when you de-energize the coil.
I can add that if you wanted, it would not be difficult to wire this so that you can use a momentary switch (e.g. push to switch to high, push again to switch back to low) that also resets to low beam when the power is removed.