Topic: Help diagnosing short

[OneWheelDrive]

1975 CB550, with the off/on switch on right control, high/low on left, stock wiring except dummy lights and speedo lights replaced with led. When I turn the lights off from the right control, I'm getting a short I can't track down. Why would it be shorting when I'm turning the lights off??

[CB650CPastor]

How do you know you're getting a short? Does the fuse blow?

[OneWheelDrive]

Yes, blowing the lighting fuse

[Don R]

   I'd have a look inside the right control first.

[CB650CPastor]

Yep. Check that control. If it's fine when the lights are on but blowing the fuse immediately when you turn them off, I'd be checking that switch. It may be grounding the positive terminal when you switch it off. If the lights actually work without blowing the fuse, that pretty much rules out the wiring (if it is all connected correctly) and points to the switch.

[Frostyboy]

I'm curious now. If you turn the ign on with the lights off, does the fuse blow? Or is it only when you slide the switch from on to off?
To save you blowing countless fuses, remember that if you install a reasonably high wattage bulb across the fuse terminals it will save you changing them all the time. Use at least a 21 watt bulb. If the bulb burns brightly it's saying there's a short. That might let you track it down a bit easier. As you work your way through & the bulb goes out you've found the source.

[OneWheelDrive]

Got an update for y'all.  I opened the right hand control and all looked good.  Then I noticed that the rear light and brake light weren't working, so looked into what could be causing that.  Turned out the Lucas rear light wasn't properly finding ground on my freshly repainted rear fender.  I wired a proper harness ground and fixed it.  Not sure why that would be causing a fuse to blow when the lights were off, but the problem seems to be solved!

[Frostyboy]

So it's true! Joseph Lucas is the Prince Of Darkness. Good to know you got it sorted.