Posted by: @5556

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I changed out the battery in my "72 SWB 75/5. Hooked the cables back up and the high beam came on. Ignition was off. I had pulled the tank, so looked for pinched wiring along the frame, but all looks kosher. I had moved the subframe back about a 1/2-inch, but don't think that disturbed anything either.

I'm thinking maybe it was just a coincidental failure of something like the ignition switch/nail thingy. Pulled the head lamp. I have a wiring diagram, but I'm not very smart. 

Or, better question, what might I have done to my bike to cause this? And what/how do I take the next step in diagnosing this?

* That is indeed strange. Are you sure the "nail" hasn't simply been removed in the headlamp ON position ?

* Your issue has to be somewhere within the headlamp-mounted ignition/HL switch, the wires going up to the bar switch, or within the bar switch itself. You almost certainly have a mechanical or water connection between the RED terminal and those that power the headlamp circuit. Inside the "nail switch" is the most likely location because the RED and HL wiring are both present there.

* Any RED wire is directly connected to the battery. No fuse. No cutoff switch. IOW, it's always powered ON.

Posted by: @5556

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On the ignition switch, I checked for continuity between the red wire terminal (source of 12 V, I figured) and the brown wire terminal (ground) with the key out. I got continuity. Should that happen? Seems like everything in there should be disconnected with the key out.

Red goes directly to the Pos battery terminal, and Brown goes directly to the Neg battery terminal. I believe you are simply reading the /5's battery voltage. You should always get 12 volts between those 2 terminals (Power & Ground). Your continuity tester is nothing but a voltmeter and is probably powered by an internal 9V battery. 

I think you should put the continuity tester down. It's the wrong tool for this job and a big motorcycle battery won't have any trouble frying the tiny circuitry designed for a 9V battery.

Get yourself a "mechanic's test lamp" like this...

Thanks. I suspected I might just be reading 12 V on the battery and this confirms it.

I have several test lamps and will use one.

I have never had a 12V vehicle battery "fry" a multimeter, but I guess it could happen in the future.

The continuity or resistance portion of most multimeters can be fried by line voltage.  The small battery in the unit is the only power source for most modern units.  

Continuity checking and resistance checking is done ONLY on powered down and carefully isolated circuits.  

Continuity and resistance checking are a different function of troubleshooting and have particular methods which must be followed in order to get proper readings and to prevent damage to the test unit. 

The voltage and amperage functions on the multimeter are not bothered by this problem, LOL, as long as they have a rating high enough to read the voltage or amperage.  

Yeah I am sorry I don't mean to be a wise guy.  St.

I believe the problem is in the multi-switch. Had nothing to do with my replacing the battery. Ordered a new one from EME.