Hi Mr Leo! FWIW a > 10% voltage drop across a switch sounds too high to me. Depending on current it's liable to get hot, I think. You may have more than one problem though, and that's always a braintwister. I wonder, if a high resistance in the feed to the switch might be dropping the switch input voltage under load, and the switch itself might be ok... Just my speculations...you're there, not me. I have had wiring that had partially broken strands inside the insulation, rarely. I'd WAG guess that a motorcycle wiring harness would be designed for < 2% loss in steadystate run... Best o' Luck! Keep us with the troubleshoot.
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Flaring off excess fuel>
To-day on the old XS gal, which is a bit like Johnny Cash's Caddy, bits from various years, nominally an '81... Well, the recent heat shields that I fitted on the shorties to prevent the heartbreak of burning boot syndrome, worked. Took the lady up to 95 or so on "my" back road. It's about a 15 miles loop of two lane blacktop...about 6 of which is copfreezone, usually! (the one time I met a cop out there my beanie was on my knee - he waved and went on.)
Like the old hot oil VW dipstick check, if you can keep hold of a thing it's not too hot. I was able to keep a palm on the outer side both left and right. Just. The kicker just clears the right side shield. They're stainless. Sneakers did not melt.
Upon return, I took the Sporty out and ran the other way 'round. The creeks are running full and fast, what with the bigbigsnowpack all melting. Cows and horses... Very "pastoral" and pretty.
When a rich uncle drops off his twig I'll buy a magic electro-camera and make some flicks of the local roads.
Best! 40N