[n86121]

As I recall, one half of the master switch is a sense line to the bus, as well as each regulator switch provides regulator voltage sense.

Under no load their resistance will eppar to be "0" (or damn close), but under any load the resistance is actually more. Just old contact surfaces.

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The most extreme example of this I have experienced was when I used regular automotive battery cables on my boat. A wire is just a wire, right?

A few years later at start of one season, the starter wouldn't turn. I measured cable resistance, which was zero. I measured voltage at battery and going IN to starter, of course was 12... something. But somehow, magically, when hitting starter, the starter end would drop down to ~6 volts. The battery cable had corroded INSIDE the insulation somewhere, and when hit with 300 AMPS became a big resistor.

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Similarly, when those switch resistance increases under load (1-2 Amps I think), even 0.1 ohm can throw the sense voltages off, and the remote regulators and alternator control signals start chasing ghosts.

I recall seeing upwards of a volt across the 'closed' switches.

Being more lazy than cheap, I partially lifted the switches out, to expose their guts, then used contact cleaner squirted above and below and into the switches, and cycled the switches a LOT of times to 'wipe' their internal contact surfaces.

The 'closed' (under load) voltage across the switch contacts dropped down from around 1 volt to some teeny tiny fraction of a volt, "and all was well in the land,"