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Dang 'ol pointy head avionics troops. As a former AGE technician, I can confidently say you're overthinking it.
LOL - you brought back some fond memories of what it was like
to be the geek that others would flee when we started talking about
our stuff.
Seriously, when someone first starts out in electrical troubleshooting
they really rely on what the meter tells them. But as they build experience,
they discover that by using their other senses at the same time allows
them to troubleshoot while using the meter less for actual troubleshooting
and more for just pre/post verification.
****
Here's a quick example. I was asked to troubleshoot the hard starting
of a '70 Chevelle with a high-compression 383ci SBC. It was a slow cranking
issue that had resisted repair by others. Battery had been upgraded
to a stout one with 800 cold cranking amps. Battery was fully charged,
and passed a load test easily.
Car would barely start cold, and when it was hot it wouldn't turn over
fast enough to start, so the owner would be forced to open the hood
and wait for the engine bay to cool before he could go home.
All relevant connections were clean & tight, and would have passed
any resistance check I might have made. The starter sounded healthy
& shimmed up correctly, just too slow. I knew that a lot of current
was being drawn, for if you watched the positive cable down to the
starter it would jump ever so slightly when the key was turned to
start. (!)
The problem? The best we could tell, that '70 Chevelle had a low
compression 307-2bbl when originally built. Both positive & negative
battery cables were original, in good condition, but were sized like
something you would expect to see on a straight 6?
I told the owner that we needed to upgrade the battery cables
to better match the requirements of the high compression
383. I recommended that whatever GM did for the LS5 454 equipped
'70 Chevelles would be the place to start.
That's what we did. He actually got the cables listed for the big block,
and they were indeed much heftier. And from the first start with the
new cables we knew we had a solid fix! Worked as advertised, hot or
cold.
And I didn't use a meter for any of this. After decades of intently
watching all manner of SBC & BBC engines start, you just see
the patterns & react at a near muscle memory level. And if I had
to guess, Erik I bet you worked in a similar fashion on your AGE.
We start out using our written guidance like a cookbook, step by
step, hoping like hell that we were being led to a successful resolution.
But after enough time in the kitchen, while the book may still be
open, my nose is now guiding me through the process. (Yup,
this stew now smells the same way that it did the last time, and that
was a crowd pleaser!)
****
Actually, my goal was not to try to get the OP to break the piggy
bank & fill a cabinet with specialized test equipment. Instead, I
just wanted him to know that if he was getting squirrelly readings,
it wasn't his fault so much as the limitations of all handheld multimeters.
And that it *is* possible to quantify very small amounts of circuit
resistance in milliohms reliably. (or large amounts of conductance in mhos,
take your pick.)
But with a little experience, if he chooses to, someday he will simply
stand by the front fender helping a friend or neighbor troubleshoot,
listen to the motor crank over, see the too-small cable, and know
that it isn't up to the job.
And the whole time there won't be a meter in sight. :0)