Regarding the "flying short", the root of most electrical problems that have
no logical reason for happening would most likely be traced back to
connectors. These cars were never intended to last 30 years. Connectors
corrode and become resistors. Resistors get hot because they impede current
flow. Abrasion inside the connector while driving can wear corrosion and
"fix" the connection temporarily.
If you take a new car to a dealership with a fuse blowing problem, chances are
the mechanic will put a nail in the fuse position and see what blows. I don't
recommend this in a car as old as ours. Constant shorts are much easier to
find. You start from one end and work to the other (power, instrument).
Intermittent shorts change the rules on you.
Original wiring harnesses use copper conductors (wire) bare copper or plating
over copper terminals. Copper oxidizes rapidly when exposed. This oxidation
breaks down the material (copper) much like rust. The wire becomes brittle
and can break over time through oxidation and vibration. An intermittent
short will become a permanent short given time.
In other words, always suspect the connector first, check the wiring second.
Just my 2c
Dave Ford
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