After following the recommendation of sanmiam, I realized that instead of trying to educate the principles of gauge operation it might be simpler just to do a quick fix instead of trying to run down many problems that could effect the gauge.
Running an external regulator isn't a new idea, jeeps have run an external regulator decades before the introduction of the AMC era CJ's.
The regulator sanmian recommended was a nice little waterproof design with mounting tabs and efficient 12 volt to 5 volt buck boost circuit. (Don't worry about how it works.) Other regulators require a heat sink to dissipate the heat from reducing voltage. This doesn't need one.
I purchased one from Amazon for $8.59 with free shipping if you have prime.
I put a 12-10AWG Bullet connector on the RED power in lead to easily plug it into the RED power lead in the jeep harness.
You cab cut the black wire next to the RED wire as it's the same ground on the output side and I think it makes for a neater installation
I connected the Yellow wire onto the "A" terminal and the BLACK wire onto the ground point on the speedo housing. It really can be grounded anywhere as the speedometer no longer needs to have a good ground. (Except for the speedo illumination and turn signal and High beam lights. OK so ground it. )
I used one of the screws that attach the speedometer to the housing to mount the regulator
And that is all there is to do to hook it up.
NOTE: This doesn't fix everything. You still could have shorted wiring, bad sensors or broken wires in the gauge.
A simple test by disconnecting the sensor wire and testing with an Ohmmeter between the "S" terminal and "A" Terminal and if you get a reading around 20 ohms (+/- 5 ohms) this ghetto fix should work.
Onto the testing.
I hooked my test box up to the gauges and tested the Low band, half band and full position with the regulator and the OEM regulator.
5 Volt Regulator:
5 Volt Regulator:
5 Volt regulator
Any small differences can be corrected with calibration if the gauges are OEM or Crown. Omix gauges are not adjustable.
Easy to hook up
Not much adjustment to read correctly if any.
No additions needed to the existing harness
No heat or exposed connections to short out.
Slower response time
Environmental conditions could effect accuracy. OEM automatically adjust for extreme temp ranges.
A 'Tip of the hat" to sanmiam for finding this regulator.
Let's give it a name.
Will post temperature extremes tests.