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Some people here have taken them apart, but I have not.
FYI The very center of the back is the ground contact.
You can test for resistance but if you can see one of the wire coils is burned up, then that's not a good sign. A little evidence of heating wouldn't worry me if it resistance was OK.
I test mine three ways.,
First was a resistance test. Then checked and found resistance in the board. Posted here
Gauge Cluster Issues/IVR
Then attached a couple batteries to power, and finally used resitors to simulate sending units and test the whpole kit and kaboodle on the bench.
But to your specific situation. Go through this thread for and you'll see the gages should be 20 ohms, andthe IVR should be 50 ohms. if they don't pass that there's no reason to go further.
[URL]https://www.forabodiesonly.com/mopar/threads/bench-testing-rally-gauges.455180/[/URL]
The Chrysler Master Tech book and film explain how they work.
[URL]http://www.imperialclub.com/Repair/Lit/Master/227/index.htm[/URL]