What is this?

see white arrow in pic., looks like a condenser. what is it? Voltage limiter?

these are guage clusters out of late 66 fury's
the gauge cluster on the left if out of my 66 Monaco(canadian version) it never had that cylinder thing mounted to it.
the gauge cluster on the right is a spare that my father(original owner of the car) picked up years ago. not sure what year car it came out of.

the only difference between them is the cylinder thing mounted as shown, and is connected to the +12V input terminal of the fuel gauge.

thanks
Glen
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Author: Labradorian