Sounds like you had a mechanical temp gauge not electric. You just cut the conduit that carries temp sensing medium which pushes on the diaphragm...
Either hit it with PB Blaster, but probably will need the blue wrench. Or if you can cut the sleeve in half, you may be able to pry and then...
Don't forget the grill and lites, people in my club are buying them as wall hangers in the man cave..,
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