oil temp gauges

[stevo]

i have these four oil temp gauges, all 2.25".
1]vdo: measures to 300*; light bulb socket, and three contact posts [2 at top, 1 bottom]
2]westach: measures to 250*; no light bulb, three contact posts [one top, 1 bottom, 1 bottom left] and 2 thin blue wires coming out of bottom right. one of the blues is hitched to the bottom right post, the other hangs free.
3]störk: measures to 250*light bulb socket; one thin copper wire cased in black - cut at about 2 feet.
4]sw: i bought a bus with a siezed engine. it has an oil gauge that is spiked at 300*. is that something or what?

kinda different huh? here are my questions. why just one black wire coming out of the third gauge? which one is best quality?
_________________
When you cross an Irishman, they never forget. I mean, never.

[OMT]

That cut off wire on the "Stork" gauge goes to a dip stick or a bolt on sender. It used to be filled with ether? or some other gas or liquid. It's not electric; it's a "mechanical" connection. What is best....I don't know.
Later,
Al

[stevo]

[OMT]

Yea, it can be fixed. It ain't cheap. I went to North Hollywood Speedo. Palo Alto speedo can also fix it.
Al