[Steve '93ES]

This is on the Diamante?
I'm sure you know there are two sensors (on the 3S anyway). one smaller switch for the light and a larger, mushroom shaped sender for the gauge.
I'm not sure the wiring is the same, but on the 3S taking the wire off the smaller switch and grounding it (with key on) should turn the light on.
If it DOES light up then the bulb, wiring, and fuse are OK. Try plugging the wire back on to make sure it wasn't just loose. (You might get under there and find it just popped off! ) If that doesn't fix it then the switch is probably bad.
If it DOESN'T light when you ground the wire (remember, the key has to on) than it's likely either the bulb or the fuse.
The "Brake" light is on the same fuse so a quick pull on the parking brake can tell you if it's the fuse...

 

[Steve '93ES]

Hopefully solved... Let us know how it turns out!

 

[Steve '93ES]

I wish all the fixes on these cars were $6 and 20 minites or less. 😞