I had the same issue yesterday when I filled up my 2007 CV LX. The gauge showed empty and the computer also said I was empty even with 16 gallons in the tank.
Here is what I did to fix the problem:
1) Shut off the car, leave in park with the keys out of the ignition.
2) Disconnect the battery. I un-did both the positive and negative terminals.
3) Let the car sit with the battery disconnected for 5 minutes or so.
4) Reconnect the battery.
5) Turn the car back on and it should work again.
I don't have an answer as to why the gauge stopped working but it also happened at the same time my oil light reminder came on due to low oil life (5%).
Hope this helps. Definitely worth a shot instead of going to a mechanic and paying $$ for possibly a simple fix.
On a 1996 Ford Crown Victoria : The H / L ( High / Low ) gauge : On the drivers side of the speedometer is the battery voltage gauge On the passenger side of the speedometer is the engine oil pressure gauge
I was looking at the drawings of the instrument panel ( gauge cluster ) in the 1997 Ford Crown Victoria Owner Guide and it doesn't have a factory tachometer
Cause it doesn't have one
Voltage regulator is defective. Have it replaced or this will ruin your battery.
If you don't have a temp. light, or temp gauge, then just install one.
Bad gauge Bad float in tank
it might be a fuse
no power at the sending unit.
Float could be stuck in the tank or the ground wire on the tank is broke.
It is in the fuse box underneath the dash. Do you have tail lights? If not, you may have a bad light switch.
Depends on the car. Most should drop to empty when the ignition is off but some cars stay in the same position, they are rare though. (Toyota crown, Isuzu panther)
Either the sensor is broken or Your gaug on the dash is not working.