CO2 showing almost empty

I kegged a beer on Saturday and my CO2 tank was reading in the green area on the gauge.  I checked all connections with Star San from a spray bottle and no leaks.  My pressure was set at 11 psi for the newly kegged beer and 1 other connected to the CO2 but that was fully carbonated before.

Last night I check the tank and the gauge is in the red zone stating it is almost empty.  I checked again for leaks and didn’t find any.  I turned the pressure up a little and can still hear gas flowing, then turned it back down to 11 psi.  My tank sits in my kegerator with the kegs at 40F.

Do the gauges read incorrectly if they are in the kegerator because of the cold?  I can’t believe this tank went from green to red in 4 days when I can’t find a leak.

Also, is there a good way to tell if a tank is empty?  It is a 5lb, aluminum tank.

Thanks.

The gauge will read less when the tank is cold.  Set it in a room temp place and it will go up.

To check if it has CO2, the tare weight should be on the tank, so weigh it without the gages.  The weight-tare=CO2 weight.

+1
The only way to tell how much CO2 is there is to weigh the tank and subtract the tare weight.