New kegger -- proper full co2 tank read?

Hi all,
I'm new to kegging and just bought me first CO2 tank this past Friday. I bought the tank, had it filled and put it on my freshly kegged irish ale on Saturday. When I hooked it up, I noticed that the high pressure side of the regulator is measuring somewhere between 1,000 and 500 (i.e. get more gas). It's a 5lb tank.

I was thinking the gauge on a full tank would read more around 3,000. The tank and the reg. are in a 38 degree fridge, and I know that the temp has an effect on the CO2 and the reg, but should it register that low or did I get a short fill? By the way, I did the spray with soap solution to check for leaks and have none as far as I can tell.
Thanks.

Not sure what you mean, but with the tank hooked up to a keg you can turn the screw and the gage readings will change.

Mine is about 600 psi when sitting inside of the fridge. Don't worry about it until the gauge says zero.

You can't trust the gauges when the tank is in the fridge, they never work right. you'll have to take it out and let it warm up if you want to see how much gas you got.

You need to weigh it and subtract the tare to know how full it is.

Like Rob said above, the only way to know how much CO2 is in your tank is to weigh it and subtract the weight of the tank.

There is a direct pressure/temperature relationship with compressed CO2. The pressure will stay exactly the same , at a given temperature, until all of the liquid has been vaporized. Once only vapor exists the pressure will drop rapidly. Here is a pressure/temperature chart for CO2 that shows that relationship.

Thanks for all the advice!

Regardless of where you keep your tank, once you hit 300 psi, you are on vapors and need to refill.

3000 psi is where the safety valve pops. I'll told that it is exciting when this happens.

It's all about PV = nRT, baby.