ARB Tire Inflator

[Jeeper Creeper]

I just bought an ARB Tire Inflator (ARB605) to air up my tires. As soon as I hook the hose up to my power tank I hear air escaping from the end where it connects to the valve. Once the end is connected I don't hear the air any more since its probably going into the tire. The real problem is when I pull the trigger to put air in the gauge jumps up to 60 sometimes 80 pounds....and when the trigger is released the it drops back down to zero. Is this a defect, I thought I could inflate to exact pressure by watching the gauge, but its way off because when checked with another gauge the pressure is actually down to 20 or 30 pounds.