276 Freon charge

When recharging a compressor that isn't a new install or hasn't been evacuated and vacuumed down you will add much less than that. In fact, unless you actually use a scale AND watch the low side gauge you won't even know how much freon it takes to get it to the proper level. The way to add gas is by using the low side pressure as your guide. In a properly functioning cooling unit with a clean condenser, properly functioning evaporator and condenser fan motors, no ice on the evaporator and good valves in the compressor (not known until you try charging it) you will add gas in short bursts until the low side pressure is between 18-20 lbs. You have to add gas and let the system equalize itself while watching the gauge. Then add more if needed, maybe several times until you either reach a stable correct pressure or you determine that the valves are bad. Bad valves will show up as pressure that fluctuates in slow, wide sweeps that don't stabilize, pressure that goes way high quickly such as to 35 lbs or more with little added gas, pressure that won't rise at all with several bursts of gas, or a cold, frosty (not cool) accumulator. If you seem to reach the proper low side pressure and then find ice on the evaporator at a later time you need to see if the low side has suddenly risen above 20 lbs. This would be due to bad valves. Bad valves also exist if you have tapped a system for the first time and found the low side pressure above 20 lbs because the factory will not have overcharged the compressor.