It will need to be put on vacuum Frank, even more so if any pipe ends were left open to the air. You have to get the air and moisture out before the refrigerant goes in. If not you are trying to refrigerate with a mix of refrigerant and air and any moisture will freeze in your orifice (and you dont want that now do you!). The drier is only there to take the last bit of moisture out, not all and it itself will be absorbing moisture as soon as it is fitted/opened to the air.
Evacuating will not show minor leaks, it is a blunt instrument for leak detection as it is vacuum rather than pressure and only ever a maximum of 14.7 psi from the outside in. You may see a pressure rise from vacuum which could either be a leak or moisture boiling off. Charging after vaccing out with dry nitrogen to operating pressure and leaving for a time will show up leaks. The longer you leave it, the smaller the leak it will find as this is based on the gauge showing a drop in pressure.
The cans are OK for topping up but they contain oil and you can easily over charge a system with refrigerant, oil or both. Besides, if you have the right level of the right oil in the system (I can't remember but did you drain any remaining oil from the rest of the system as you might end up with too much oil?) then having the right level of refrigerant in the system will be another certainty rather than a variable.
There's nothing mysterious about anything if you know all about it and how to fix problems without creating others.
As with everything else on these trucks, do it right and you sleep better.
Evacuating will not show minor leaks, it is a blunt instrument for leak detection as it is vacuum rather than pressure and only ever a maximum of 14.7 psi from the outside in. You may see a pressure rise from vacuum which could either be a leak or moisture boiling off. Charging after vaccing out with dry nitrogen to operating pressure and leaving for a time will show up leaks. The longer you leave it, the smaller the leak it will find as this is based on the gauge showing a drop in pressure.
The cans are OK for topping up but they contain oil and you can easily over charge a system with refrigerant, oil or both. Besides, if you have the right level of the right oil in the system (I can't remember but did you drain any remaining oil from the rest of the system as you might end up with too much oil?) then having the right level of refrigerant in the system will be another certainty rather than a variable.
There's nothing mysterious about anything if you know all about it and how to fix problems without creating others.
As with everything else on these trucks, do it right and you sleep better.