[brcidd]

First of all, your "switch" is a pressure transducer-used for variable measurement of system pressure- there will be "no continuity"- just a variable voltage feedback to the ECM. You know it is not a switch because it has three wires. NEVER jumper a three wire transducer, you can cause ECM damage. Pressure transducers were introduced in mid to late 90's on most cars....

Yes you can add refrigerant without coolant fans and without compressor running. Again, static pressure is your key- once you attach refill kit gauge- you'll know what your static pressure is-- from here I'm betting it is below 47 psi, at a warm ambient-say 70 degf or so. If this is true, then you have about 3 or 4 ounces in your 2+lb system. So adding a whole can should make the compressor engage.