What is the low side pressure when the compressor is jumpered and running continuously?

 

Mech
If you have not had A/C for over a year, it is safe to say you have probably lost your charge. You paper clipped around the cut off switch! Clutch came on, this says to me your charge is low. Switch protects your compressor from self destruction. One thing I do when I have switch bypassed is feel the lines. Big one is suction and if you have any coldness that says you have some 134a in system. When you added 134a and had wire plugged back into the switch you said it cycled on and off. That is normal; when you have the proper amount of 134a it will stay on for longer periods of time. When you are fully charged your accumulator will be cold with drops of water on it. The small line coming from your compressor is the high side and it will be too hot to touch. Your engine does not have to be any special temperature to charge your system
You mentioned the nut being missing off of end of compressor. There is none, you put a special tool in there to adjust the air gap on the clutch. If it clicks off and on, don't worry about it. After charging my system, it did not last very long. Had to replace compressor large o'rings had failed could see oil tracks on back half of compressor. The good thing about all this is you are trying and that is how we all learn. I am assuming you are using the single gauge for filling your unit. You leave it plugged into the suction side port, added small amounts at a time. You will notice a small adjustable red or black arrow you set this to the outside temperature you are experiencing the day you are doing this work. You than charge it in those safety zones. We like to think a little more is good. But this is not the case. George had mentioned the switch on the back of the compressor, it is to protect you from overcharge. Leave this switch alone and do not bypass!!

 

Mine is a 1999