Hi. Does anyone know how to jump the A/C pressure switch to see if the system is low on refrigerent?

I've a 1996 4Runner 3.4lt gas. Any help would be appreciated as I live in an isolated area and don't have ready access to pressure gauges etc.

 

I've just looked at the wiring diagram from my 2001 4Runner and on that it looks like the pressure switch is normally closed, but opens when pressure is either too high or too low. It's actually 2 switches in one. On mine it has an orange and blue/black wire, if you connect them it should bypass the switch. Another option is connect +12V to the compressor clutch, which on mine is a white/green wire.

All this is based on an 01, I don't know if a 96 is the same.