Originally Posted by christuna

There should be 2 switches - one for the fan and one for the pressure (its 2 function - it will open if the pressure is too low or if the pressure is too high)

The pressure switch is on the "high" side of the ac system and it's either open or closed so don't look at resistance but look at continuity.

If everything is ok it should be closed. If the pressure is too low or too high it should be in the open (no continuity).

110psi the switch should be closed.

It should open if it's below ~30psi and it should also open if it gets above ~300psi