Does a 1996 Lincoln Towncar low pressure sensor sense Low and High pressure or just Low pressure?

I misstated above; Compressor will run if I jump across the low pressure switch.

Are you sure you have 55 psi? Are you using store bought can with hose or manifold set? And is this static pressure or dynamic pressure? And what side? Did you vacuum down and add can or just add can? You could have a bunch of air in system. Did you test the switch? Once compressor does engage the low side pressure decreases. What does it plateau at when car is running and clutch is running? Be careful jumping this if system is really too low to engage it by itself as you can burn up compressor

Have you checked relays and fuses?

Thanks for your replies. I replaced the low pressure switch, vacuumed system, recharged and all is good now. thx