I'm replacing the pressure switch on a old air compressor and it has 4 screws L1 T1 t2 L2 how do I wire.

Hi,
I believe you have not received an answer is because there is too little information. How about a brand and model, or something to clarify the question.
Normally one makes a diagram of the wiring before disconnecting anything.
Peace,
Clarke

L1 and L2 are the terminals the line or feed will connect to, leaving T1 and T2 for the leads to the motor.