The first thing that needs to be checked is the pressures in the system. Without the proper pressure, the AC system will not come on.
Do you have a set of gauges to check the high and low side pressures?
I attached a wiring diagram for you. There is nor relay. The control head sends power to the compressor when it gets the correct signal from the pressure switch.
Images (Click to enlarge)
Tuesday, April 30th, 2019 AT 4:17 PM