the systems has basical a 3 switchs, the one you turn it on with ,, after that it has a low side , which wont let it come on in the event its low on charge, and a high side, when pressure gets to high
thus the cycling you hear while the unit is running, if the system goes to what i call a high side pressure , meaning its high pressure all the time. but you will need gauges to see,
either one of those switches could be bad or there is no 12 volt going to the ac unit itself