The disconnect.
The small box on the wall beside the outdoor unit. It cuts power to the condenser, and it is not a thermostat.
The disconnect is the small grey box mounted on the wall within sight of the outdoor unit. Inside is either a pull-out handle or a switch, and its only purpose is to let somebody working on the condenser kill power to it and know for certain nobody can turn it back on from inside the house.
Code requires one within sight of the equipment for exactly that reason.
Disconnect, breaker, thermostat
Three different things that get confused.
The breaker is in your electrical panel and protects the circuit. If it trips repeatedly, something is drawing more current than it should and that is worth diagnosing rather than resetting.
The disconnect is the local cutoff at the unit. It does not protect anything, it just isolates.
The thermostat is the control. It is the one meant for daily use.
Do not use it to cycle the system
Pulling the disconnect to turn the AC off, and pushing it back in to turn it on, skips every protection the control board has, including the delay that stops a compressor restarting against high head pressure. Doing it repeatedly is hard on the compressor.
The one time it is genuinely useful: if you see ice on the lines or smell burning and want the outdoor unit stopped now, pulling the disconnect stops it. Then call somebody.
It can be the fault
Pull-out disconnects corrode and their contacts pit, exactly like a contactor. A condenser that is dead with a live breaker is worth checking here before anybody opens the electrical compartment.
What it looks like going wrong.
The AC is running, but the house isn't cooling.
Air is moving, the house is climbing, and nothing has tripped. Here is the order to check things in.
Read itA capacitor is the cheapest thing that stops an AC.
Humming, a fan that will not start, a unit that trips on the hottest afternoon of the year. Usually a part the size of a soda can.
Read it