The low pressure switch.
A safety that stops the compressor when suction pressure falls too far. Usually reporting a leak.
A low pressure switch sits on the suction side of the refrigerant circuit. If suction pressure falls below a set point, it opens and stops the compressor.
Its counterpart is the high pressure switch on the other side of the system.
What it protects against
Running a compressor with very low suction pressure is bad in several ways at once. The refrigerant that carries oil back to the compressor is not flowing properly, so lubrication suffers. The compressor runs hotter, because refrigerant flow is also what cools it. And a system that has lost most of its charge can pull a vacuum on the low side and draw moisture in through any opening.
So the switch stops it.
What makes it trip
A refrigerant leak, which is the common one. A sealed system does not consume refrigerant, so low means a hole. Often called a loss of charge switch for exactly this reason.
Restricted airflow across the indoor coil. Less heat reaching the refrigerant means less of it boiling off, which means lower suction pressure. Filter, blower wheel, closed vents.
A TXV stuck closed, starving the coil.
A blocked filter drier restricting the liquid line.
Genuinely cold conditions, which in Phoenix means running cooling on an unusually cool night rather than a real fault.
The pattern
Low pressure trips frequently present as short cycling: the system runs, pressure falls, the switch opens, the system stops, pressure equalises, the switch closes, and it starts again.
If the cause is a slow leak, the cycling gets worse over weeks as more charge leaves. That progression is itself diagnostic.
Why not to bypass it
Same answer as every other safety on the system. Jumping it to keep the house cool means running a compressor without lubrication or cooling, and that turns a leak repair into a replacement conversation.