Air conditioners only have two settings -- on and off.* If it comes on and works like it should when it's on, but isn't coming on reliably, it's usually the thermostat. It's amazing how awful programmable thermostats are. I had one that started short cycling the a/c by running it for six seconds every time it cut on or off. Another one had a bad switch that didn't reliably make contact on A/C mode. Both developed these problems within a year.
*I know some new high efficiency A/Cs actually have two stages.
Touch the intercooler on a modern turbo'ed car. You'd be surprised.