With the coming of spring and warmer temperatures, also comes the time to turn on the AC unit for the first time of the season. If you are like most people, you cleaned and changed your filters last fall, so you aren't anticipating any issues as you flip over the thermostat. Unfortunately, that's not always the case. The following are some relatively common reasons why your AC may be failing to cycle on after being off for awhile.
Issue #1: A tripped breaker
It's not uncommon to have a power outage or two during harsh winter weather or early spring winds. Major issues with the outages and related surges rarely affect the AC, since it is turned off and not receiving direct power. They can affect the breaker, though. The reason you don't notice right after the outage is because the AC is usually on its own circuit, so nothing else is affected if it flips off. Simply check and reset the circuit breaker if necessary to get your AC running again.
Issue #2: Debris in the exterior unit
The condenser coil is located in the exterior unit of your AC, which is usually located on the side of the house. If air can't flow freely around the condenser, then cooling suffers. In some cases, the condenser may even fail to work, or it will overheat, causing the AC to switch off. Leaves and other debris often blow into the vent openings on the sides of the exterior unit, inhibiting air flow. With power turned off to the unit, remove the cover from the exterior unit and remove any debris. You can even rinse it out with a hose. This will often solve the issue.
Issue #3: Thermostat failure
A failed thermostat can be another issue. First, check that the thermostat has both the AC and the fan switched on if these are on separate switches. If it does, then play with the temperature setting. Try turning the thermostat down all the way to see if that turns the AC on. If it does, then your thermostat either needs to be replaced or reset, as it isn't reading the ambient air temperature correctly. If you use the same thermostat for the furnace, check to see if the furnace switches on. If it does, then the issue may be with your AC condenser or the motor, as opposed to the thermostat.
For more help, contact an AC repair contractor in your area.