Your home air conditioning system has a number of expensive and complex components. A failure in any of these key pieces can result in the entire system failing to function properly. Ironically, many common issues originate with one of the simplest and least expensive elements of the entire system: the thermostat. If you believe one of the thermostats in your home is to blame for an AC system that is not operating as it should, this checklist will help you to diagnose the problem.
Are Your Vents Blowing Cool Air?
No matter how fancy your thermostats happen to be, they are essentially simple on/off switches for your air conditioner. The temperature that you set on the thermostat is the maximum allowable temperature for the zone controlled by that thermostat. If the temperature is higher, then the air conditioner engages. If it is lower, the air conditioner shuts off.
Since your thermostat does not control the temperature of the air produced by your system, a failing thermostat will not result in warm air. If you feel only warm or room temperature air, then you may have a more serious issue with your compressor or another component.
Is the System Short Cycling?
Short cycling is a condition where your air conditioner turns on and off more often than it should. In extreme cases, the system may short cycle every few minutes or even more than once a minute. If your thermostat is malfunctioning, it may repeatedly signal your compressor to engage and disengage, resulting in a short cycling condition. This puts a great deal of strain on your compressor and blower, so it is important to address short cycling issues as soon as possible.
Short cycling does not always indicate a problem with a thermostat, but it should be the first suspect after confirming that the filter is relatively clean and unclogged.
Does the System Turn on At All?
If the system suddenly stops functioning, then there's a good chance that the thermostat is to blame. Failing compressors usually provide some warning before they give out entirely, so if there were no additional symptoms then it is likely that your thermostat is no longer properly signaling the compressor to turn itself on. Always check your circuit breaker first, but if the breaker has not been tripped then the thermostat should be considered the primary culprit.
Thermostats are fairly trivial to replace, but it is a good idea to contact an air conditioning service in any situation where your system is not functioning properly. A technician can thoroughly investigate the problem to confirm that the cause is not something more serious, saving you time and money.