Your air conditioning system represents more than a century of technology advancements and refinements. This long history means the components are remarkably reliable, but from time to time things can go wrong.
Let’s look at five common AC problems and a few basic troubleshooting tactics. Keep in mind that if the temperature is rising and your blood pressure is too, the smart course of action is to contact your AC service company.
1. The system won’t come on.
This is one of the most common reasons for HVAC service calls, but it can be one of the easiest problems to fix. Why? Often the issue is (ahem) the operator, not the system. Common mistakes include setting the thermostat to “off” instead of “cool” or setting the desired temperature so high, it’s higher than the indoor temperature. Sometimes it’s a simple power issue. Check to see if the circuit breakers have been tripped for the AC unit and the air handler (blower), and if necessary reset them.
2. There’s little or no air coming out of the vents.
If your AC system is on but there’s little or no air flowing from the vents, there are several possible causes. Examine the air filters and if they appear dirty replace them. Dirty filters restrict air flow, hamper the system’s performance and can cause the evaporator coil to freeze. A faulty thermostat, failing blower motor or burnt or broken wires can also cause low or no air flow issues.
3. The air coming out of the vents isn’t cool.
If the system is running, but the air coming out of the vents isn’t cool, the problem may be the evaporator coil. Replace dirty filters, which can restrict air flow and can cause the coil to frost. If the filters are clean, go to the thermostat. Switch the setting from cooling mode to “fan only.” Let the fan run for several hours to defrost the coil, then reset the thermostat to “cool” to test the system. If the air flow is still warm, you might be low on refrigerant or need to have the evaporator coils cleaned.
4. The compressor won’t come on but the outdoor unit fan runs.
A variety of problems can affect the compressor. If the outdoor unit fan runs but the compressor won’t come on, one of the wires or connections at the compressor may be burned, broken or shorted. Other likely causes include a failed capacitor, a bad contactor or a short in the compressor, problems that are best handled by a pro.
5. The compressor and outdoor unit fan won’t run.
If neither component will run, check the basics first. Confirm a power surge hasn’t tripped the circuit breaker and if necessary reset the switch. Make sure the thermostat is set to “cool.” If the unit is receiving power, the AC is on at the thermostat but the components won’t function, the problem may be broken or shorted wires, a failed contactor or a faulty thermostat.