Your thermostat is the primary control for your air conditioning system and is what signals the system to turn on and shut off. Most thermostats will make an audible clicking noise each time they signal your AC system to start and stop. Although rare, there may be times when you will hear your thermostat click but your AC won’t turn on. If you ever find yourself in this situation, here are the possible causes and how they can be fixed.

Faulty or Malfunctioning Thermostat

If you hear your thermostat click and your AC doesn’t immediately turn on, it usually indicates that either the signal from the thermostat isn’t reaching your system for some reason or that there is some issue preventing your blower or outdoor AC system from turning on. If your thermostat clicks repeatedly and your AC doesn’t turn on, it usually indicates that the problem is related to the thermostat itself and could be caused by either an issue with the thermostat relay or the system’s wiring.

When the thermostat detects that your AC needs to turn on, its relay sends an electrical signal to both the blower and the outdoor condenser system. This relay is what makes the clicking noise whenever it activates and signals your AC to run. If the thermostat repeatedly clicks, it indicates that it is continually trying to send the signal but the signal isn’t getting through. The only way to know why this is happening is to have an HVAC technician inspect the thermostat relay and wiring. In some cases, the solution may be as simple as repairing or replacing the wires or tightening an electrical connection. However, if the relay is bad, you will need to have your thermostat replaced.

Malfunctioning Control Board

The HVAC control board is located inside your home and is what receives the signal from the thermostat and then sends the command for both the indoor blower and the outdoor condenser system to turn on and off. As with any other AC component, the control board can fail or start to wear out. When the board starts to wear out, it will often experience electrical glitches that prevent affect its internal relay and cause it to malfunction or timeout.

This relay is how the control board signals everything to start. If the relay malfunctions, neither your blower nor your outdoor system will start. Your thermostat will still click whenever it signals the air conditioning to run, but nothing else will happen. When the relay times out, you will also often hear the control board make a clicking sound a few times as it tries to signal the blower and condenser to turn on.

The only way to know if the problem is related to the control board is to have a technician inspect and test it. There is a chance that the control board has a loose electrical connection or damaged wire. However, if the board itself is faulty or burnt out, you will need to have it replaced. Replacing a control board isn’t all that difficult compared to some other AC repairs, but it is still something that you definitely can’t do on your own.

Broken AC Contactor

The contactor is located in your outdoor AC system and is what receives the signal from the control board and, in turn, signals the condenser system to start running. If the contactor is faulty or worn out, the system won’t ever be able to start. In this case, your thermostat will typically only click once since it has no way of knowing that the outdoor system didn’t start. Depending on how your system is set up and the specific systems you have, your blower motor may or may not still run when a broken contactor prevents the outdoor system from running.

This is a problem you may be able to easily diagnose on your own by listening to the outdoor system when it tries to start as it will also make a clicking sound. If you hear the system click but it doesn’t produce any other noise, it most likely means the contactor is bad. In this case, you will need to have it inspected by a technician and either repaired or replaced.

Worn-Out Start Capacitor

Many AC condenser systems have start capacitors that provide an instant jolt of electricity to help the system turn on. This is important as ACs typically require around three times as much electricity to start as they use once running, and this additional power draw could overload the circuit and trip the circuit breaker. The easiest way to think about the capacitor is like a battery that helps both the AC compressor motor and fan motor to start. Just like a battery, capacitors can slowly lose their ability to store a charge, and this will usually prevent your outdoor systems from turning on.

This is another problem you can check for by listening to the system when it tries to start. A faulty or worn-out capacitor will often cause the system to repeatedly make a clicking noise. You will also hear an audible humming sound, which is caused by the systems motors attempting to start on their own without the additional power from the capacitor. Luckily, having a technician replace a worn-out capacitor is a fairly inexpensive and easy fix compared to many other AC problems.

The AC blower inside your home may also require a start capacitor in order to turn on. In this case, it could have its own capacitor or it may rely on the capacitor in the outdoor system. If your thermostat clicks and your outdoor system turns on but the blower doesn’t, you should shut the system off and then listen to your blower once the system is back on and tries to start. Again, if the blower capacitor is faulty, you will usually hear it click multiple times and also a humming noise coming from the motor.

Clicking noises aren’t the only thing you need to worry about. Buzzing, humming, rattling, grinding, hissing and other unusual noises are also signs that there is some problem with your AC system. If you do ever hear your AC making any strange sounds, we would recommend shutting the system off and then immediately contacting an HVAC technician to inspect it. This is because many of the issues that can cause your system to make these noises have the potential to ruin either the blower motor or the condenser if left unchecked. What may have started out as a small issue could quickly turn into something much bigger that requires expensive repairs or for you to replace one of your systems altogether.

If your air conditioning won’t turn on, is making loud noises or has any other issues, you can trust the team at Hitchcock Heating & Air for help. We repair and service all types and brands of air conditioners, and we can also assist if you’re looking to upgrade or replace your old system. We also offer a full range of heating and indoor air quality services, and we work on both residential and commercial HVAC systems in Rome and the surrounding areas. For more information or to schedule any cooling or heating service, contact Hitchcock Heating & Air today.

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