Thermostat Clicks But AC Does Not Turn On? 3 Easy Fixes

It can be rather frustrating, especially in the summer months, when your AC just won’t turn on no matter what you do.

If you hear that the thermostat clicks but AC does not turn on, this can actually indicate a few issues with your air conditioning. Luckily, they’re usually quite easy to detect and fix permanently.

In this guide, we will show you the easiest methods of troubleshooting your AC unit, which will help you detect the core issue, as well as the best methods to solve these problems.

Why does the thermostat click but AC does not turn on?

In most cases, you will hear a loud clicking sound coming from the thermostat, but the air conditioner will simply not turn on.

If this is the case with your AC unit, there are a couple of possible scenarios you should look into before you decide to repair it yourself or contact a professional (depending on the severity of the issue).

1. Faulty control board

The connection between the control board and the thermostat is crucial when it comes to the functioning of your air conditioning.

The main role of the control board, in fact, is to trigger the AC via electrical signals, which basically “notifies” it to turn on or off.

This command comes from the thermostat itself. However, if the control board isn’t functioning properly, it will not be able to receive these signals from the thermostat, nor trigger the AC unit to turn on.

It is possible that the control board of your AC unit has a faulty electrical control which causes a delay and that clicking sound you hear.

2. Defective thermostat

Sometimes, what causes an issue in your AC system, especially if the thermostat clicks but the air conditioning unit doesn’t turn on, is a problem in the thermostat itself.

It is actually quite common for air conditioners to produce a clicking noise, but it should not be too loud, and the AC should be able to turn on without delay.

If the clicking noise is quite loud, but the AC still won’t turn on, this could be due to a faulty relay in your thermostat. The role of a relay in the thermostat is to open or close the air conditioner, depending on whether you’re turning it on or off.

If the relay is defective or broken, you will always hear the thermostat click loudly.

Another possible issue with the thermostat could be old, defective, or frayed thermostat wires, which is something that should be checked during regular maintenance of your cooling system.

A bad thermostat will affect the entire cooling system, so it is necessary to have it repaired or replaced as soon as possible. 

You can also check if the thermostat is the issue by detecting where the clicking sound is coming from. If it is coming from the thermostat itself, it is likely that the issue is a bad thermostat. However, if the sound is coming from the outdoor AC unit, you should look into other elements of your cooling system.

3. Faulty contractor

A contractor on your AC unit is yet another important connection between the unit itself and the thermostat. It is located on the outside unit, and it is largely responsible for turning the air conditioner on or off.

The contractor is basically the element that triggers the compressor in your AC unit when you turn the cooling on.

A faulty AC unit contractor will be unable to receive and realize the command coming from the thermostat, which usually results in a loud clicking noise in the thermostat when the AC unit won’t turn on.

You will recognize a faulty contractor when the outdoor unit isn’t starting, but there is a clicking noise without any buzzing or humming that you usually hear.

4. Defective capacitor

A capacitor is yet another element located in the outdoor unit of your air conditioning system, and it is basically responsible for powering up the AC compressor.

It isn’t an essential component of every AC system, as some units simply do not require it to start up. However, older units will usually include them.

In case the charge in the capacitor decreases (which usually happens over time), the AC won’t have the necessary power to turn on, resulting in that clicking noise you hear, followed by a faint buzzing sound.

You will also recognize a faulty capacitor if there is some gooey material (discharge) on it, or if it has any visible defects such as bulging.

How to fix a thermostat that clicks but AC does not turn on

Once you’ve detected the core issue, it is time to evaluate whether you should contact a professional or try to repair or replace the faulty element in question yourself.

Keep on reading as we discuss some of the best methods of fixing an AC unit that does not turn on while the thermostat is clicking. 

1. Check the air filters

Oftentimes, the issue is much smaller than you may think, and it doesn’t necessarily require professional assistance.

The first step to troubleshooting and potentially fixing your AC is checking your air filters for any clogs, including dirt and dust buildup, as well as accumulated particles and debris that get in the way.

When the air filters are clogged, the airflow to your furnace or HVAC system will be disrupted, causing the thermostat to click.

Over time, the buildup can increase to a point where your system is unable to perform, causing it to fail, which is why you may be unable to turn on the AC.

It is recommended to clean your air filters regularly and replace them every 60-90 days. It is always better to invest in high-quality filters, and not only to avoid the thermostat clicking issue.

High-quality, durable air filters will protect you from air contaminants, especially if you’re prone to allergies or any respiratory issues. 

On the other hand, not changing the air filters regularly could result in contaminants ending up in your AC system, sending them back into the air you breathe.

2. Check the thermostat settings

Yet another easy yet effective method of solving this issue is adjusting the thermostat settings in case they haven’t been properly adjusted.

In many cases, the temperature on your thermostat is set too high, so the system doesn’t start until that temperature is reached. To get your AC system to start, you should set the temperature low enough for the cooling system or high enough for the heating system to get triggered.

Keep in mind that you should make these adjustments according to the room temperature. If you leave the temperature settings near or at room temperature, nothing will trigger the system to start working. 

3. Test the thermostat

As we’ve mentioned, one of the potential issues that could be causing the thermostat to click while the AC isn’t turning on is a faulty thermostat itself.

What you want to do is inspect the thermostat and look for any loose wiring, defective wires, loose relay connections, or visible damage. It is necessary to tighten the loose connection and replace all damaged wires and components. 

The next step in troubleshooting the thermostat would be to turn it off from your circuit breaker, wait for a few minutes, and then turn it back on. 

If you notice that it takes a lot of time to turn back on, or it doesn’t start at all, the problem is in the thermostat itself.

When it comes to changing or fixing the important components of your air conditioning system, including the thermostat, control board, contractor, and capacitor, we recommend hiring a professional.

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