Click! Click! Click-click! CLICK!

It’s not that loud, but it’s driving you crazy. Especially when you don’t know what’s happening. So why does your thermostat keep clicking, and what can you do about it?

I’ve put together a list of reasons for the clicking and possible solutions. So read on in hopes of finding the peace you once took for granted.

Why Does Your Thermostat Click?

First off, in some circumstances, it’s quite normal for it to click. Remember, your thermostat is a communication device. (No, I’m not saying it’s talking to you in its own language)

thermostat
Various things can make your thermostat click, read on for more information.

When your indoor temps fall below or exceed your set temperature a message is sent to your furnace or air conditioner to kick in. Your thermostat has a relay that needs to open and close, sending power to the necessary appliance so it can respond with the necessary cool or warm air.

The clicking is the sound of that relay switch opening and closing. It’s purely mechanical.

So if that’s all you’re hearing, just a click-click as your HVAC cycles on, it’s normal. Either get used to it or go somewhere where you can’t hear it.

But what about when it clicks incessantly? Let’s see if we can save your sanity by pointing out some probable causes and solutions. The good news is that in some cases you should be able to solve the problem yourself.

Clicking Thermostat Causes and Solutions

As mentioned above, some issues are simple and easily remedied. I’ll run through them first and then get to the more problematic and potentially serious issues.

Battery Powered Thermostats

Do you have a battery-powered thermostat? Then constant clicking may be an indicator of dead or dying batteries.

Solution. I shouldn’t have to say this, but here goes. Replace your batteries and monitor the clicking situation. If it has stopped, you have found and solved your problem.

Thermostat Placement

When your home was built and your HVAC and thermostat installed, your thermostat would have been placed in the optimal spot. At least it should have been.

The optimal spot is somewhere where it can correctly sense room temperature. This means it’s not in the path of direct sunlight, drafts from windows or vents, too close to a bathroom or kitchen that gives off heat, and much more.

If your thermostat is placed anywhere where it’s picking up rapid changes in temperature, such as the following, it needs to be moved.

  • Someone standing with the fridge or freezer door open too long
  • A hot oven
  • A hot shower or bath
  • Hot or cold forced air via the supply vents
  • Direct sun appearing and disappearing behind clouds

Any of these situations can cause the thermostat to start clicking as it’s impacted by changes in room temperature.

Solution: Move the thermostat to a more desirable location. As central in the home as you can manage, not in a corner. And away from any of the issues mentioned above.

A Loss of Power

Your thermostat could be calling for hot or cold air and not getting it. The clicking is the relay trying again.

Solution: Check your circuit breaker for a tripped circuit. You could have power to your thermostat—especially if it’s battery-powered—but not to your furnace or air conditioner.

If your breakers are all okay, check the appliances themselves. Make sure the pilot light is on in the furnace, and that all plugs are secure in electrical outlets.

An Interrupted Gas Supply

If you have a gas furnace, your thermostat could click if it called for heat but didn’t get a reply.

Solution: Make sure your gas supply is switched on and that the furnace is plugged in. If you smell gas, turn the supply off and call an HVAC pro right away.

Dirty Filters

It seems like such a simple thing, but dirty filters can cause more damage than you might imagine. Blocked airflow is detrimental to your system in a variety of ways and may start your thermostat clicking because your system is short cycling.

dirty air filter
Clean and replace your air filters regularly to avoid HVAC issues.

Solution:  In most cases, filters need to be changed every one to three months. Depending on your household, pets, allergies, and other factors, you may be able to get away with only changing your filter in longer cycles.

Dirty Condenser Coil

The condenser coil is located in the outside unit of your air conditioner. It’s just behind the fins or metal wiring that covers the unit.

If the fins get clogged with dirt and debris, it will obstruct airflow. Just as in the scenario above with clogged filters, a lack of airflow can cause your system to start short-cycling, which in turn can cause a clicking thermostat.

Solution: Head outside and do a walk around your air conditioner. Inspect for any obvious damage first. Use a coil cleaning brush to clean the coils and then a fin comb to straighten out any bent or warped fins. You should be able to find a set like this one at your local Amazon.

The next step is to lightly hose down your coils. Once wet, spray a generous amount of foaming coil cleaner on the coils. It will go to work and lift dust and debris from the coils. Note that depending on the type you use, you may not have to rinse it off. So follow the directions on the can.

It’s a good idea to make this a yearly maintenance project. Either at the beginning or end of the cooling season, whichever works best for you.

Dirty Pilot Ignitor

If the pilot igniter sensor in your furnace gets clogged it will fail to respond and fire up the furnace. Because the thermostat isn’t getting a response, it will continue to click until it does.

Solution:  First, if you have a newer furnace, you don’t have a pilot light, so move on.

Before you start to clean the ignition sensor either unplug it or turn off the breaker. Remove the screw that holds the sensor in place and lift the sensor out, being very careful with it.

Once you have it in hand you want to clean it with a fine grit sandpaper to remove any buildup of grease and dirt. Then wipe it down with a clean paper towel and replace it and the screw.

Cracked Mercury Bulb

Since we’re talking about mercury, it should be obvious that we’re talking about the old-style round thermostats. If you take the faceplate off, you can see a little bulb. They’re called tilt switches. Mercury is a neurotoxin and a cracked bulb is dangerous.

old thermostat with mercury bulb
Dispose your old thermostat and replace it with a programmable switching

Solution: Properly dispose of the thermostat and buy one with electronic programmable switching.

When the Situation May be More Serious

Now let’s talk about some of the more serious reasons behind a clicking thermostat.

There can be times when a constantly clicking thermostat isn’t the problem of the thermostat itself. It’s simply registering that there is a problem somewhere else in the system.

Run Capacitor

The run capacitor keeps the motor running smoothly. No jerky movements, no up and down spikes in power. A bad run capacitor may be the culprit if your air conditioner turns on and then right back off.

Solution: Have someone stand out by the compressor. If the AC turns on and right back off at a call for cool air, shut it off. You’ll need to call an HVAC pro as the part will need to be replaced—if possible.

Other Electrical Issues

I covered some power issues above, but if you can’t find the problem, there may be a faulty wire somewhere in your circuitry.

Solution: Call an electrician.

Conclusion

As with so many HVAC problems, there are many reasons why your thermostat might be clicking. Some of them are simple fixes and some are cause for concern.

Solutions range from changing batteries or filters to needing an HVAC pro or electrician. But hopefully, the info above can point you in the right direction. And ultimately save you some money.

Thanks for reading! Do you have any other questions or concerns? Why not check out our related articles below?