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Air Conditioner Thermostat Troubleshooting & How To Fix

As we hurtle towards what is a scorching summer period for most of us in Australia, many of us will retreat indoors in the hottest part of the day to enjoy the cooling bliss of an air conditioner. Air conditioners — both split and ducted systems — consist of piping and lines, outdoor and indoor units, airflow outlets, and various connections and controls. And each of these components can eventually start underperforming or breaking down.

One of the elements of an air conditioning system that can cause a lot of problems is the thermostat. Here is our guide to air conditioner thermostat troubleshooting, including what can go wrong and whether you can find a DIY solution or not.

What air conditioner thermostats do

We rely on the thermostats in air conditioning systems to give us accurate temperature readings and ensure the required adjustments to the air conditioning unit’s temperature are made. Essentially, if the thermostat is not working correctly, you cannot effectively communicate with your system and your comfort levels and the unit’s energy efficiency could be compromised.

Air conditioner thermostat location

In terms of air conditioner remote control symbols, many models have visually similar symbols. (Check out our blog — What Every Daikin Air Conditioner Symbols Means — for a guide). In terms of the air conditioner thermostat location buttons on your remote, the two important ones to refer to are:

Air Conditioner Remote Buttons

General air conditioning issues

Most of the common air conditioning problems and solutions apply to any type of system, but some are specific to each, whether it be a split or ducted system. Here are the top 6 air conditioning issues:

Signs you may have thermostat issues

There is a range of issues that can indicate problems with AC thermostats, usually evident in noticeable external signs, including:

Your unit is not cooling or heating properly

One of the most common air conditioner issues is units that are producing air that’s inconsistent with your chosen settings. Air conditioners are meant to provide a consistent air temperature, and if your system stops producing warm or cool air when you need it, it could be due to a range of issues. Possible causes are:

The above can all result in your AC system not cooling your property sufficiently or at all! Most of them can also lead to overheated interior AC units.

In terms of solutions, you can fix some non-technical issues yourself. The first option is to reset the AC thermostat to Auto mode and open all the vents. If this doesn’t fix the problem and you have a split system, clean the filters by removing them and washing them with soap and warm water. Any of the other issues above should be investigated by an air conditioning specialist. Filters on ducted units are also not typically accessible to homeowners, so again, contact a professional.

Your unit won’t turn on

This issue can be frustrating, particularly if it happens unexpectedly and it’s a scorching hot day outside! Possible causes are:

Some of the causes behind your AC system not turning on can be simple and easy to fix yourself, whereas others will definitely require the expert skills of a licensed professional. First up, check the batteries in your temperature control devices and replace them if necessary. If that doesn’t work, check the thermostat settings are as they should be (for example, in the Cooling mode and at the desired temperature).

It’s also worth checking that the outdoor condenser is running, as sometimes lowering the temperature by around ten degrees can resolve the issue. However, programming and calibrating thermostats can be tricky, so we definitely recommend you contact your air conditioning technician.

Your unit won’t turn off

The central AC system is designed to turn itself on and off via the thermostat. So, if it fails to do that, there is a problem. Possible causes are:

The only DIY solution with this issue is switching your system off by turning the thermostat fan to the “off” mode. If you still can’t turn the system on again, then it is a gas or electrical-related issue that needs a professional.

How to fix an ac thermostat

We have offered some solutions on how to fix an AC thermostat above. However, it’s worth mentioning that anything other than simple maintenance (like cleaning filters, vents and outdoor units) shouldn’t be attempted by yourself. This is because DIY troubleshooting carries more risks than benefits. Risks include:

So in terms of air conditioner thermostat troubleshooting, our advice is to call in an expert. If you have done your general cleaning maintenance and still have an issue, it’s more than likely it is something more serious that requires professional servicing.