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Is your air conditioner not shutting off? This common cooling system problem eventually leads to extremely cold temperatures and a waste of electrical power.

Increasing electrical bills and worn-out electrical components are the most obvious signs of a faulty air conditioning system. This can happen due to faults in the AC system parts such as clogged, dirty air filters, frozen evaporator coils, a faulty thermostat, old condenser coils, a constantly working blower fan and other HVAC system issues.

In these cases, it is best to hire professional help to resolve the issue. However, you need to know the possible reasons why an air conditioner won’t turn off to find the correct solution.

So, if your air conditioner won’t shut off, read on!

9 Reasons Air Conditioner Won’t Turn Off

Woman Checking Ac Filter

1. Wrong Thermostat Temperature Settings

Most often, the problem doesn’t lie within the air conditioner; instead, it occurs due to incorrect thermostat settings. If your thermostat fan settings are not set properly, the air conditioning system will keep working for hours. This can happen in two ways:

a) Someone Else Has Set The Desired Temperature

Most people have their air conditioners set at a particular thermostat temperature so they know when to expect the AC unit to turn off. However, a guest or outsider might often lower the current room temperature, which makes your AC system work longer than what you would consider normal.

b) Blower Fan Runs Continuously

Sometimes, people confuse the running system fan with the cooling cycle of the air conditioner. This is quite understandable since the blower fan runs both during the cooling cycle and between each cycle, producing alternatively cold and warm air. With the thermostat fan set to ‘on,’ only the system fan will keep running even when the cooling cycle is off.

Changing Tempreture Ac

2. Faulty Thermostat

The thermostat wiring loses efficiency and gets damaged over time, disrupting the link between the HVAC unit and the cooling system. And dirt and grease sticking to the temperature sensors can make it difficult for the thermostat to detect the desired temperature of the room.

Additionally, damage to the electrical wiring and connections can stop your aircon from functioning properly.

3. Dirty Condenser Coil And Unit

Dirty Clean Aircon

The outdoor condenser unit helps the refrigerant to release heat into the air, so the condenser fins must be free from dirt, leaves, or debris. When there is a significant obstruction in the condenser unit, the airflow is restricted, which makes the air conditioner work harder to pass the air.

Similarly, dirty condenser coils prevent the compressor from releasing heat after the refrigerant passes through. Dirt, dust, or grime reduces the surface area of the coils, which restricts their proper functioning.

4. Electrical Faults

Several electrical malfunctions can lead to air conditioners not turning off properly. It can either be a faulty relay switch that disrupts electrical power or a completely damaged compressor contactor that requires replacing. Fixing a stuck relay switch is possible, although replacing it with a stronger connection is better. Check the circuit board for more issues.

5. Fan Limit Switch Not Working

Often, correct fan settings don’t prevent the fan blades from running when the cooling cycle is off. This is due to a faulty fan limit switch interrupting communication between the fan and thermostat. When the fan limit switch is stuck at the closed position, the fan blades will continue to get power even if the air conditioner has reached the set temperature.

6. Frozen Evaporator Coils

If your air conditioner is circulating hot air instead of cool air, you may have frozen evaporator coils in the indoor unit. Usually, the heat absorbed from the circulating refrigerant is released through the air conditioner’s outdoor unit. However, if an evaporator coil doesn’t receive enough heat energy, a layer of ice forms over it, which causes the air conditioning unit to become frozen.

A frozen evaporator coil is often the result of a clogged drip pan and the drain line that holds moisture in the cooling system until it turns into ice.

7. Dirty Air Filter

A dirty air filter prevents air from freely flowing through the air conditioner, which makes it challenging to produce cool air to reach the set temperature. A clogged air filter forces the air conditioner to run longer to meet the temperature demands. So, ensure that your air filter is regularly cleaned, especially before the active use of the air conditioner.

8. Low Fan Speed

The fan blades can slow down with time due to dirt build-up, forcing your air conditioner to work overtime. Also, the air conditioner works longer if the fan setting is too low, taking more time for the cooling cycle to produce cool air.

9. Low Refrigerant Levels

Every air conditioner has a specific level of refrigerant that helps spread the heat released by the evaporator coils. If the refrigerant levels become low due to damaged coils, leaks in the refrigerant lines or malfunctioning components can slow down cooling cycles. Due to this lack of refrigerant, the air conditioner runs for hours to circulate cool air faster.

How To Address These Air Conditioner Issues

Man Replacing Aircon Filter

1. Adjust Thermostat Fan Settings

If your air conditioner doesn’t shut off, try changing the thermostat fan settings to a higher temperature than the current set temperature. This will trigger the air conditioning units to shut off the thermostat and air handler.

2. Change Fan Settings

Since it is often the blower fan running instead of the cooling cycle, try changing the thermostat fan setting from ‘ON’ to ‘AUTO’ so that the fan only runs when the air conditioner is working.

3. Clean The Blower Fan

A dirty blower fan is a common reason air conditioners won’t shut off. To resolve this issue, unscrew the blower motor assembly and carefully remove it from the outdoor unit. Then, use a soft brush to clean the debris on the fan blades.

4. Remove Air Flow Restrictions

Since the air conditioner often runs longer with obstructions in air flow, remove or resolve any issue preventing indoor air circulation. Clean the dirty air filter and clogged outdoor condenser, as condenser coils release heat and install more air vents if the room doesn’t have proper ventilation. You can also consider new air filters to improve the quality of the cool air produced.

Fix The Mystery Of Why Your AC Unit Won’t Turn Off

Identifying the main cause of air conditioner malfunction goes a long way in finding a solution. However, resolving issues that prevent the air conditioner from shutting off in many cases requires replacing machine components such as condenser coils, evaporator coils, electrical wiring, the air filter etc.

Precision Electrical & Plumbing has a team of highly-experienced professional electricians based in Melbourne who is experts in air conditioner repair. With advanced tools, speedy response and premium customer service, we can resolve all your electrical emergencies in the blink of an eye.

That’s all for our guide on why your air conditioner won’t shut off. You can learn more about your AC by checking out our article on expert tips and tricks. See you next time!

Photo of Justin Morris



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