Troubleshooting AC Unit Not Turning On (9 Issues Solved!)

Did you know that troubleshooting AC unit not turning on is mostly DIY? That’s right, and I’ll show you how to do it. But first, you ought to know what might be amiss.

Often, AC units fail to turn on due to lack of power, a faulty thermostat, a dirt-clogged filter or condenser, clogged or leaky ductwork, ice buildup, low refrigerant, failed compressor, or a dead capacitor or AC.

There are at least nine possible explanations for your non-working air conditioner. I’ll walk you through the nine issues, describing how they prevent your air con from turning on and what you can do to fix them.

So, regardless of your AC model, you can apply these tips to get it working. Before that, let me explain how an air conditioner works so you can understand how it fails.

In a rush? See below the nine issues which prevent air conditioners from turning on.

Troubleshooting Ac Unit Not Turning On – Quick Guide

–	Problem	Recommended Fix
1.	Lack of Power	Ensure the AC is plugged in and turned on. Reset the breaker if flipped off and replace the fuse if blown up.
2.	Malfunctioning Thermostat	Set the thermostat on ‘cool’ mode and replace it if it doesn’t show any continuity
3.	Dirt-Clogged Filter or Condenser	Clean the air filter and condenser if they are dirty. Replace the air filter if you cannot clean it.
4.	Clogged or Leaky Ductwork	Clean clogged ductwork, and if the ducts are leaky, replace them
5.	Ice Buildup	Melt the accumulated ice after the winter
6.	Low Refrigerant	Call an HVAC expert when you suspect a refrigerant leak
7.	Failed Compressor	Replace the compressor if it’s not working
8.	Dead Capacitor	Call an expert technician to help you inspect and fix the capacitor
9.	Dead AC	Replace the AC if you can’t fix it, or it has become too expensive to do it

How an AC Works

An AC (air conditioner or air con) employs refrigeration technology to cool your space. This appliance extracts heat from the warm indoor air and transfers it outside. Meanwhile, it circulates cold air inside to keep your room cool.

Essentially, the warm air inside goes through a return vent and air filter and passes over the evaporator coil. The liquid coolant or refrigerant then absorbs heat from it, and through the compressor’s action, the liquid coolant turns gaseous.

Overall, the gaseous coolant is responsible for keeping your indoor air cool.

How Do I Get My AC Unit To Turn On?

The process of troubleshooting an AC unit that’s not turning on starts with identifying its reason. Below are 11 reasons air conditioners fail to turn on and how to fix them:

1. The AC is Not Getting Power

It’s elementary; without power, your AC won’t turn on. So, the first check is the power supply, which brings us to these issues:

The AC might not be plugged in – Realistically, you cannot expect your AC to turn on if it’s not plugged into the power. So, check it and plug it in correctly if that’s not the case.
The AC might not be turned on – Sometimes, you might plug in the AC but forget to turn on its on/off switch. So, check this switch and turn it on if it’s off.
Blow-up fuse – The thermal fuse usually blows up when there is too much current flow. Doing so enables the fuse to protect the AC from overheating but, unfortunately, cuts off its power supply, preventing it from turning on. So, test the fuse with a multimeter and replace it if it shows no continuity.
Tripped breaker – The circuit breaker trips to protect your AC when there’s a current overload. So, check it and reset it if it’s tripped.
Loose or damaged wiring – Any loose or damaged wires could break the AC’s circuit and prevent it from turning on. If so, you’ll need an expert technician to fix it.
Bad control board – Lastly, if the control board is bad, your air conditioner won’t start. Overall, you may need a service technician to help you diagnose and fix a failed control board.

2. The Thermostat Could Be Malfunctioning

Your air conditioner could also fail to turn on due to a malfunctioning thermostat. But before you can rule the thermostat to malfunction, ensure it’s set correctly.

If the setting is correct, you must inspect the thermostat for fault to determine if it needs a replacement.

Fix

Confirm that the thermostat is in ‘cool’ mode. If not, set it accordingly. And to confirm if the thermostat is faulty, test it with a multimeter. Overall, the absence of continuity proves that the thermostat is defective and needs a replacement.

3. The Air Filter or Condenser Could Be Dirt-Clogged

The air filter and condenser accumulate dirt over time, seriously affecting the AC’s operations. Too much dirt makes it hard for air to circulate properly, and the compressor struggles to start.

The condenser is also unable to run if it’s dirt-clogged, preventing the AC from turning on.

Fix

Inspect the air filter and condenser for dirt clogging and clean them. Remember, however, that you have the option of replacing the air filter if you cannot clean it.

4. The Ductwork Could Be Clogged or Leaky

Your AC features a set of ducts that direct warm air into the unit and cold air out of it. If these ducts are dirty, there won’t be proper airflow. So, the AC won’t start.

And if the ductwork is damaged, air will leak, preventing the AC from turning on.

Fix

Inspect the ductwork for clogging and clean them and if there’s a leak, replace the ductwork.

5. Possible Ice Buildup (Winter Dormancy)

The AC will likely stay dormant during the winter since you don’t use it. Unfortunately, the dormancy period means possible ice buildup around the fan, condenser, and other parts.

The icing, unfortunately, makes it hard for these components to run and the AC to start.

Fix

Inspect the AC for possible icing after winter and defrost it.

6. The Refrigerant Level is Low

I remember mentioning refrigerant’s job, and that’s to cool your indoor air. If its level is lower, which could be the case if it leaks, your AC won’t turn on, and even if it does, it will go off repeatedly.

Overall, the refrigerant leaks following the cracking or rusting of the AC coil. Unfortunately, it’s not easy to inspect the refrigerant level unless you are an expert.

Fix

Ask an expert to help you check the refrigerant level and fix the source of the leakage.

7. The Compressor Might Have Failed

The compressor’s job is to convert the refrigerant or liquid coolant to gas. So, your AC won’t turn on if it’s faulty. You need it to turn on so the AC can start and run.

Fix

Replace the AC compressor if it won’t turn on. You can also ask for an HVAC expert’s help to determine if the compressor is faulty.

8. The Capacitor Could Be Dead

The capacitor’s job is to store the power necessary for starting and running the air conditioner. If it fails, which is likely to be the case when it ages, overheats, or overworks, it’s unable to store power for the air con. As a consequence, the AC is unable to start.

Fix

You need an expert to help you diagnose a dead capacitor and replace it.

9. The AC Unit Could Be Dead

Lastly, your AC unit won’t work because the whole unit has failed. That could be the case if it’s too old or needs too many repairs.

Fix

Consider getting another AC if you cannot fix the existing one or it has too many issues (repeat ones).

AC Won’t Turn On After Flipping Breaker

Given that a tripped breaker is one of the reasons why an AC won’t turn on, you expect the unit to power on when you flip it. That, however, may not be the case if there’s an underlying issue.

It could be that the source of the power failure is not just a tripped breaker but also one of these:

The AC might not be well plugged in
The power plug could be faulty
Loose or damaged wires
The thermal fuse might have blown up

AC Unit Not Turning On But Blowing Air

If your AC unit is not turning on but blowing air, there’s the chance it’s because of a tripped breaker. So, check the circuit breaker panel to reset the breaker if it’s flipped off.

If the breaker is okay, the problem could be the failed compressor or capacitor. The failure of either component may not prevent the fan from spinning, explaining why you feel like the AC is blowing air.

However, the AC won’t start. So, you need to replace the compressor or capacitor.

AC Unit Not Turning On After Power Outage

Once a power outage occurs, it can result in the circuit breaker’s tripping or the capacitor’s failure. So, start by checking the circuit breaker and reset it if it’s tripped.

If that’s not it, you may need to replace the capacitor as it could have burned out. But to be sure, talk to an HVAC expert to have them check the capacitor for fault.

AC Unit Not Turning On After Winter

The AC unit is likely to clog with ice and sometimes dirt during the winter because it’s dormant. Therefore, you may need to inspect it first to clean off the dirt and melt the accumulated ice.

If the AC won’t start after that, check the circuit breaker for tripping and reset it properly. You may also need to test the thermal fuse for continuity as it could have blown up and ensure the AC is well plugged in and turned on.

Outside AC Unit Not Turning On But Inside Is

As odd as it sounds, sometimes the outside AC won’t turn on, but the inside will. That could be the case if there’s power disruption following a flipped breaker or a blown-up fuse.

You may also need to check the setting to ensure you select ‘cool’ mode and turn on the on/off switch. If that’s not the case, the issue could be a clogged drain, broken compressor, or old air con.

Window AC Not Turning On

Overall, any of these issues could prevent your window AC from turning on:

Power failure due to a tripped breaker, loose wiring, blown-up fuse, or a faulty or loose cable
A malfunctioning thermostat
Ice buildup due to winter dormancy
Dirty air filter
Clogged condenser
Failed compressor or capacitor
The AC is too old to work

Closing Thought On Troubleshooting AC Unit Not Turning On

Now you have an exhaustive troubleshooting guide for an AC unit that’s not turning on. You can consider the nine issues whenever you cannot power your air conditioner. That’s important before you call an HVAC technician, saving you money and time.

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