13 Reasons Your AC Is Not Turning on & How to Fix Them

You expect your air conditioner to work perfectly fine every time you turn it on; after all, it is your comfort companion in every season.

But sometimes, your HVAC unit can leave your side and refuse to turn on. If you’re facing a similar situation, then don’t fret! It might be something that can be easily fixed as a DIY solution or, in some cases, with a phone call to a professional.

From maintenance issues to your unit getting old, there can be various reasons; we have compiled an extensive list to help you figure out why your AC is not turning on and how to troubleshoot the cause.

1. Thermostat Malfunctioning

Your air conditioner has stopped working all of a sudden. You panic and start calling different air conditioner experts.

But stop for a second. Have you checked your thermostat?

Thermostat malfunctioning can have an impact on your air conditioner’s performance.

First, check if the display of your thermostat is lit. If it’s off, it cannot signal the AC to turn on. Second, check the batteries of your thermostat if you have a battery-operated thermostat.

If the batteries are fine, then check the working of your thermostat. Set it to a cool setting, keeping it 5-6 degrees lower than the indoor temperature. After a few minutes, place your hands in front of the AC vane to feel the cold air. If it has turned on, then voila, you have solved the issue!

But if your AC still has not turned on, turn off your thermostat and take off the cover to check its components. Look for debris or corrosion build. Also, look for blown fuses; sometimes, they are the culprit. You can clean out the debris yourself with a soft brush, but you would have to contact a professional for corrosion issues.

Further, check if there are any loose screws or wires inside the thermostat. You would have to refer to the user manual for correct wiring schematics.

2. Low on Refrigerant

One of the reasons your AC is not turning on could be due to a refrigerant shortage.

A refrigerant is a cooling fluid residing in an AC’s coils. It is mainly responsible for providing the much-desired cool air from your AC or hot air in case of a heat pump.

The refrigerant shortage is not due to your air conditioner using up the fluid. Leakage is a likely culprit in this situation. The cracks may build up over time in the AC coil leading to leakage. Further, not taking out time for regular maintenance can lead to corrosion in the long run.

You cannot do much on your own in this situation as it is not just about filling the refrigerant; the levels must match exactly with the levels specified by your AC’s manufacture. You would have to contact a professional to check the refrigerant levels and figure out the reason for leakage.

You can avoid this problem in the future by ensuring regular maintenance of your air conditioner.

3. Clogged Air Filters

Do you remember the last time you cleaned the air filters of your air conditioner?

If your answer is no, then it’s a big problem as your AC may not be able to work properly due to dirty, clogged up filters. No matter what type of air conditioner you have, cleaning the filters is a must!

The job of the filters is to ensure proper air circulation. If they are filled with debris, then airflow is pretty much blocked. In this case, your system has to work harder to cool your home, and over a period of time, it can stop working.

Dirty air filters can also freeze your outdoor AC unit, which hinders your system’s working and, in some cases, is the reason why your AC is not turning on.

Weird, but it happens.

The indoor unit of your AC has the evaporator coil, and the outdoor unit contains the compressor. The refrigerant line is between these two components. When the airflow is restricted, warm air from your house does not reach the refrigerant. The refrigerant then becomes so cold that any moisture on the coils freeze.

It’s scary, but you don’t need to panic. You can call a professional to deal with the situation, or you can clean the filters yourself. The ice on the coils will melt, so make sure to collect the water properly. After cleaning, let the filters dry completely before turning on the air conditioner.

We recommend using a smart thermostat if you have a ducted system or a smart AC controller for a ductless mini-split unit to monitor your AC’s air filter cleanliness level. Continuous monitoring can help avoid the issue of clogged filters in the future.

4. Your AC’s Capacitor Has Died

If your HVAC unit has trouble starting off if it is starting and stopping abruptly, or if you hear some clicking noises from the outdoor AC unit, chances are that your AC’s capacitor has died down.

The capacitor is an integral part of your HVAC system. It is connected to the motor’s circuit and gives the motor an initial push to start running. The capacitor disconnects from the circuit once the motor reaches a specific speed.

There are two types of capacitors:

• The start capacitor provides voltage to get the motor started
• The run capacitor provides energy to keep them running

What Causes the Capacitor to Fail?

Your AC’s capacitor is sensitive to heat. Overheating can be caused by your AC working hard to achieve the desired temperature or due to its exposure to the sun. If your outside unit is installed on the roof, it will likely become a victim of overheating on hot summer days.

During extreme cold or hot days, avoid setting the highest/lowest temperature on your thermostat as it can also cause the unit to work harder, resulting in an overheated capacitor.

Power outages and power fluctuations can also significantly damage the capacitor. To prevent damage from power fluctuations, consider installing a surge protector.

Furthermore, old age can cause it to die down as the capacitor’s ability to release energy decreases over the years.

As far as the age is concerned, regular maintenance will help you detect capacitor problems early. The solution is quite simple – have an electrician replace the capacitor.

Note: Never try to replace the capacitor yourself as there is an electrical charge stored in it; there is a risk of severe electric shock. Never try to run your AC on a bad capacitor as it can burn the motor attached to it, and replacing the motor can be quite costly.

5. Dormancy Issue

If you cannot figure out why your AC is not working, check the fan. If the AC fan is not turning on, it could be a dormancy issue. Or if your cooling system was lying dormant in winters and you have switched it on after some time, then fans may find it hard to start rotating again because of the dirt buildup.

Call an HVAC expert; they will know how to start the fans manually. The problem shouldn’t persist once the fans are out of dormancy.

6. AC Not Turning On? – Check the Switch

It’s the most obvious reason, but people overlook it all the time.

Just like any other electric appliance, your AC also has an ON/OFF switch. You will find it near to where your system is installed.

You may not have turned it off, but someone in your home could have done it. So, whenever your system refuses to turn on, do check the switch before you do anything else. The solution is simple, turn on the switch, and you would be feeling the pleasant breeze of air blowing in no time!

7. Uncleaned Condenser

Is your external AC unit not turning on?

The external or outside unit of your AC is called a condenser. Its job is to release the heat collected by the inside unit to the external environment.

Without regular maintenance, the condenser can get really dirty over time. It will have to work harder to disperse the heat as dirt acts as an insulator. The condenser will start drawing too much current, tripping the circuit breaker, and your AC won’t turn on.

If you think that the solution would be easy since you can clean the condenser yourself, well, unfortunately, it’s too late for that now. Once it is non-functional due to dirt, it may be time for a professional clean-up. Improper cleaning can damage the compressor coil’s fins, which is way worse than the dirt on the coils.

You can, however, as a maintenance routine, keep cleaning your condenser regularly yourself to prevent any major issues.

8. Tripped Circuit Breaker

If you have a tripped circuit breaker, your AC won’t turn on.

So, whenever your AC unit is not turning on, do check the circuit breaker.

A circuit breaker is a safety tool that turns the power off in case of heavy voltage.  It may be due to using high voltage appliances or power surges in the electricity grid.

All you’ve to do is find the air conditioner circuit breaker and turn it off completely. Then wait for a few minutes before turning it on.

Safety tip: If it keeps tripping, do not try to turn it on as it indicates a high voltage and can cause an electric fire. It is a problem that needs to be fixed by an expert.

9. Is Your AC Not Turning On Or Has It Run Its Course?

Your AC has stopped running, and you are wondering what could be the reason. If it has been your comfort companion for quite a long time, maybe it has reached the end of its lifespan.

But how can you actually tell that it’s time to say goodbye to your AC?

Following are some signs indication why your AC is not turning on: 

• You notice a significant decrease in AC’s airflow. The decreased airflow can be due to dirty filters, but if cleaning the filters does not work, your AC has aged and needs replacing.
• Your AC requires repair services every now and then, which could give a clue if your AC has problems related to its lifespan.
• Your bills are increasing at an abnormal rate. Near the end of life, the AC becomes sluggish and overworks to maintain the desired temperature, leading to a surge in bills. You can go for an energy audit to see if it is really your air conditioner causing the bills to increase.
• The inside unit of your AC is leaking excessively. It may be due to a refrigerant leak, but even if the issue does not get resolved, it’s time for the unit to go.
• If your AC is making weird loud noises such as grinding, screeching, rattling, it’s time to replace it as it signals a serious problem.
• Your air conditioner smells bad. It could be due to molds growing inside your unit or due to dirty filters, but if the smell does not go away, consider replacing it.

If you are experiencing some of the above-mentioned signs and your AC is more than a decade old, you surely need a new unit. But do not take the decision on your own, have a professional thoroughly check your unit before going for a replacement.

Also, read these six ways to extend the average life of your AC.

10. Clogged Drain Pan

Your air conditioner unit not only cools or heats your house but also removes moisture from the air. So, where does that moisture go?

It is collected in the drain pan, located underneath the indoor unit evaporator coils, then flows into the condensate drain line, which is directed outside.

Without regular cleaning, especially in areas with high humidity, the drain pan can become clogged. The drain pan has a secondary drain to prevent the pan from clogging. But if both of them are full, this triggers the float switch, which turns the AC off. It is a safety mechanism that prevents excessive leakage in your house and prevents damages to the unit. But even then, the water leak from the clogged pan can damage your walls, ceilings, and furnishings.

So, your AC is not going to turn on until the pan is cleaned and the float switch is turned down.

You can use a wet/dry vacuum to suction the blockage out, but it is going to be really messy so if you don’t want to see all that gunk, better call an HVAC technician.

Make sure never to have this episode and do regular maintenance. You can use a wet/dry vacuum during the routine cleaning; we hope it won’t be this messy!

11. Damaged Motor

If you hear grinding noise when you turn on the AC, it is not a good sign as it may indicate malfunctioning motor blades.

Motors are sealed to prevent any contact with the outside air, water, or debris. Over time, due to old age or lack of maintenance, the seal can come off, and the oil which was sealed within the motor needed for lubrication seeps out. Without oil, the motor can wear out and can stop working entirely after some time. The outside unit cannot dissipate heat if the motor is faulty.

One question that arises; should you repair the motor or replace your air conditioner?

Here’s a tip that will make it easy to decide; if it costs half the amount of the original price, then consider replacing your system. The price range is $150 to $750 for a new motor.

Contact an HVAC specialist for a thorough inspection.

12. Faulty Power Cord or Outlet

Sometimes the issue is not severe; it’s just that you are anticipating the worst. So, examine simple things that are right in front of you; check the power cord, for instance.

The power cord can become frayed and wear down if your unit was stored for a season. Power outages can also damage the cord.

Unplug the cord for proper examination. If it shows signs of damage, you would have to replace it.

Or maybe it is not the cord, but the outlet was plugged in. You can check if the outlet is working fine by plugging in other appliances. If none of them work, you know what’s causing the issue.

Call an electrician to repair or replace the outlet, depending on the damage.

Safety tip: You should never attempt to repair the cord or power outlet yourself. There is a risk of getting an electric shock if you don’t turn off the power supply. Just turning the switch off won’t do; you have to turn the power off from the main power box.

Related: Home AC Blowing Warm Air? 12 Possible Causes and Their Solutions

13.  Your AC Is Not the Right Size

Did you take into account the size of an air conditioner when buying it? Well, it is a mistake that is continuously overlooked but can have a great impact on the performance of the HVAC system.

The air conditioner that is not the right size will have to work harder and, at one point, will break down completely.

When your AC is larger than required, it will keep turning on and off quickly, increasing wear and tear. Further, it won’t remove the excess humidity as it does not stay on for a sufficient time.

On the other hand, a small unit will have to run for a long time to cool/warm the house, which may cause overheating of the capacitor.

An HVAC system that is not the right size can also wreak havoc on your bills.

Unfortunately, the only solution is to replace the unit.

Some parameters determine what size you require, such as the area of your house, climate, number of windows, and insulation level. You will have to go for a professional evaluation to find out the perfect size of air conditioner for your home.

There is also an equation that roughly estimates the right size of AC. 

(Square footage of your home x 25/ 12000) – 0.5 = Required AC size

Let’s say your area is 1000 square feet.

(1000×25/12000) – 0.5= 1.5

You require a 1.5-ton AC.

If you figured out why your AC was not turning on and managed to find the solution on your own, congratulations! But even then, we recommend that you contact a professional for a complete inspection to avoid similar problems in the future.

By having an HVAC expert perform annual inspections and staying on top of the maintenance routine, you can avoid any potential AC outages in the future.