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Why Won’t My Air Conditioner Turn On?

 |  Air Conditioning, Blog

Here in Arizona, air conditioning isn’t a luxury. When temperatures soar past the 100-degree mark, you need it to keep family and pets safe. That’s why you feel such a sense of panic when you stand in front of the thermostat wondering why your AC won’t turn on.

When your air conditioner refuses to start, take a deep breath. There are numerous reasons this happens that don’t require completely replacing your unit or paying for an expensive repair. Before calling in a service tech, answer a couple of questions first.

  1. Does the unit not run at all?
  2. Or, does it run but not cool the air?
  3. Is it the outside unit that doesn’t turn on, your inside air handler, or both?

This helps determine where the issue is.

Next, work your way through the suggestions below. If you do each of these and your air conditioner still won’t run properly, it’s time to either repair or replace the unit. Unfortunately, most air conditioners are designed only to last between 10 and 20 years. If your air conditioner falls within that lifespan, it might be time to replace it rather than waste money to repeatedly repair your air conditioning system.

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Common Reasons Air Conditioners Don’t Turn On

Are the Batteries in Your Thermostat Dead?

Simply put, if the batteries in your thermostat are dead, the AC won’t run. Luckily, this is an incredibly easy fix. It’s also one of the most common reasons air conditioners stop running but is one of the last things most people think to check.

Pull back the thermostat cover gently to reveal the batteries. You should also see a tiny circuit board. Simply pull out the batteries and replace them with a new pair. Then, return the plastic over and switch your thermostat to either Auto or On. If you hear the sweet, sweet sound of that cold air blowing, congratulations! Just remember to replace the batteries yearly, say when you pay your taxes or perform the same chore with your smoke detectors.

Do You Have a Dirty Filter?

A dirty filter may cause an air conditioner to freeze up. When this happens, the unit may continue to run but not actually cool the air. It may also cause the unit to stop turning on.

To determine whether a dirty filter is the cause of your issue, touch the handler (it may be on the roof or possibly inside). It shouldn’t feel cold. If it does, or if you see frost or ice, then your problem is most likely a dirty air filter.

Turn off your air conditioner, at least the cooling function. This allows the unit to thaw. If necessary, you may allow the fan to blow. Then, go to the thermostat and switch it from Auto to Fan. Next, turn the system from Cool to Off. Replace the dirty filter with a new one. Once the handler returns to a normal temperature, you can turn the AC back on.

Guard against this issue by replacing your filters regularly. During the summer, this means every-other-month at least (and we recommend monthly). During the months your system gets little use, you can change every two to three months. This may not match the advice from your manufacturer, but Arizona is extremely dusty. We need to replace our filters more frequently in the Valley of the Sun.

Isley’s Home Service provides regular HVAC maintenance checks. Learn more about the options we have available.

HVAC Maintenance Agreement

Maintaining Good Air Flow in Your Home by Changing Your Dirty AC Filter:

A dirty condenser or evaporator may also cause the system to stop working properly. Unfortunately, this typically requires the help of a professional.

Are You Out of Coolant?

If you’re either low on or out of coolant, this keeps your air conditioner from cooling the air efficiently. Of course, refrigerant is a gas and it does seep out over time. That’s one of the reasons we recommend an annual AC service, so coolant can be topped off. Unfortunately, while a simple repair, adding coolant is a job for a pro.

You may also be low on coolant due to a leak in your system. If your unit continually runs low on refrigerant, your AC tech may choose a dye-colored coolant to help pinpoint the source of the leak.

A Bad AC Motor

When the air conditioner motor goes bad the unit stops working. Call a professional to examine the wiring leading to and from the condenser unit. If the motor proves to be bad, then you have a decision to make: Do you replace the motor or repair it?

When an air conditioner repair costs more than half the original cost of the unit, we recommend replacing it. History shows your problems are only beginning. You also get a more energy-efficient unit, saving you money in the long run.

Proper HVAC maintenance and yearly checks of your home’s HVAC system will preclude many problems associated with air condition repair, and could even extend the life of your unit. Give us a call if you have questions we haven’t answered our website or just want more information. We’re always happy to help.

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Additional Resources

How to Take Care of Your AC Unit

In the following video, Isley’s ac technician, Ernest Perez, demonstrates some simple air conditioning unit maintenance tips to ensure your ac is running at its optimal level and help prevent future costly repairs.

Ask Johnny D

Ask Johnny DIf you have any additional AC repair or HVAC questions, we’re always available and will reply ASAP. I’ve been in the business since the 1980s, and my team and I have a combined 200+ years of experience in heating, cooling, plumbing, and other home services.



Common AC Issues Infographic:

Common Air Conditioner Issues Infographic