That dreaded moment: It’s hot, you switch the thermostat on, and nothing happens – the AC unit won’t turn on. Eventually it happens to every homeowner and I’m no exception. The only difference between myself and most homeowners is, I’m the guy who must fix it when it’s mine! This article covers a few of the possible problems (and solutions) when your AC unit won’t turn on.
10 Reasons Your AC Won’t Turn On
My Outside AC Unit Won’t Turn On
It may take a little while before you even notice your AC unit outside isn’t working.
Has this ever happened to you? You lower the temperature as usual, you hear the inside fan motor running, and keep doing what you were doing. After a while you realize it’s not getting cooler in your house … in fact, it’s getting warmer! You walk back to your thermostat, and it’s gone up a degree or two, but it says the AC is on. You walk outside to look at the condenser (outdoor AC unit) and find it’s not running. Ugh!
5 Reasons Your Outside AC Unit Won’t Turn On
There’s a multitude of reasons why your outside AC unit won’t turn on, here’s 5 of the most common.
- Bad Condenser Fan Motor The condenser fan motor expels the heat removed from your home outside. It does this by removing heat from the refrigerant flowing through the outdoor coil. It also assists in keeping the compressor cool. Without being able to remove heat, the compressor will overheat and prevent the condenser unit from running.
- Faulty Capacitor A capacitor aka voltage absorber aids the connected component in running and not overamping. Both your condenser fan motor and/or compressor may require a capacitor. Some new compressors do not require a capacitor due to the inverter technology they use. If your capacitor fails or is faulty, it’s likely your AC unit won’t turn on. It’s also not uncommon for a faulty capacitor to cause it’s connected component damage as well.
- Bad or Damaged Compressor The compressor is to the AC unit what the heart is to the body. A bad or faulty compressor is never good news. So, if you’re technician tells you it’s a bad capacitor or fan motor, count your blessings, you just saved money!
- Broken PCB (Printed Circuit Board) Most modern AC units utilize electronic circuit boards that control the mechanical components. Every year, these boards get bigger and more complex and unfortunately – are usually unrepairable. In the old days, we could often take these boards back to our shops and repair them. However, today we live in a “disposable” world. Even a small problem on a PCB can be the reason your AC unit won’t turn on.
- Low Refrigerant The compressor is to the AC what the heart is to the body, the refrigerant is the blood. If your system runs low on refrigerant, the low-pressure switch is the reason your AC unit won’t turn on. The low-pressure switch is designed to protect the compressor from running without refrigerant flowing.
Pro-Tip: Your air conditioning system is a “sealed system” which should never lose refrigerant. If your AC unit won’t turn on because of low refrigerant, it means you have a refrigerant leak. Much like a cars oil leak, your technician will need to find the leak, repair it, and then add refrigerant. If not, you will continually be repairing the system and buying more refrigerant. The worse the leak, the more often you’ll need more refrigerant.
Did You Know?
It’s not Freon! Freon was Dupont’s brand name for R-22 refrigerant. There are very few R-22 residential units still in use in the Phoenix area. In fact, the units they were replaced with used R-410a, which is being phased out in 2025 by the EPA.
5 Reasons Your Inside AC Unit Won’t Turn On
We talked about the outside air conditioner not turning on, let’s turn our attention to the inside unit now. Most of us have what’s known as a split air conditioner or split heat pump. A split air conditioner has an outdoor AC unit connected via pipes to an indoor coil & furnace. A split heat pump has an outdoor heat pump which provides both heating and cooling. That unit is connected to an indoor air handler with a coil inside it.
There are fewer components in the indoor unit than the condenser. That said, there are a few that if broken, would explain why your inside AC unit won’t turn on. Here’s the top 5 reasons your inside AC won’t turn on:
- Bad Indoor Fan Motor This motor circulates conditioned air through the return, across the evaporative coil, and into the ductwork. If your indoor AC unit won’t turn on and you don’t feel air movement, the indoor fan may be faulty.
- Faulty Capacitor Many (not all) blower motors also utilize a capacitor the same way the outdoor fan and compressor do. A failed or weak capacitor could cause your AC indoor unit to not run.
- Dirty Coils / Filters Dirty evaporator coils and/or plugged air filters will restrict airflow across the coil. If left unchecked season after season, this dirt will restrict air to the point the coil freezes over. Lack of maintenance, pet hair, dust, and dander buildup can all lead to plugged coils and further damage equipment components.
- Circuit Board Failure Again, just as your outdoor unit uses PCBs, so do many indoor units. Circuit board failures are not uncommon as they often must combat their two biggest “killers,” heat and dust.
- Refrigerant Leaks both indoor and outdoor coils can develop refrigerant leaks. Remember, the indoor and outdoor coils are connected via refrigerant lines (which themselves have the potential to develop a leak). No matter where the leak is located, inside or outside, low refrigerant can explain the reason your AC won’t turn on.
Packaged Units aka Rooftop Units
Packaged units have all the same components as split systems. The main difference being rather than having a separate condenser and air handler, they’re all together in the same “package”. That said, the same 10 reasons we discussed above all apply to a package unit as well.
Now You’re a Pro!
You know more about your HVAC System now than you did a few minutes ago, you’re ready to repair it.
Okay, maybe not, I was just jesting! In fact, as expensive as HVAC equipment is nowadays, I highly recommend leaving repairs to a pro. In my 36-years as an HVAC technician and installer, I’ve seen DIY-ers cost themselves a lot of money DIY-ing. I once visited a home where the owner attempted to clean his own coils … sounds easy right? Well, in this case he ruined the coil, and it was no longer made – the entire system needed to be replaced! His wife took over from there and I never saw him again … I hope he’s okay.
Just Call Magic Touch for Air Conditioner Repair Near Phoenix
I write these articles for homeowners so you can be better informed about your homes HVAC, fireplace, energy use, etc. When the time comes that you need a service company you can trust, I hope you’ll use Magic Touch.
I’m so confident in my team, I back everything we do up with a lifetime workmanship guarantee and a 5-Star service guarantee. There’s a reason we have over 3,000 glowing customer reviews online and we look forward to you writing the next great review! REQUEST AN APPOINTMENT
