Why Won’t My Home’s A/C Turn On?

It’s frustrating when your A/C won’t turn on, especially when it’s hot and you need cool air the most.

We feel your frustration. But here’s some good news: we’ve helped many homeowners fix an A/C that won’t turn on, so we know what’s causing the problem.

Here are 4 common problems that keep your A/C from turning on:

1. Dirty air filters
2. Malfunctioning thermostat
3. Circuit breaker issues
4. Clogged condensate drain line

In this article, we’ll discuss each of these common AC problems and share DIY repairs you can try before calling a professional for AC repair.

4 common A/C problems with easy DIY repairs

#1: Dirty air filters

If your filter looks like the one on the right, it’s time to replace it.

Dirty air filters block air from returning to the air conditioner, which causes pressure to drop and ice to form on the evaporator coil.

When this happens, a low-pressure switch trips and shuts down your A/C’s compressor (the heart of your system) to protect your system from further damage.

DIY solution: Check your air filter and change it if it’s dirty. In the heat of the summer, when you’re putting a lot of demand on your A/C, consider changing your filter once every month.

#2: Malfunctioning thermostat

Your thermostat is the brain of your cooling system. If it’s set to the wrong setting, or it’s low on batteries, your A/C won’t turn on.

DIY solution: Try these 2 steps:

Make sure your thermostat is set to “cool” and not “heat” (it won’t turn on if it’s set to heat)

Replace your thermostat’s batteries

If you’ve tried those 2 steps and your A/C still isn’t on, contact a professional.

#3: Circuit breaker issues

Circuit breakers on an electrical panel.

Your air conditioner requires electricity, so if your circuit breaker is tripped or broken, then your A/C won’t power on.

DIY solution: Find your electrical panel (see image above) and look for tripped breakers. Turn them “off” and then “on” again. If the breaker trips again immediately or after a few minutes, don’t reset the breaker; call a technician for help. You most likely have a short or grounded circuit which a professional will need to fix.

#4: Clogged condensate drain line

An outside condensate drain line.

Your condensate drain line carries the condensation that forms inside your A/C outside your home. If the drain line is clogged, water will start to overflow, and your drain float switch will shut down your A/C.

DIY solution:

1. Find a wet/dry vacuum
2. Locate the main condensate drain line (pictured above) outside your home
3. Using the vacuum hose, suck out any debris or obstructions for about 3 minutes

If that didn’t fix the problem, there may be other issues causing your A/C to break down...

More reasons your A/C isn’t turning on (and why a professional need to help)

If you tried those DIY repairs and your A/C still isn’t turning on, the problem may be something a professional need to fix. These types of problems include:

• Low refrigerant levels: If your A/C has insufficient refrigerant, your low-pressure switch will trip, which will shut down your system to prevent damage. You’ll always want a professional technician to check and change refrigerant fluids.
• Dirty condenser: If dirt builds up around your system’s condenser, it could cause your system to break down and not start up again. An air conditioning expert can clean your condenser.
• Wiring problems: If your circuit breaker keeps tripping, that could be a sign of faulty wires or a blown A/C fuse. Only a trained and certified technician should handle problems related to wiring and electricity.
• Busted contactor or capacitor: Your A/C’s contactor and capacitor help power the fan and compressor when your system calls for cold air. If one or both of these components are busted on your A/C, you may still hear your A/C’s fan turn on, but you won’t feel any cold air. A professional can replace or repair a broken contactor or capacitor.
• Icy buildup: There are many A/C problems that create icy buildup in your system, but most of them require professional repairs.

Related article: Why Is Ice Building on My A/C Unit's Pipes?

• Faulty motors: In most cases, your air conditioner will shut down if the motor is faulty. Your A/C contractor can help you decide if they can repair the motor or if you need to replace it.
• Broken compressor: The compressor is the heart of your air conditioning system. If it is broken or malfunctioning, your entire system could shut down. A professional can inspect your compressor and repair any compressor-related issues.