This Is Why Your Outdoor AC Unit Stopped Working

Outdoor AC Unit

You set the thermostat to 75 degrees, but the display says it’s 77 inside. You stand under the supply vents to see if you feel any air. Nada. What’s going on?

To investigate further, you step outside to see whether your outdoor AC unit is operating at all. The fan isn’t spinning. It’s not even trying to come on. No clicking. No sound. No activity whatsoever.

Why did it stop working?

All sorts of problems can cause your outdoor unit to quit. Some of those problems are small. But others, well…

They might not be small problems at all. They might be big problems.

The good news? A little troubleshooting can go a long way, and you might not even need to call your HVAC company.

Here are a few common reasons your outdoor unit might stop working out of the blue.

1. Bad contactors

What would happen if your kitchen light switch burned up? You’d either have to cook in the dark or get a new switch.

Well, the contactor in your outdoor unit is like a switch that turns the AC on. If it goes bad – and they sometimes do! – your AC won’t run. You’ll have to hire an HVAC pro to replace the contactor.

2. Tripped pressure switch

If your AC is low on refrigerant (aka Freon) you might have a tripped pressure switch. The unit won’t turn on when you don’t have enough refrigerant, and an HVAC tech will need to analyze the system to see what’s going on.

You might just need a refrigerant recharge. Or, if you’ve got a leak, your tech might need to perform a leak search. In some cases, you’ll have to replace the system.

3. Burned up disconnect box

See that box mounted near the outdoor unit? That’s called the disconnect box. Sometimes, the connections in there come loose and burn up the box. It can also burn up if a breaker trips. Speaking of…

4. Bad breaker

Sometimes, circuit breakers get overloaded and go bad. You may have had this happen with less consequential circuit breakers – like the one that helps power your smoothie blender. But when it happens to the one powering your outdoor AC unit, it’s super inconvenient.

If you just have a tripped (but not inoperable) circuit breaker, that’s something you can fix. Flip it back into place and see if your outdoor unit turns on! It might.

If the system turns back on but the breaker trips again, don’t flip the switch a second time. There might be a direct short in the system, which is a safety hazard.

5. Disconnect switches

Homeowner troubleshooting opportunity: Check the disconnect switches at your indoor and outdoor HVAC units. They might have just been bumped. Maybe your kid threw a ball at the switch, or maybe your neighbor’s annoying cat hopped up and switched it off (not joking).

Anyway, if the disconnect switch is off, your outdoor unit won’t turn on. Just flip the switch, and you should be set!

6. Thermostat issues

Here’s another one homeowners can usually solve. Check your thermostat. If it’s not displaying anything, change out the batteries. Your AC might turn on right away!

If that doesn’t solve the problem, your thermostat might be broken. You can replace it yourself or call in your HVAC guy to look things over before making a purchase.

7. Low voltage wire problem

Some of the low voltage wires coming off of your outdoor unit might be semi-exposed depending on the installation. If one of them gets cut or disconnected (think careless landscapers), your outdoor unit won’t run. You’ll need to have the wire replaced or reconnected.

It’s best to hire a professional in this case unless you’re pretty handy with wires and know how to fix it without getting zapped.

8. Blown fuse

Boom! These things just blow up sometimes. It’s kind of like when the battery in your car goes bad. You have to replace it. If your outdoor unit isn’t working, it might be because the 3 or 5 amp fuse in the indoor unit went bad.

9. Bad capacitor

Same sort of thing, only no explosions or crackling noises. Capacitors tend to die slowly and quietly.

The capacitor is one of your outdoor unit’s starting components. It holds power and sends a jolt of it to your system to turn it on. These almost always go bad if you keep your system long enough. You’ll need to have them switched out for new ones.

10. Tripped float switch

Your indoor unit expels condensate as the air conditioner removes humidity from your home. If the condensate drain gets clogged, your drain pan will start filling with water. If you’ve got a working float switch, it will trip. The whole system, outdoor unit included, will stop working.

An HVAC pro will need to inspect the system to see why the condensate line was clogging.

Most of the time, even the trickier issues can be fixed quickly.

You probably won’t have to replace your air conditioner when any of this stuff happens. For your HVAC company, these are common and straightforward fixes.

And if you’re in the habit of getting your AC inspected each year, you’re a lot less prone to these issues than your neighbor who just hopes and prays everything is working ok. Everything always is working ok… until it’s not.

If troubleshooting gets you nowhere and things are starting to heat up, you know who to call.