There’s nothing worse than coming home on a late summer evening to find your house is hot and stuffy—the air conditioning shut off while you were at work. Before the frustration sets in, follow this guide to walk through these DIY air conditioner troubleshooting tactics that address common causes of A/C issues.

If the A/C unit won’t turn on:

Check whether it is receiving power. A tripped breaker or a blown fuse could be preventing the flow of electricity to the unit. Reset the breaker or replace the fuse.
Make sure the thermostat is switched on and set to COOL.
Replace the batteries in the thermostat. While you have the cover off, check that all the wires are attached to the correct terminals. Replace the cover and then wait a few minutes before switching it back on.
If you have a digital multi meter, use it to check the compressor’s capacitor and wires. The capacitor operates both the A/C condenser and the fan, so if the capacitor has failed the unit will not be able to run.

If the A/C unit is on, but not cooling:

First make sure that nothing is impeding air flow anywhere in the system—check whether the filter needs replacing or whether there’s something blocking one of the registers.
Check the indoor air handler for dirty filters, icy coils, or blockage in the condensate drain. Frozen coils should melt on their own within an hour or two. A clogged condensate drain needs to be cleared by hand.
Check the outdoor compressor—give it a thorough clean and make sure it’s working. If the fan isn’t spinning, flip the reset switch or use a screwdriver to give the blades a boost to get going. If that doesn’t work, hire a professional to check the coolant.

If the A/C isn’t blowing air:

Check the indoor evaporator coil. A dirty or frozen coil will cause reduced air flow.
If the blower motor runs but no air blows out, the belt connecting the motor and the blower is probably broken. It’s an easy repair if you have a little know-how.
If the blower motor makes noise but doesn’t move, it probably needs to be replaced.

If the A/C is leaking water:

Make sure the condensate pump is connected to electricity.
If the pump appears to be clogged, use a wet-dry vacuum to suck the water out. If you don’t have a wet-dry vacuum, you may find it easier to replace it.
If the pump is running but doesn’t empty the drain, the check valve may be stuck. Check for blockage or build up the condensation drain tube—if the tube is clogged, replace it.

If you’ve tried these troubleshooting tactics and still can’t get your air conditioner to work, it’s time to call in the professionals. No A/C or a leaking unit qualify as an emergency, and we’ll provide immediate service to help you, 24/7.