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How to Fix the Most Common Air Conditioning Repairs Yourself

Our experts explain how to repair the most common causes of central air conditioning service failures.

DIY Air Conditioning Service Repair

If your central air conditioning system stops working during a brutal summer heat wave, you could be waiting days, if not weeks, for an appointment with a repair technician to fix it, and it’s probably going to cost a few hundred dollars. However, if you’re comfortable working around electricity and willing to spend less than $100 on parts, you can probably repair your air conditioner yourself in about two hours.

We talked to local HVAC repair technicians to get their best do-it-yourself AC fan repair and maintenance tips. These tips will help you with the most common “low cooling” and “no cooling” problems.

You’ll need a few basic tools: a multimeter, a voltage detector, an assortment of insulated screwdrivers, and a socket set.

If these AC repairs don’t work, at least you’ve covered the most common failures, and your service guy can concentrate on finding the more elusive problem. Plus, with the new parts, you’ll likely add years of breakdown-free air conditioning. Here’s how to start.

Home repair AC

Why Is My Air Conditioner Not Cooling the House?

Set your thermostat to AC mode and lower the temperature setting. If the furnace fan kicks in, the problem isn’t in the furnace. If the fan doesn’t run, try resetting the furnace circuit breaker. If the fan still won’t start, call a pro — the fixes shown here won’t work.

Next, check the outside condensing unit. The compressor (which sounds like a refrigerator) and fan should be running. If not, follow the troubleshooting and repair procedures shown here.

Caution: Turn Off the Power

Turn off the A/C and furnace breakers in the main electrical panel before pulling the outdoor disconnect or removing the condensing unit’s access panel. Then use a voltage tester on the wires coming into the contactor to make sure the power is really off.

AC Doesn’t Work? Buy Parts

The AC contactor (relay) and start/run capacitor(s) fail most often and are inexpensive. So it’s a safe bet to buy and install those parts right away, especially if your air conditioning service unit is older than five years. The condenser fan motor can also fail, but it runs about $150 — hold off buying that unless you’re sure that’s the culprit.

To buy replacement parts, find the nameplate on the condensing unit (not your furnace). Jot down the make, model, and serial number (or take a photo). Get the parts at an appliance store, furnace dealer, or online.

the Anatomy of a Central Home Air Conditioner

Central home air conditioner service systems consist of two major components: a condenser that sits outside your house and the evaporator coil (often referred to as an A-coil) that sits in the plenum of your furnace or air handler. The refrigerant in the A-coil picks up the heat from your home and moves it to the outdoor condensing unit.

AC repairs - DIY

The condensing unit fan blows outside air through the condensing coil to remove the heat. The condensing unit houses the three parts replaceable by a DIYer: the AC contactor, the start/run capacitor(s), and the condenser fan motor. The condensing unit also houses the compressor, but only a pro can replace that. The A-coil has no parts that can be serviced by a DIYer.

Shut Off the Power

Open the electrical box next to the condensing unit and pull the disconnect block straight out. Check inside the box with a voltage sniffer to make sure the power is really off.


Fixing common air conditioning issues yourself can save time and money, especially during peak seasons when professional services are in high demand. By understanding the basic components and common failures, and having the right tools on hand, you can address many issues on your own. Remember to always prioritize safety by turning off power before starting any repairs. If the problem persists or is beyond your comfort level, don't hesitate to call a professional technician to ensure your system is running efficiently and safely.


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