DIY Air Conditioner Repair
Overview: Central air conditioner failures and solutions
When a central A/C unit fails during a heat spell, you may have to wait days for a technician to show up, and you’ll probably pay at least several hundred for the repair. But if you’re comfortable working around electricity and are willing to spend about $50 on parts, you can probably repair you air conditioner yourself in about two hours and save about $225 on parts markup and labor.
We talked to local HVAC technicians to get their best do-it-yourself A/C repair and maintenance tips. These tips will help you with the most common “low cooling” and “no cooling” problems. You’ll need an inexpensive multimeter, a voltage sniffer, an assortment of screwdrivers and a socket set.
If these fixes 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.
Make sure the problem isn’t the furnace
Set your thermostat to A/C 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.
The contactor (relay) and start/run capacitor(s) (see illustration below) fail most often and are inexpensive. So it’s a safe bet to buy and install those parts right away, especially if your A/C 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.
Anatomy of a Central Air Conditioner
Central A/C systems consist of two major components: a condensing unit 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. 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 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.
Central air conditioner components