DIY air conditioning repair

DIY air conditioning repair

Broken air conditioner? Empty wallet? You can do this, and we can help.

Key tips to remember

  • Study your system to learn how it works
  • Cut the power before troubleshooting
  • A good cleaning just might fix it
  • Check all the common problem areas
  • Know when to call in a pro


Having trouble with your air conditioner right before the weather heats up? It’s time to consider DIY air-conditioning repair and take action before things get hot, humid, sticky and uncomfortable inside your home. Paying a professional for air-conditioning repair services is the fastest and easiest way to get it done, but it can get expensive. If you’re not afraid to get in there and wrench around, and you’re comfortable working with electricity, then air-conditioner troubleshooting and do-it-yourself central air-conditioner repair are not entirely out of reach — with a little help from a handy article like this. If you already have tools, $50 to $100 in parts and two or three hours of your time can save you hundreds on what you might have to pay a pro.

How do you fix a broken air conditioner? Well, there are several possibilities, and we’ll do our best to cover most of the more straightforward fixes for low-cooling or no-cooling issues, using tried-and-true DIY home A/C repair techniques. First off, you might want to grab a few tools, like a voltage tester, a socket set, an adjustable wrench, a cordless drill, a nut driver, insulated screwdrivers, a multimeter and needle-nose pliers. 

As far as materials, you may need a new capacitor or two, some fuses, a can of compressed air, a contactor and maybe a condenser fan motor. Please read the full article before attempting to service your air conditioner, and don’t hesitate to take photos, draw diagrams and take notes as you go. When you take things apart, especially for the first time, tracing your steps in this way can make things easier.

Learn what’s what

A central HVAC unit has two main components. There’s the condensing unit, which is that machine sitting outside your home. It houses a fan motor, a contactor (relay) and a start/run capacitor (one or more). Each of these first two parts is DIY-replaceable on the cheap; you can do the fan relatively easily as well, but a new one goes for around $150. Once you’re sure of the ones you need, replacement parts aren’t tough to find, and they usually have make, model and serial numbers. The condenser also contains a compressor, but a pro best handles that. 

The second main central HVAC component is the evaporator coil (or A-coil, which is sort of A-shaped), which resides inside your air handler or within the plenum of your furnace, where the air circulates. A-coil parts are also best left to the professionals when your A/C unit requires service. The A-coil contains refrigerant, such as Freon, which grabs heat from inside and moves it to the outside condenser. The condenser blows air through its coil with a fan, removing heat.

Power down first

The last thing you need is a shock to the system (just ask Billy Idol). The first step of DIY air-conditioning repair is to always — always — make sure you turn off the power before you try any troubleshooting. Electrocution will quickly eclipse any DIY savings from fixing things yourself. 

Begin by going to your main breaker box or electrical panel, where you can find the breakers for your HVAC and furnace. If you have trouble tripping breakers, you may need to call a pro, but first, turn these two breakers on and off. Sometimes all they need is a reset. Break out your voltage meter to test the wires going into the contactor. This should confirm that the power is off. Next, open the condenser’s electrical box. Pull out the disconnect block. Double-check inside the box with your voltage meter to confirm that the power is off.

Panel check

Time to check your unit’s electrical panel. The conduit sticking out from the side of your home runs directly into the electrical access panel on your condenser unit. Again, make sure the power is off. Then unscrew the panel and look for damages or gunk buildup. If you’re still comfortable working with electricity, discharge the capacitor and proceed to repair or replace any broken or chewed wires, insulation or connectors.

Capacitor replacement

Each unit has at least a single capacitor, which stores electricity and releases it to help the compressor and condenser motors with the extra power they need upon start-up, while evening out the voltage flow to protect both motors. Capacitors can break down gradually or all at once. Because they’re pretty cheap, it doesn’t hurt to replace them during routine maintenance, especially if it’s been five or more years. After discharging the old capacitor, use your pliers to move one wire at a time to the new one, snapping each into its corresponding tab, making sure it’s tightly in place. After you transfer all the wires, ensure the new capacitor is secure.

Contactor replacement

The contactor is basically just a relay switch. It takes low-voltage power from the thermostat to 220-volt high-amperage power for the compressor and condenser. Like capacitors, contactors tend to wear out and cause system failures. If you do one of those every-five-years services, it’s worth replacing this $25 part, even if your contactor still works. First, unscrew the contactor before removing its wires, then attach the wires to the new contactor. Finally, secure the newly connected contactor into your condenser.

Start cleaning

Sometimes, your condenser unit just needs a good cleaning. Remove the grate above the fan blades and clean them. Carefully extract any buildup of leaves, twigs or nesting materials. Clean the condenser fins, being careful not to bend or break any blades or fins. A garden hose with a pressured nozzle can be helpful here as you work your way around the coil. Aiming the water stream can help you flush out debris from the coils and down through the fins.

Fuse check

Next step, fuse check! Your A/C unit’s disconnect blocks typically contain two cartridge fuses. You’ll want to check each of them because they are your leading indicators, tipping you off that another part inside the condenser is failing. To accomplish a fuse check, set your meter to the ohms scale on the lowest setting, touching the red and black leads to both ends of each fuse, and look for a number. If you get a number, you’re all good.  However, if your readout shows a zero, a negative or infinity, you have a blown fuse. Once you replace both the parts and the fuses, try turning on the power. If the fuse blows again, you know you still have a problem and will likely need to call a pro.

Thermostat check

Some thermostats are battery-operated and just need a new set of batteries, so start by replacing those. Test the results by setting the device to a temperature significantly lower than the room’s current temperature. Make sure your system is set to cool and not just on fan mode. A wired thermostat (not battery-operated) is a little more complicated to replace and may also require some degree of programming.

Filter check

A great way to stay ahead of problems is by changing filters on a regular basis. Dirty filters restrict airflow and make your HVAC system work harder to achieve the same goal over time. This eats into your system’s efficiency and degrades its ability to cool and heat quickly and effectively to the desired temperatures — but it can get even worse. Clogged filters, if they remain clogged long enough, can prompt your system to freeze up with ice.

Furnace check

If you turn your thermostat to the cool or A/C mode, lower the temperature, and your furnace fan starts spinning, you’ve narrowed down the problem and know your issue isn’t with the furnace. If no spinning happens, try the breaker reset again. If it’s still at a dead stop, you will need help. Meanwhile, outside in the condenser, make sure your compressor and fan are running accordingly. If not, move on to the following few ideas.

Duct check

Now it’s time for a duct check. With the system powered on and blowing, check every duct vent in your home to make sure they push out air. If air isn’t escaping steadily from any of them, it’s a telltale sign of a blockage that will require a duct-cleaning service call.

Ice melt

You don’t have to live in Alaska to find yourself stuck in the ice. As we mentioned earlier, sometimes an A/C unit can freeze up, caused by low refrigerant, a bad thermostat, poor drainage or a problem with your fan. It’s tough to tell which is the culprit, however, before getting rid of the ice. Luckily, this task is easy if you simply turn off the system and run the fan, but you don’t even need the fan to get the ice to melt. Time is all you need.

Give it some time

Speaking of time, once you try one or more of these DIY fixes, take a break. Give yourself half an hour before turning the power back on and trying to power up everything again. Machines like your HVAC unit and the computer in the thermostat have timed delays that can last 10 minutes or more. It’s frustrating to turn around from a fix only to have your system fail to reboot, so save yourself some trouble. If your repair involves any energy-saving devices, they’ll add to this delay. Go stretch out in the hammock and catch a wee power nap before firing everything up again..

Test your repairs

After your nap, reinstall any parts you left open and close all electrical access panels. Turn on the power at the circuit breaker and the furnace switch. Turn down the thermostat and see if the HVAC begins a cycle, wherein the compressor will run and the condenser fan will spin. At this point, if the compressor is active but the fan won’t spin, you need a new fan motor. Once you have that $150 part in hand, simply turn off the power, remove the condenser cover, take out the fan and motor, put the new one in, and replace the cover. Then power everything back up, from the breaker to the thermostat. If it still doesn’t spin, you need professional help.

Calling a pro

Trying all these steps can enlighten you to many potential fixes that could help you avoid calling in the pros, but sometimes a pro is exactly what you need. Don’t worry, though; you tried, and that’s what matters. There’s no shame in handing over your screwdriver to someone who is HVAC-certified.

Up for learning more? Check out our post on how long your air conditioner should last, and then look into three ways to take care of your air conditioner. If you’re wondering whether home warranties cover AC systems, we’ve got you covered.

The information in this article is intended to provide guidance on the proper maintenance and care of systems and appliances in the home. Not all of the topics mentioned are covered by our home warranty or maintenance plans. Please review your home warranty contract carefully to understand your coverage.

Your home protection is ready and waiting!