Top 10 tips to fixing Your Central Air Conditioning (ac repair): A DIY Guide

If your central air conditioning (ac repair) system fails during a hot summer day, you may have to wait days, if not weeks, for a repair technician to fix it, and it’s likely going to cost you a few hundred dollars. However, if you’re comfortable working with electricity and willing to spend less than $100 on parts, you can probably fix your air conditioner yourself in about two hours. Here’s how.

Before you begin, you’ll need a few basic tools, including a multimeter, a voltage detector, an assortment of insulated screwdrivers, and a socket set.

Step 1: Check the Thermostat

Start by setting your thermostat to AC mode and lowering 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. Call a professional if the fan still won’t start as the fixes shown here won’t work.

Step 2: Check the Outside Unit

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.

Step 3: 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.

air conditioning (ac repair) system fails
air conditioning (ac repair) system fails

Step 4: Replace Faulty 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.

Step 5: Clean the Unit

It’s easy to clean an air conditioner condenser, and it’s one of the regular maintenance tasks that will extend the life of your unit. Aim your garden nozzle upward into the top of the condenser coil to remove the crud buildup under the lid. Work all the way around the coil. Then aim the nozzle down and flush the debris down the coil fins. Adjust the nozzle to a gentler stream and shoot water directly into the coils to flush out any remaining debris.

Step 6: Check for Blown Fuses

Many disconnect blocks contain two cartridge fuses. Check them before you proceed with repairs. A blown fuse is a sign of a failing part inside the condensing unit. So don’t just replace it and think you’ve solved the problem. Instead, replace the parts, install new fuses, and fire up the unit. If it blows again, call a professional.

Set your multimeter to the lowest Ohms scale and touch the red and black leads to opposite ends of each fuse. If you get a numerical reading, the fuse is good. A zero, a minus symbol, or an infinity symbol (∞) indicates a blown fuse.

Step 7: Check the Electrical Conduit

Follow the electrical conduit from the house to find the access panel. With the power off, remove and store the access-panel retaining screws and remove the panel. Before you replace any parts, check for rodents’ nests or evidence of chewing on wires and electrical connectors.

Step 8: Cleaning the Air Filter

A dirty air filter can cause your AC system to work harder, reducing its efficiency and increasing your energy bills. In addition, it can also cause the system to freeze up, preventing it from cooling properly. Therefore, it is important to clean or replace your air filter regularly to maintain proper airflow and ensure efficient cooling.

To clean your air filter, first, turn off your AC system. Locate the air filter, which is typically located in the return air duct or in the blower compartment of your furnace or air handler. Remove the filter and use a vacuum cleaner to remove any dust or debris. If the filter is reusable, wash it with water and let it dry before reinstalling it. If the filter is disposable, replace it with a new one.

Step 9: Cleaning the Condenser Coils

Over time, the condenser coils in your AC system can become dirty and clogged with debris. This can cause the system to work harder and reduce its efficiency. To clean the condenser coils, turn off your AC system and use a soft brush or vacuum cleaner to remove any dirt or debris from the coils. You can also use a fin comb to straighten any bent fins.

Step 10: Checking the Refrigerant

Levels Low refrigerant levels can cause your AC system to not cool properly. To check the refrigerant levels, you will need a refrigerant gauge and a charging hose. First, turn off your AC system and locate the refrigerant lines. Attach the charging hose to the service valve and the gauge to the hose. Open the valve and check the gauge reading. If the reading is low, you may need to add more refrigerant to the system. However, it is important to note that adding refrigerant is a job best left to professionals.


As you can see, there are several common AC repairs that you can do yourself with a few basic tools and some DIY skills. However, it is important to note that if you are not comfortable working with electricity or if the repairs require more complex skills or knowledge, it is best to call a professional AC repair technician. By taking care of your AC system and performing regular maintenance, you can ensure that your system operates efficiently and keeps you cool all summer long.

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