How to Fix an Air Conditioner

Unfortunately, the majority of cooling system problems become apparent when the unit is at its greatest use during hot summer weather.

If you are a do it yourself minded homeowner, this situation presents an opportunity to troubleshoot your whole house air conditioning or heat pump unit without having to call a professional.

Although you won’t be able to complete every aspect of air conditioner maintenance and/or repair, in many cases, you can have your unit up and running by performing basic maintenance procedures followed by possible replacement of a few key components that are often the first to fail on any whole house cooling system.

Troubleshooting Starts With the Primary Problem

When troubleshooting an air conditioner, first determine what the primary issue seems to be.

Perhaps you’ve been noticing that your home is not particularly comfortable on hotter days, or that the amount of airflow exiting your ductwork is lower than normal.

In some cases, your unit may fail to turn on at all. With this very simple starting place, you can begin searching step by step for whatever problem is keeping your cooling system operating poorly.

When Your Air Conditioner Won’t Turn On…

Coming to the realization that your air conditioner won’t turn on doesn’t necessarily mean you’re in for a big repair bill. Check your thermostat as outlined above, then look for a tripped a breaker in your circuit box.

If you’ve completed the maintenance procedures previously mentioned, are certain that your thermostat is set correctly, and have verified that your cooling system is receiving power but you still can’t get the unit to turn on, you may be dealing with the failure of one or more small parts responsible for proper electrical connections within your system.

The contactor and the start/run capacitor(s), both located within the exterior portion of your cooling system, are inexpensive items that can be replaced by do it yourself minded homeowners comfortable working with wiring. Complete the procedure with the following steps:

1. Purchase the appropriate contactor

Purchase a replacement contactor and the appropriate number of start/run capacitors at a local appliance store, furnace dealer, or online. You will need your unit’s make, model, and serial number to ensure you receive the correct part.

2. Use a multimeter to check the fuses

Located within the exterior shut off box attached to your air conditioner AFTER you have completely shut off the power to your HVAC system.

Any numerical reading on your meter indicates the fuse(s) are still good, but a zero or negative reading means they need replacement. Don’t assume that replacing a blown fuse is the answer to your troubles; fuses tend to blow when one or more parts require replacement. If, after completing the following repairs, you continue to blow fuses, it’s time to contact a professional technician.

3. Locate and inspect the unit’s access panel

By following the electrical conduit that leaves your house and leads to the exterior compressor/condenser. Remove the panel, then inspect for any nests or chewed wires; if you feel comfortable, you can clean and/or repair any damage caused by rodents or other pests.

Be sure to discharge the start/run capacitor first by creating a short with an insulated screwdriver between the two terminals of single mode capacitors, or between the “H” and “C” terminals followed by the “F” and “C” terminals on dual capacitors.

4. Replace the old capacitor

By using needle nose pliers to move the wires from the old capacitor to the new one, one at a time, AFTER you have discharged the old unit. Make sure the wires are tight, then secure the new capacitor with the bracket screw.

5. Replace the old contactor

In the same manner as the capacitor, moving the wires from the old to the new component, one at a time. Check for tightness and secure the new part.

6. Replace the access panel door, power up your unit and hope for the best!


Improved Airflow Leads to Greater Efficiency

Air conditioners that are operating at less than their optimal level of efficiency tend to have a difficult time keeping any home comfortable. Maybe you have noticed that your system has gradually become more sluggish and just can’t keep up with the hottest weather conditions.

By completing the following troubleshooting and maintenance steps which focus primarily on improving the airflow of your unit, you can often increase the efficiency of your system dramatically. These procedures are also recommended as preventative maintenance and will extend the lifespan of your HVAC equipment:

1. Check your thermostat

This may seem obvious, but the first place to start anytime your home is not comfortable is at the thermostat itself. Make sure the unit has fresh batteries and is set to “Cool” with the fan set to “Auto” or “On”, then verify that you have properly entered the desired temperature.

Bear in mind that a poorly located thermostat can cause your air conditioner to stop running prematurely or keep running far beyond what is desirable; consider moving your unit if it is located in direct sunlight, near a hot stove or a register vent, or if you’ve recently completed a remodeling or add on home improvement project.

2. Change your air filter

If you haven’t been changing your air filter every 30-60 days, you may be taxing the motor on your A/C unit, causing a drop in efficiency. A clogged filter restricts airflow, significantly reducing your air conditioner’s ability to cool your home.

3. Remove debris from the exterior compressor/condenser

Begin by completely shutting off the power to your HVAC system; flip the appropriate switch(es) not only at the main breaker box but also at the exterior shut off box which should be located near the exterior portion of the system.

Once your unit is safely powered off, remove the fan cage from the top of the compressor/condenser with the help of a screwdriver and/or wrench. You can then remove any leaves or other debris from the inside of the unit with your hands or a wet/dry vacuum.

4. Clean the fins from the inside out


With the fan cage still removed, use a garden hose to clean the fins of your unit from the inside out, dislodging any debris. If water alone is not enough to fully clean the fins, a commercially available cleaner can be used to aid the process.

5. Straighten bent compressor fins

Since proper airflow is critical to optimal functioning of your air conditioner, any bends in the fins of the exterior portion of the system should be carefully straightened with the help of a special straightening tool.

You can complete this step with a butter knife, but use extra care not to puncture the metal as the narrow tubing contained within is easily damaged.

6. Create at least two feet of clearance around the unit

Take away leaves and debris and keep grass cut low to allow proper airflow on all sides of your unit.

7. Cover the refrigerant lines with insulating sleeves

Make sure the two copper pipes responsible for the movement of refrigerant in and out of your home are properly insulated with foam sleeves for maximum efficiency.

8. Check the level of your air conditioner’s outdoor component

Because concrete slabs can sink and shift over time, your air conditioner’s exterior component may no longer be level. Unless you have a heat pump which should gently slope away from your home to direct winter defrost away from your foundation, using shims to bring your unit back to level will improve its efficiency and lengthen its lifespan.

9. Change your system’s blower filter

Above and beyond the regular monthly replacement of the more easily accessible air filter(s) located behind your system’s central air return register(s), many HVAC systems also utilize a separate filter located inside the air handler’s blower compartment.

This filter should be changed twice per year or more often in dusty locations. Purchase a new filter with the same “MERV” rating as the old one, being careful to align the filter in the proper direction. This is not a good location to use a “HEPA” or other air purifying type of filter, as they have a tendency to reduce airflow.

Once you have completed the checklist above, it’s time to power your air conditioner back on and check for improvements. Be patient when waiting to hear your unit click on; some systems are designed with a 10 or more minute delay after being switched off.

If, after 30 minutes have passed, your air conditioner still isn’t performing well, you can assume you have yet to discover the root cause of the problem.

Maintenance For the Interior Components of Your Air Conditioner

In addition to regular replacement of air filters, additional indoor components of your cooling system require periodic maintenance.

When airflow is significantly blocked, for example, the evaporator coil located within your air handler may ice over; turning your thermostat to “Off” but leaving the fan switched to “On” should correct this issue in short order, assuming you’ve already improved the overall airflow of your system.

Evaporator coils themselves benefit from periodic cleaning with a soft brush and a commercially available spray on, no rinse product. As before, be sure to cut the power to your air conditioner before attempting to clean the coils!

This is also a good opportunity to check for puddling in the drain pan that lies beneath the evaporator coil, as poor cooling can also be caused by a clogged drainage line. Follow the drain line to wherever it exits your home, then use a wet/dry vacuum held against the end of the tube with duct tape for several minutes to remove algae or other growth that my be clogging the pipe.

Do It Yourself Minded Homeowners Save Time and Money

Provided you use care when completing the above procedures, you have a good chance of improving the overall efficiency of your air conditioner or of getting it up and running again.

Proactive do it yourself homeowners will not only appreciate significant financial savings but are likely to benefit from faster results by eliminating the wait time for a technician to arrive.

When All Else Fails, Call In a Pro

If you have completed the steps listed above and still don’t have an A/C unit that is functioning efficiently, it may be time to contact a professional HVAC technician.

You may be dealing with a refrigerant leak or a problem with the compressor or the evaporator coil. Take heart in knowing that you’ve already completed a significant portion of maintenance and repairs, meaning your service call will be streamlined to cover only those issues that simply have to be handled by a pro.

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