The Nitty-Gritty DIY Air Conditioner Maintenance Checklist

Posted by James Clark on Apr 6th 2022

The Nitty-Gritty DIY Air Conditioner Maintenance Checklist

Spring is practically here, meaning summer isn't too far off. 2021 was the hottest summer on record, so many of you are probably already dusting off the AC unit in preparedness for this year's summer.

But is your air conditioner ready to help you beat the heat? AC maintenance is imperative to keep your unit in good enough working condition to keep you cool.

While you may need a professional to check severe problems, you can perform DIY air conditioner maintenance . It's not too difficult to check that your AC is still running at optimal levels.

As it turns out, there's an entire air conditioner maintenance checklist you should be aware of. If you're not sure of what to do with your AC, this is where you'll learn how to maintain your air conditioner and heat pump.

The Nitty-Gritty A/C Maintenance Checklist

Below is the nitty-gritty checklist for your making sure your A/C is ready for Spring and what our service division uses as when inspecting customer's air conditioner units.

  1. Check Thermostat and Electrical Connections
  2. Check Condition of Filter and Replace if Necessary
  3. Check that Vent Registers are Open and No Return Vents are Blocked
  4. Check Operation of System to Determine Pre-Existing Conditions
  5. Check Condition of Air Handler/Furnace's Blower Motor and Blower Wheel
  6. Check and Lubricate Motors and Bearings
  7. Check Condition of Condenser Motor and Fan Blade
  8. Test Capacitors
    1. Air Handler/Furnace Capacitor
    2. Condenser Capacitor
    3. Run Capacitor(s)
    4. Start Capacitor (if equipped)
  9. Check Contactor for Signs of Pitting and Discoloration
  10. Check Voltage and Amps on Compressor
  11. Check Temperature Drop Across Evaporator Coil
  12. Check for Proper Condensate Drainage and Proper Condensate Pump function
  13. Check Line Set and Line Set Insulation
  14. Check the Condenser Coil and Clean if Necessary
  15. Check the Evaporator Coil and Clean if Necessary

And that is a comprehensive checklist in a nutshell. Read further for more detail on how to perform a Spring-time A/C maintenance yourself.

1. Check Thermostat and Electrical Connections

Make Sure the Thermostat Is Set to "Cool"

One of the most common troubleshooting people run across is their appliances aren't on. Check that your thermostat is set to either "off" or "heat," then there's likely nothing wrong. You've just got the AC turned off.

Check the Thermostat Setting

If you have put the thermostat to cool and the condenser is not turning on, the thermostat could be set too high. After you check the temperature and see that it's set the same or higher than the room temperature, change it.

Also check to see if a temperature-offset setting is applied. Some thermostats allow for temperature offset adjustments in case the thermostat is in a weird place that doesn’t effectively measure the average temp in the home; An offset can be applied to compensate for this, however, if you are trying to save money and have it set to a higher settings, you may not be reaching the minimum level of comfort you desire.

Another thing to be aware of is on some thermostats, such as the Emerson Sensi, they may have a setting enabled, called “A/C Protection”. This will keep the condenser from cycling for at least 5 minutes from the last A/C cycle. So if you put the thermostat on cool, and you don’t hear it turn on, this can be why.

Also, make sure to check that your cooling schedule is set correctly. Some thermostats can lose their schedule due to power loss, malfunction, or even people in the home messing with it.

2. Check Condition of Filter and Replace if Necessary

If your unit is struggling to keep things cool, it could be that the filter needs replacing. Turn off the furnace's power and remove the filter to check for accumulated dirt. If there's too much dirt on the filter, switch to a new one.

Rule of Thumb is to change your filter every month per inches of thickness. 1-inch filters should be changed every month, where as 2-inch can be changed every 2 months, however, this will change depending on your certain environment and personal preferences. We recommend at least checking them every month.

3. Check that Vent Registers are Open and No Return Vents are Blocked

Check your home's vent registers and make sure supply vents and return vents are open. It is common for homeowners to close off vents in rooms to save money, but too many closed vent registers causes less airflow over the evaporator coil and cause it too ice up, and end up costing more in energy bills due to the system having to work harder.

Another common mistake is to cover return grilles with furniture; This means that the air handler cannot take incoming air and causes a lack of airflow over the evaporator coil and cause it to ice up.

Also, make sure vent registers are clean and free of dust, and inspect for mold.

4. Check Operation of System to Determine Pre-existing Conditions

Once you have determined proper thermostat operation, replaced the filter and ensured vent registers are open, it’s time to fire it up and observe system operation.

Check for Noises

Check for weird noises coming for the condenser and furnace such as scraping, and rumbling. Make sure the condensing unit is clean of debris, and that there is not obstructions in the blade’s radius.

A loud humming sound from the condenser or furnace/air handler means you have a failing capacitor or your motor has already seized up. If you can catch this early, a simple capacitor replacement can fix this, and save your motor, however, if you leave this unchecked, the motors will have to work harder, and will seize up, costing you hundreds.

On the furnace/air handler side, it’s important to check for weird noises from the blower compartment such as scraping. Scraping noises could indicate a bad blower wheel as the fins might have fell off. Replace as soon as possible to prevent further damage to the unit.

5. Check Condition of Air Handler/Furnace's Blower Motor and Blower Wheel

As stated above, make sure the blower wheel is not missing and fins and is not wobbling. Also, check to make sure it is free of dust and caked-on gunk.

6. Check and Lubricate Motors and Bearings

Listen to the blower motor during operation, a rumbling sound can indicate the blower motor bearings have gone bad. Lubricate with 3-in-1 oil as a precaution. This is not necessary on ever motor as some have sealed bearing assemblies.

Do the same for the outside condensing unit if necessary.

7. Check Condition of Condenser Motor and Fan Blade

Listen and look at the condenser motor while operating. Make sure that the fan blade is in balance and that there are no obstructions in the blade’s radius. An unbalanced fan blade can cause the whole unit to shake and cause refrigerant leaks and destroy the bearings on the fan motor.

Check the nuts where the fan motor mounts to the fan grille and make sure they are secured and not rusting out. Also, check the condition of the grille itself. Over time, these can rust and cause catastrophic failure to the A/C unit when the motor drops and takes out the condenser coi.

8. Test Capacitors

  • Air Handler/Furnace Capacitor (Located near or usually on the blower housing the blower compartment)
  • Condenser Capacitor (Located in the outdoor unit inside the panel where incoming power comes in)
    • Run Capacitor(s)
    • Start Capacitor (if equipped)

Use the capacitance setting on your multimeter to ensure the capacitors are within spec. Anything 10% out of range indicates the capacitor should be replaced.

Read our comprehensive guide on testing capacitors .

9. Check Contactor for Signs of Pitting and Discoloration

Make sure that the contactor is not discolored where the electrical contacts pull in. A bad contactor can be indicative of further issues like a compressor or fan motor over-amping. Check that incoming out outgoing wire terminals are tight. If they are not, it can cause your outside fuse disconnect to trip and blow fuses.

Pro tip: When replacing a contactor, come back in a couple days to re-tighten the screws where the copper wires come in. These connections can heat up, expand and contract, and become loose.

10. Check Voltage and Amps on Compressor

Using a multimeter with an amp clamp, check the wires going to the compressor to see if amps are within spec. The operating amps of the compressor and motor are labeled on their respective dataplates/stickers.

Check for proper incoming voltage. If you don’t have an amp clamp to check amps, a voltage drop when measuring voltage will tell you the motor or compressor is pulling too many amps.

11. Check Temperature Drop Across Evaporator Coil

Airflow, airflow, airflow. This is the single most important step to tell if an A/C system is functioning correctly. So many times have we heard of technicians coming to people’s homes and overcharging systems with refrigerant because they did not check for proper air flow. Using a temperature proper on the incoming return air vent, get a temperature reading. Now probe the supply our outgoing side after the evaporator coil and get a temperature reading. We like to see at least an 18 degree temperature drop from return to supply side.

12. Check for Proper Condensate Drainage and Proper Condensate Pump Function

Next on the air conditioner maintenance checklist is more cleaning, specifically the condensate drain tube. Condensate drain lines run through central cooling systems to the outside.

Condensate drains serve as pipelines for evaporator coil condensation and humidity. The moisture ends up inside a collection pan called the "condensate pan."

After water finds its way to the pan, it drips out of a small faucet-like attachment to avoid ductwork and insulation damage via moisture build-up.

Air conditioning coils collect a lot of bacteria from the air that inevitably turns into a slimy substance. If you notice water around your AC furnace, then it's likely the condensate drain is clogged.

To unclog the condensate drain, all you need to do is unscrew the faucet-like attachment and put a few condensate pan tablets inside the drain pan. You can use a long dowel or screwdriver to push them further inside.

The tablets will help clean slime out of the pan. It's advisable to add pan tablets every month while using your AC. After adding the pills, you can install the new drainage tubing to replace the drip faucet.

You'll need a ¾ inch MIPT barb fitting, a ¾ inch I.D vinyl tubing, and tubing straps to make the new drain. First, install the barb fitting, then attach the vinyl tubing and tubing straps.

13. Check Line Set and Line Set Insulation

Check that the insulation on your outdoor condensing unit is in good shape and not rotting. This insulation is fairly cheap and easily replaced. You can find this insulation at your local hardware store.

Proper insulation keeps the line from sweating and leaking fluid into the home through the opening. Also, it can reduce system efficiency because heat is being added to the refrigerant and increases superheat.

14. Check the Condenser Coil and Clean if Necessary

Condenser fins become clogged with gunk after a while. Straightening the fins may have scrapped some of the dirt from between them, but a water hose (preferably one with a nozzle) can do the job better.

You have to be careful not to get water on the fan motor during your cleaning. Water may wash away the oil on the fan's sealed bearings.

If your motor doesn't have sealed bearings, then you can take the opportunity to check the lubrication. If the fan motor isn't looking too lubricated, you can add some electric motor oil.

15. Check the Evaporator Coil and Clean if Necessary

If you can, open your evaporator coil box and inspect to see if there is dust or debris on the blower side of the coil. Clean with a stiff nylon brush.

Keep Things Clean

Cleanliness is a vital part of AC maintenance. Regular cleaning removes dirt and other build-ups that clog your air conditioner and keep it from running efficiently.

Clogged air filters are problematic because dirt inhibits airflow and makes the unit work harder. Over time, the evaporator coil ends up covered with dust.

The dirty evaporator can't absorb heat and gets harder to cool your home. A vacuum with a soft brush attachment should be sufficient to clean the fins.

Often, air conditioners are covered with a metal frame to keep the inner mechanisms safe. You may have to remove this frame to reach the fins.

Make sure you're using a soft bristle brush when cleaning. The fins are fragile, and it doesn't take much effort to crush or bend them.

Optimize Your Home for Best A/C Performance

Your Windows Can Help Control Heat

When considering how to perform air conditioner maintenance yourself, windows probably aren't the first thing to come to mind. However, anything that can help cool your home more effectively should be considered.

Your windows can bring a lot of heat into your home. You can either opt for energy-saving windows - which are not cheap - or use less expensive methods.

Keep windows closed during the day and covered with blinds or drapes during peak hot hours to reduce heat. It's especially vital to keep windows facing the sun covered to reduce the indoor ambient air temperature.

Check and Repair Damaged Insulation

It's common for insulation to become rotted or damaged over time. Condensation on outside AC lines causes things to run less efficiently. Luckily, replacing insulation isn't a challenging task.

First, you need to remove all the old foam insulation and measure the large AC tube's diameter. Once you've done this, you can order the insulation.

However, you're not going to find this insulation at your nearest home improvement center.

You can get in contact with an online supplier or refrigeration supply dept for the required insulation tape and foam. Once you've gotten your supplies, you can cut the foam to the length of the large tube.

The penultimate step is to apply the insulating tape to the AC tube. The tape will help reduce condensation build-up on the piping. Finally, you can add the insulating foam.

The two sides of the foam will meet and adhere to each other around the piping circumference. When aligning the insulation foam, you need to be careful because you can't undo the glued ends.

Locate Air Leaks in Your Home

Sometimes DIY air conditioner maintenance may not require repairs on the unit itself. The problem could be with your house.

If you suspect air leaks in your residence, close all the windows, turn off all the fans (including exhaust fans), and turn off the furnace. Light a stick of incense and walk by all the outer walls of your home.

You can seal the hole when the smoke is blown or sucked toward something that indicates an air leak. The only problem is that the method may not be too precise. Some areas will still require a little guesswork.

Cover Exposed Soffits

A soffit is a material that makes up the underside of part of your house's architecture. Soffits are found inside and on the exterior of homes.

Soffits are usually decorative in older houses, while they protect plumbing and HVAC ductwork in newer residences. Soffits are unfortunately prone to leaking - especially ones with recessed lighting.

Sometimes the protective structures aren't readily apparent throughout homes. You may have to look at your house plans to find your soffits. You can use reflective foil (or bubble pack) insulation to close off soffits.

You'll need to clear away any preexisting insulation around the leaky area and caulk the region. Once you've laid your caulking, you can place the perfectly measured piece of foil.

However, you still have to keep the area clear of insulation if the soffit houses recessed lights. The insulation may become a fire hazard if it's more than three inches near the soffit.

Some light fixtures don't require their space to be clear of insulation as they're rated for insulation contact. The inside of the recessed light can will tell you the light's rating.

Heat-Reducing Window Film

Another AC maintenance option related to windows is heat-reducing window film. This material does what its name suggests - reduces the amount of heat entering through windows.

Heat-reducing window film can be DIY installed onto your windows in about 30 minutes (per window). The life expectancy for the film is about a decade, and you can find it in hardware and home improvement stores.

You can apply the film to any window. There are drawbacks to using film; putting it on your double-pane windows may void the warranty. You shouldn't use window film if your warranty is important to you.

How to Tell if Your Air Conditioning Unit Is Damaged

We've discussed DIY air conditioner maintenance tips throughout most of this article, but how can you tell if something is wrong? The following list will provide ways to know if your AC is on the fritz and needs repairs.

Odd Noises

One way to tell your air conditioner is acting up is if it's making strange sounds. Most units make quieter noises when they start or shut down, but abrupt, loud noises can often indicate something is wrong.

Buzzing or rattling noises could mean a loose part inside the unit. Grinding sounds indicate something serious is happening inside. Once the noises start, they're not liable to go away without intervention.

Odd Smells

We talked about freon leaks' odd smell, but it's not usual for your air conditioner to smell like anything. If there is any strange, unfamiliar scent coming from your AC, you've got problems.

Burning smells aren't a good sign. While the smell could be something harmless like dust burning off, it could also be a broken capacitor or clogged filter. A broken capacitor is rarely salvageable; expect to need a new one.

Water Leaks

Water leaks may come from melting ice build-up on the heating coils. The ice melts from contact with the furnace or because you've shut the AC to allow time for the build-up to liquefy.

Regardless of why the water melted, it's a bad sign. We've already discussed what causes the icy accumulation in detail, so we'll focus on the damage the water can do.

Leaving the leak alone could give it enough time to short out your air conditioner. The leaking water could also damage your house. Enough water build-up can sink to your basement and create mold or mildew growth.

Continuous Cycling

It's normal for an air conditioner to run cool cycles regardless of the weather. It's also expected for your AC to turn on more when it's hot out. What's strange is for your AC to cycle continuously.

If you notice your air conditioner cutting on and off, over and over, that's a telltale sign that something isn't right. You could resolve the matter with a quick tune-up, or you may need a new air conditioner .

High Humidity

Spring and summer will have hot, sticky days; it's unavoidable. However, something you should never experience with a fully-functioning air conditioner is indoor humidity.

An AC should automatically deal with humidity. If your unit has issues keeping moisture out of the air, you may need a re-calibration or other repairs. A whole-house humidifier can help keep moisture levels down also.

Working on Your Air Conditioner Maintenance Checklist?

An air conditioner maintenance checklist should ideally have everything to help your AC unit run smoothly. You should check if your AC is the right size for your house and if the filter is clean.

You can soften your air conditioner's loudness with a sound blanket. You should also remember that covering your windows is essential for DIY air conditioner maintenance.

If you're searching for replacement parts for your air conditioner, look no further than Technical Hot and Cold. We've got all the parts you need to keep our AC in excellent condition.

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About the Author

James Clark

James Clark is the HVAC Controls Specialist and Ecommerce Manager for Technical Hot & Cold. He has been with the company since 2014 and enjoys helping homeowners save money by providing help articles that walk them through various DIY HVAC repairs. In his spare time, he's playing music with his children and spending too much time working on his lawn.

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