AC Repair: Your Step-By-Step Troubleshooting Guide for Fixing AC Issues

Owning your own home is full of advantages. You can personalize your rooms any way you want, knockdown and put up walls on a whim, and load up your house with pets if that’s what you feel like doing. But you also have to deal with all the drawbacks of maintenance and repairs.

One of the most expensive and stressful problems homeowners complain about is their air conditioning units. When your AC goes down, especially on a hot day, life can get pretty miserable.

Calling a service tech out is an expense no one wants to deal with. In most situations, an AC unit that isn’t working is a simple fix. If you know a few essential tips to troubleshoot your way around the unit, you could save a lot of money.

Unless you’re familiar with big machines, fixing your air conditioner yourself can be a bit intimidating. This guide will take you step-by-step into the DIY world of troubleshooting the most basic AC repair needs before you have to call in the pros.

1. Check the Filter

The first step to troubleshooting a faulty air conditioner unit is to check for the easiest possible solution. Something as simple as a dirty AC filter clogging up the system may be the issue.

Air filters serve as a barrier between the air and the expensive equipment. They prevent dust and debris from getting into the HVAC (heating, ventilation, air conditioning) unit.

To keep the clean air flowing and prevent damage to the machine, you should regularly change your filter. The more the filter clogs up, the harder the unit has to work. This causes wear and tear on the parts and eventually can lead to expensive repairs.

It turns into a massive problem that has a straightforward, preventative fix. All you have to do is check your air filter monthly and change it if it’s starting to fill with junk.

Steps to Change Your Filter

If you never changed an air filter before, there’s no time like now to learn! It’s a fundamental DIY part of owning or renting a home. All you need is a stepladder and a new filter.

Then you can follow these steps:

  • Find the air filters in your home. These are often with the return air duct in your ceiling or on a wall. There may be more than one. If you can’t find yours, ask your landlord or call your HVAC technician to help you.
  • Open the panel to find out what filter you need. You might be able to see this without opening anything. However, it’s usually a simple hook or finger-twistable screw that keeps the panel closed. Opening it gives you an idea of how dirty the filter is, too.
  • Buy your new filter. A label with the size of the filter you need is on the side of the old one. Most filters are available at Walmart or a hardware store. If yours is an uncommon one, you might need to order a set online.
  • Turn your unit’s power off. When you’re ready to change the filter, always make sure there is no electricity running to the AC. This is for your safety and to make sure nothing gets sucked straight into the unit when you’re changing the filter.
  • Remove the used filter; insert the new one. Open the panel again and have your new filter next to you. Filters should slide in and out of the opening easily. As you pull the old one out, watch how it is tucked in and in which direction it is facing. Then, open your new one and slide it in the same way.
  • Close the panel and discard the old filter. The safest way to remove an old air filter is to put it in a plastic bag and throw it outside in your trash can. That way, its dirt and debris aren’t recirculated in your home.

Changing your air filter is the fast, simple way to prevent a significant problem. But if this didn’t fix your AC issues, there might be a blockage in other places.

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2. Check Out the Surroundings

If your air doesn’t seem like it’s cooling the way it should be, there could be a problem with the unit. Before you call in an expert, though, look at what you have in the same room as the HVAC system.

Appliances that run on electricity generate extra heat. If you have a few of them near your AC, it’s going to need to run harder to cool down the area.

It might also be that you need to seal the windows and doors in the room better. When air is always leaking, it’s hard for your unit to reach the programmed temperature and stay there.

There are several signs you have a sealing problem somewhere in your home, like:

  • Rotten or moist wood around your window/door frame
  • Cloudy windows that don’t clear up with cleaner because the cloudiness is from inside the panes of glass
  • Chilly drafts of wind that you can feel when you’re near the window or door
  • Small puddles of condensation or dampness in a spot by the window or door
  • Visible drips or leaks around an area

If you do have these signs of a sealing problem, you don’t need an AC tech. You do, however, need to seal your windows or doors better. That’s a different DIY problem or the job of a handyman.

3. Verify Your Thermostat is Working Right

smart home thermostat
When there are no leaks, and the filter didn’t fix your AC issues, the next step is to check out your thermostat. This is an automated mechanism that can become faulty. If that happens, the AC unit gets confused.

If your thermostat shows one temperature, but the unit is cooling at another, that’s a thermometer issue. The unit is trying to operate well, but the thermostat continues to “tell” the AC machine that it needs to keep running.

A messed-up thermostat is an uncomplicated fix. Today’s thermostats are digital and energy-efficient, with smart thermostats that you can operate with your phone.

Replacing your obsolete thermostat can save you money. Troubleshooting the one you have, though, is as easy as checking if you need to clean it. Thermostats also act up if they’re not level since they can’t “read” the temperature accurately.

When you’re standing by your thermostat, look at the natural lighting around it. If it’s hung in direct sunlight, it tends to deteriorate faster. Cover the window better or call a technician to see if it’s possible to move your thermostat somewhere else.

Fixing your thermostat could be a free or inexpensive repair. If that doesn’t do the job, don’t give up yet!

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4. Make Sure Your Unit Can Breathe

An air conditioning compressor needs a lot of space around it for ventilation. Your compressor is in the back of the air conditioning unit, in the part that hangs outside. This outdoor unit also houses your condenser, condenser coil, and fan. You must keep this area tidy, especially in harsher climates.

Often, a compressor that isn’t working or is running too hard has something blocking the airflow. Troubleshoot your system by going outside and checking the yard around the unit.

Have you mowed recently? If so, did the grass pile up and clog the compressor? If not, you should check your yard for debris.

Are there weeds, furniture, or other objects obstructing the ventilation? If so, clear them out and see if that helps.

A compressor that won’t turn on at all could be a sign that something is clogging it up from the inside. In many cases, this is the sad evidence that an animal, usually snakes, climbed into the unit and died.

Since the outside compressor is dangerous and complicated, it’s better to call a technician if you think the problem is inside it. Before you do, though, there’s one more thing you should do.

5. Check the Circuit Breaker

As a homeowner, you must know where your circuit breaker is. Several factors can trip the breaker at any time, particularly in older homes. If you lose power in one section of the house and not the whole home, it’s usually a circuit breaker issue.

A unit that trips the breaker once is a simple fix. If it keeps happening, though, there’s more going on that you shouldn’t ignore.

Common causes of your AC unit tripping a breaker include:

  • Dirty air filters
  • Not enough refrigerant in the unit
  • Problems with coils (they could be dirty or broken)
  • Aging parts inside the unit
  • Broken parts in the unit

If it’s the first time your AC unit tripped the breaker, you can reset it, and that should fix the problem. However, if it happens again, and you change the filter regularly, your unit has a problem. Time to call a tech!

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6. Call a Technician

outdoor ac unit

With these DIY troubleshooting tips tried and an AC unit that still doesn’t work, you’ve done the lion’s share of the job. Now, it’s time to call a technician.

AC repairs can get complicated. An air conditioning specialist is an expert in all things HVAC-related. Sometimes, leaving the problem up to the professional is the smartest and most cost-effective thing to do.

When an AC repair isn’t one of the above simple fixes, it moves into the realm of “things to leave to the pros.” That doesn’t mean it will be an expensive problem, but it can be difficult or require professional tools to handle. If you do it yourself, you could make the situation worse.

AC system issues that a tech can handle much easier than you can include:

  • Refrigerant leaks
  • Faulty fan relays or motors
  • Mold in the air conditioning system
  • AC units that aren’t powerful enough for the space they are cooling
  • Faulty or broken parts in the compressor
  • Problems with the heat pump

Also consider whether your unit is under warranty or not. If it is, trying to fix anything yourself beyond this guide could void your warranty.

If you have warranty coverage, the company that installed the unit is who you need to call, regardless of pricing. That way, if there is a more expensive or complicated problem, the air conditioning repair service is at least partly covered.

Calling a repair technician to prevent more severe complications with your AC unit is a smart financial move. It might just need a tune-up, or there could be a need for a serious air conditioner repair.

Reviewing your warranty is a good idea, anyway, since you might have maintenance plans you didn’t know about.


If your temperatures get really high or low where you live, you need your HVAC unit in good shape. Like Murphy’s Law, though, it usually stops working right when you need it most.

Before you stress and call a service tech to fix your unit, take a few minutes to run through this troubleshooting guide. These essential tips could help you keep the hundreds of dollars you were going to pay the experts. Keep that money in your pocket!

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