Summer along the North Shore can turn your home into an oven fast, and nothing ruins a hot afternoon like a heat pump that won’t cooperate. Before you panic or reach for the phone, know this: there are several air conditioning troubleshooting steps you can take that may fix the problem. Some issues, though, need a trained eye and the right tools.
Ravinia Plumbing, Sewer, Heating & Electric has seen just about every AC problem homeowners can run into over the years. While we love seeing your friendly faces, we also know a surprise service call isn’t anyone’s idea of a good time (or a good use of your Saturday). We’re always happy to come by, but we’d rather help you skip the wait and the bill whenever we can.
This air conditioner troubleshooting guide and checklist will walk you through what you can check yourself. And when these DIY tips aren’t enough to solve the cooling challenge for good, see what our professional HVAC technicians do to diagnose heat pump and air conditioning issues.
What’s Working Against Your Air Conditioner All Summer
Whether you’re running a central air conditioning system or a heat pump, your cooling system works hard all summer long. Heat pumps have it a little tougher; since they handle both heating and cooling duties year-round, they experience more wear and tear over time.
However, both types of systems face the same enemies: Illinois humidity, pollen, dust, and daily temperature swings that put stress on components and force your equipment to work overtime.
DIY AC Troubleshooting Checklist
Air conditioning troubleshooting starts with a handful of simple checks anyone can do, regardless of which type of system you have.
1. Check Your Thermostat Settings
It sounds almost too simple, but a surprising number of “broken AC” calls turn out to be thermostat settings that got bumped, scheduled incorrectly, or left on the wrong mode. This takes thirty seconds and can save you an entire service call.
How to Check for Incorrect Thermostat Settings
- Look at your thermostat display. Confirm your thermostat is set to “Cool” (not “Heat” or “Fan Only”) and that the correct temperature is set, which should be lower than the current room temperature.
- Confirm the fan setting. Make sure it’s set to “Auto” rather than “On.” When the fan is set to run constantly, it can make your system feel like it’s not cooling properly, even though the compressor is cycling normally.
- Check the thermostat batteries. If your display is blank, dim, or unresponsive, swap in fresh batteries before troubleshooting further. A dying battery can cause all kinds of odd behavior that has nothing to do with your actual cooling system.
Additional Tips for Smart Thermostats
- Check the app. If you have a smart thermostat, check the app, too, since schedules or away modes can override manual settings without you realizing it.
- Change settings manually. If you have a smart thermostat connected to an app or Wi-Fi, try adjusting the temperature manually at the thermostat itself. If it responds correctly, this may point to a connectivity issue rather than an actual system problem.
- Check for a delay or lockout feature. Some smart thermostats have a built-in compressor delay (usually 3-5 minutes) to protect the system after a power interruption. If you just reset a breaker or had a power flicker, give it a few minutes before assuming something’s wrong.
- Look for an error code or alert icon. Many smart thermostats display a small icon or code when they detect a system issue. Check your thermostat’s manual or app to see what any icons on the display mean.
2. Look at Your Circuit Breaker
Power surges, storms, or an overworked system can trip a breaker as a safety measure. In many cases, you just need to check your home’s electrical panel and reset it. If it trips again shortly after resetting, that’s a sign of a deeper electrical issue, and that’s your cue to stop DIY troubleshooting and call a professional.
Power Supply Troubleshooting
- Look for a switch out of alignment. Open your breaker box and look for a switch that’s out of place. A tripped breaker usually sits in a middle position, angled differently from the rest of the switches in the panel and not fully in the “On” position.
- Turn the breaker fully off before turning it back on. Push the breaker firmly to the “Off” position first, even if it looks like it’s already partway there. This resets the internal mechanism properly before you flip it back on.
- Flip it back to “On” and listen for your system to respond. You should hear your outdoor unit and indoor blower kick on within a few minutes. If nothing happens, double-check that your thermostat is still set correctly.
3. Inspect and Replace the Air Filter
A clogged filter restricts airflow, forcing your system to work harder while cooling less effectively. This is one of the most common causes of weak airflow and can even lead to your system freezing up. Most manufacturers recommend replacing filters every 1-3 months.
How to Change a Dirty Air Filter
- Turn off your system first. Switch your thermostat to “Off” before opening any panels, both for safety and to keep dust from getting pulled into the ductwork while the filter is out.
- Locate your filter. It’s typically found in the return air duct, the blower compartment, or sometimes in a slot along the ceiling or wall near the air handler. Check your owner’s manual if you’re not sure where to look.
- Note the size and airflow direction. Most filters have an arrow printed on the frame showing which way air should flow through it. Take a quick photo with your phone if you’re worried about forgetting.
- Remove and inspect it. Keep the filter flat as you remove it to avoid shaking loose dust and debris back into your ductwork. Hold it up to a window or lamp; if you can’t see light passing through it, it’s overdue for a replacement.
- Check the size printed on the frame. Filter dimensions are usually printed along the edge. Buy a replacement filter in the exact same size.
- Insert the new filter facing the correct direction. Line up the arrow on the new filter with the airflow direction you noted earlier and make sure it fits snugly. Installing it backward restricts airflow just as much as a dirty filter would.
- Turn your system back on and note the date. Set a reminder on your phone for your next filter replacement. Pet owners and allergy sufferers may need to swap them more often than the usual 1-3 months.
4. Check the Outdoor Unit for Debris
Your outdoor unit needs unrestricted airflow to release heat properly. When it’s blocked by debris, your system has to work overtime, which drives up energy bills and can shorten the equipment’s lifespan.
Outdoor AC System and Heat Pump Care
- Take a look at your unit. Walk outside and visually inspect the outdoor condenser unit for debris buildup.
- Turn off power to the unit first. Before clearing debris, flip the disconnect switch near the unit or shut off the breaker so the fan doesn’t unexpectedly kick on.
- Clear debris from around the base. Remove leaves, grass clippings, mulch, sticks, and any weeds growing up around the unit, keeping at least two feet of clearance on all sides for proper airflow.
- Rinse the fins with a garden hose. Spray from the inside out if possible, using gentle pressure to knock loose dust and dirt without bending the delicate metal fins. Never use a pressure washer.
- Check for bent or damaged fins. Look closely at the exterior coil for any fins that are crushed or bent inward. A plastic fin comb (available at most hardware stores) can straighten minor damage, but heavily bent sections may need a professional’s attention.
- Trim back nearby landscaping. Cut any overhanging branches or bushes that have grown close to the unit since last season, and turn the power back on once everything’s clear.
5. Examine Vents and Registers Throughout the House
Even when your air conditioner is blowing cold air, vent issues can make it feel as though the HVAC system isn’t working right. Blocked vents throw off the airflow balance in your home, leaving some rooms too warm while others get plenty of cool air. Luckily, this isn’t a direct cooling operation problem and is easily fixed.
Vent Troubleshooting Tips
- Do a room-by-room walkthrough. Check every supply vent (where cool air comes out) and return vent (where air gets pulled back in) throughout your home, not just in the rooms that feel warm.
- Move furniture and other blockages away from vents. Aim for at least a couple feet of clearance in front of every vent so air can flow freely.
- Check that vent louvers are actually open. Some vents have a small lever or dial that can get bumped closed. Make sure the fins are angled open rather than shut.
- Compare airflow between rooms. Hold your hand up to a few different vents around the house. If one room’s airflow feels noticeably weaker than others, make a note of it, since this can help an HVAC professional pinpoint duct issues later if the problem persists.
- Don’t fully close vents in unused rooms. It’s tempting to shut vents in rooms you don’t use to push more air elsewhere, but this can actually throw off your system’s pressure balance and reduce overall efficiency. Keep vents at least partially open throughout the house.
6. Check for Ice Buildup on the Indoor Coil
The indoor evaporator coil pulls heat energy from your home to cool air to your desired temperature. Ice on the coil is often a symptom of restricted airflow or low refrigerant. Running your system with a frozen coil can cause serious damage to the compressor, which is one of the most expensive parts to repair.
Inspecting Your Coil
- Find your evaporator coil. It’s housed inside the air handler or within your furnace. Check your owner’s manual if you’re unsure of its exact location.
- Look for frost or ice. Open the access panel and visually inspect the coil, refrigerant lines, and surrounding area for any white frost or actual ice buildup, which can extend onto nearby copper lines as well.
- Turn your system off immediately if you spot ice. Turn off cooling mode at the thermostat so the compressor stops running completely and doesn’t keep freezing the coil further.
Thawing a Frozen Evaporator Coil
- Switch the fan to “On” to help it thaw. Running just the fan (without the compressor) helps circulate room-temperature air across the coil, speeding up the thawing process safely.
- Place towels or a pan underneath. As the ice melts, it will produce a fair amount of water, so protect your flooring while it thaws.
- Let it thaw fully before doing anything else. This can take anywhere from a few hours to overnight depending on how much ice built up. Don’t attempt to chip or scrape the ice off yourself, since this can damage the delicate coil.
- Turn your system back on. Once everything is dry, try running your AC again. If ice returns within a day or two, that’s your sign to call a professional rather than repeating this cycle.
Save This Air Conditioning Troubleshooting Checklist for Later
Ready to make sure you never miss a step? We’ve put together a free downloadable air conditioning troubleshooting checklist you can save, print, and keep handy for next time your system acts up.
When DIY Isn’t Enough: Professional AC Troubleshooting Checklist
Some issues go beyond what you can safely check or fix on your own. Air conditioners and heat pumps involve refrigerant, electrical components, and complex parts that require specialized tools and licensed expertise. Here’s what our technicians check to assess the root cause of the problem and determine the right solution.
Refrigerant Level Testing and Leak Inspection
Low refrigerant almost always means there’s a refrigerant leak somewhere in the system. Refrigerant doesn’t just “run low” over time the way gas in a car does. Handling refrigerant also requires EPA certification, so this isn’t a DIY-safe task.
Our technicians connect manifold gauges to the system’s service ports to check pressure readings against manufacturer specifications. If levels come back low, we don’t top it off and leave it at that.
We use tools like electronic leak detectors and UV dye tracing to pinpoint exactly where leaking refrigerant is escaping, whether that’s a pinhole leak in the coil, a loose fitting, or a worn valve. This way, we are able to repair the leak so refrigerant stays where it belongs.
Electrical Component Inspection
Electrical issues are a leading cause of AC failure and can pose serious safety risks, including fire hazards. A failing capacitor, for instance, can prevent your compressor from starting at all, and diagnosing it requires equipment most homeowners don’t have on hand.
Using a multimeter, we check for proper voltage, continuity, and signs of wear like scorching or corrosion on electrical components. We test capacitors, contactors, relays, and wiring connections throughout the system.
Compressor Diagnostics
The compressor pumps refrigerant through the coils so it can absorb heat from your home and release it outside during the cooling process.
If you have a faulty compressor, the whole system loses its ability to cool effectively, no matter how well every other component is working. It’s also often the most expensive part to replace if it fails completely.
We use amp clamps and diagnostic equipment to determine whether the compressor is drawing appropriate power and functioning within normal parameters. Testing the compressor allows us to determine whether a repair can fix the issue or whether the compressor itself needs to be replaced.
Ductwork Inspection
Leaky or poorly sealed ducts can waste a significant portion of your cooled air before it ever reaches your living space. This shows up as high energy bills, inadequate cooling, and rooms that never feel comfortable even when your system seems to be running fine.
Our technicians visually inspect accessible ductwork and may use pressure testing to identify leaks that aren’t visible to the naked eye. Depending on what we find, solutions can range from sealing small leaks to reinforcing loose connections, or recommending more extensive duct repairs if the damage is widespread.
Thermostat and Control Board Calibration
Sometimes what looks like a major mechanical failure is actually a miscommunication between your thermostat and the system itself. This is especially common with newer smart thermostats that aren’t compatible with older equipment.
Using diagnostic tools, we check for accurate temperature readings, proper cycling, and correct communication between components. These findings tell us whether your thermostat is sending the right signals at the right times, or whether a compatibility issue, wiring problem, or outdated control board is causing your system to misread what it’s being asked to do.
Reversing Valve Testing (for Heat Pumps)
The reversing valve switches the direction of refrigerant flow, which is what allows a heat pump to switch between heating and cooling modes. If it’s stuck, your system might blow warm air when you need cool air, or vice versa. This part is unique to heat pumps and isn’t something a standard air conditioner has.
We activate the valve using diagnostic controls while monitoring refrigerant line temperatures and listening for the valve’s shift. This tells us whether the valve is switching fully and smoothly, getting stuck partway, or failing to shift at all.
Checked Everything? Here’s Your Next Step
If you’ve worked through the DIY checklist and your system is still acting up, or if you’re seeing warning signs like ice buildup, strange noises, or a tripped breaker that won’t stay reset, it’s time to bring in a professional.
Our team offers thorough air conditioning repair services to get your home comfortable again, fast. We are also equipped to handle specialized heat pump repair for anything from refrigerant issues to compressor diagnostics.
Reach out to Ravinia Plumbing whenever your air conditioning troubleshooting turns up more than a quick fix. We’re here to help keep your home comfortable, no matter what the thermostat says outside.