When your home's heating or cooling system isn't working or performing as expected, knowing how to troubleshoot your HVAC system can save you time, money, and frustration.
This residential HVAC troubleshooting guide outlines the key steps to take to identify common problems associated with your air conditioner or furnace.
If troubleshooting your HVAC doesn't help, call ARS/Rescue Rooter to find a professional near you at (866) 399-2885.
Step-By-Step HVAC Troubleshooting Guide
- Step 1: Check the Power
- Step 2: Check the Thermostat
- Step 3: Reset the HVAC System
- Step 4: Inspect the Air Filters, Vents, and Ductwork
- Step 5: Examine the Outdoor Unit and Airflow
- Step 6: Look for Refrigerant Leaks and Odd Noises
- Step 7: Check the Pilot Light (for Gas Furnaces)
- When to Call a Professional
- ARS Is Here to Help with All Your HVAC Needs
To help you better understand the basics of how an HVAC system works, check out The Ultimate HVAC Guide for Homeowners. Once you understand the fundamentals, follow the steps below for troubleshooting your HVAC system. If you have a mini-split HVAC system, check out our specialized troubleshooting guide.
Step 1: Check the Power
Before diving into complex fixes, take a look at your system and make sure it is receiving power:
- Circuit breaker: Locate your electrical panel and check for tripped breakers. If the breaker for your HVAC system is off, flip it back on.
- Power switches: HVAC systems often have dedicated power switches near the indoor and outdoor units. Confirm that these are turned on.
- Fuses and GCFI outlets: If your system has tripped a GCFI outlet, resetting the outlet may resolve the issue. If it has blown a fuse, it will need to be replaced. We recommend calling a professional for fuse replacement.
Pro tip: If the switch on your panel doesn't already identify the HVAC breaker, once you find the right one, label it in permanent marker to make it easy to identify the next time.
Step 2: Check the Thermostat
If your HVAC unit isn't responding, the thermostat could be the culprit. Follow these steps to inspect it:
- Check that the thermostat is on.
- Check and replace batteries if they're old or weak.
- Make sure the thermostat is set to the correct mode (heating or cooling).
- Adjust the temperature to be higher than the room's current temperature (for heating) or lower (for cooling). Then wait to see if the system turns on as it should.
- Look for loose wires (call a professional if you see any) or dust buildup inside the thermostat.
- Consider upgrading to a smart thermostat for improved energy efficiency and remote control.
Step 3: Reset the HVAC System
You've probably heard IT experts recommend turning a device off and back on to resolve glitches—this same logic applies to your HVAC system. Resetting your system can often fix minor issues:
- Turn off the system at the thermostat.
- Switch off the breaker connected to your HVAC.
- Wait at least five minutes before turning the breaker back on.
- Restore power to the thermostat and set it to your desired temperature.
Step 4: Inspect the Air Filters, Vents, and Ductwork
Dirty air filters are a common cause of weak airflow and HVAC inefficiency. They are also the easiest HVAC maintenance you can do yourself. To check your filters:
- Turn off your HVAC system before inspecting the filter.
- Hold the filter up to a light source. If little to no light passes through, it's time for a replacement.
- Change air filters every 1-3 months (or monthly if you have pets or allergies).
It's also a good idea to check that vents and registers are open and free from obstructions like furniture or curtains. HVAC dampers can also affect airflow. Check out our damper guide to find out how to check your dampers.
For ductwork, look for visible gaps or damage in exposed ducts. Leaky ducts can lead to energy waste and uneven heating or cooling. These can easily be fixed with HVAC foil tape or mastic sealant.
If there is restricted or reduced airflow in certain areas of your home, inspecting the ductwork can reveal blockages. If your inspection reveals blockages or you haven't cleaned your ducts in the past 5-7 years, ARS can provide professional air duct cleaning.
Pro tip: To test the efficiency of your AC system, measure the temperature drop between the return air vent and the nearest supply vent. A difference of 15-20°F indicates it's cooling effectively.
Recommended reading: HVAC Stories That Will Make You Shiver
Step 5: Examine the Outdoor Unit and Airflow
Depending on the system you have installed, the outdoor unit of your HVAC system can be responsible for both heating and cooling.
In cooling mode, the outdoor unit is the condenser. It releases heat absorbed from inside your home. In heating mode, if you have a heat pump, the outdoor unit works in reverse to absorb the heat from outside and bring it inside. For traditional systems, the outdoor unit's primary job is to handle the cooling.
No matter what system you have, you can improve airflow by:
- Clearing away leaves, grass, or debris from around the outdoor unit
- Inspecting the condenser coils for dirt buildup—if dirty, clean them along with coil cleanser
- Checking the fan blades for damage or obstructions—with the system off, cleaning the blades and tightening any loose screws can prevent wobbling or noise issues
HVAC and plumbing issues in older homes often occur just because of age. HVAC units generally only last 10-15 years. If your system is in that range or older, consider a replacement. Check out our guides on HVAC upgrades to consider and questions to ask your installation company when getting a new system.
Step 6: Look for Refrigerant Leaks and Odd Noises
Low refrigerant levels can prevent your system from cooling properly. Signs of a refrigerant leak include:
- Warm air coming from vents
- Ice buildup on refrigerant lines
- Hissing sounds near the unit
Since handling refrigerant requires specialized training, contact a licensed technician for AC repairs.
Step 7: Check the Pilot Light (for Gas Furnaces)
If your home has a gas furnace, the pilot light's condition can indicate a problem:
- Locate the pilot light on your furnace and inspect its flame color. A blue flame indicates it's working correctly. A yellow/orange flame indicates a potential monoxide risk; contact a professional immediately.
- If the pilot light is out, follow your furnace's manual instructions to relight it.
- If the pilot continues to go out, your thermocouple may need replacement. ARS can take care of any of your furnace repairs.
Check out our guide on how to know if it's time to replace your furnace.
Still having trouble? Let ARS handle it! Call (866) 399-2885 or book your service online today.
When to Call a Professional
Our job is to make your home comfortable and safe year-round with a functioning HVAC system, but how do you know if a professional is actually needed?
Contact a professional if you experience:
- Power failure despite performing your HVAC troubleshooting
- Frequent cycling on and off
- Water leaks or signs of mold around the unit
- Persistent odors or burning smells
While these are some of the obvious reasons to call ARS, it all boils down to this:
- No time? Call a professional.
- Troubleshooting doesn't work? Call a professional.
- Need an inspection? Call a professional.
- Work too complicated? Call a professional.
- Safety in question? Call a professional.
We've got you covered, no matter the issue. ARS is a nationwide network of company-owned locations offering heating, air conditioning, plumbing, sewer, and drain services to homes and businesses.
ARS Is Here to Help with All Your HVAC Needs
Taking charge of your HVAC maintenance can prevent costly repairs and make your system run efficiently. Our courteous and professional technicians, plumbers, and home comfort advisors are dedicated to delivering exceptional service and ensuring every job is done right the first time.
When you find new repairs are needed or it's time to have a new HVAC system installed, let ARS handle the job. Our 100% Satisfaction Guarantee means we stand by our service, and you can expect courteous and professional technicians every time!
