The US Department of Energy found that up to 90% of AC and heat pump systems have faults caused by poor installation or inadequate maintenance. When duct leaks are included, nearly every system is affected. These issues silently increase your energy bills, reduce comfort, and lead to costly breakdowns.
As an HVAC technician with years of experience, I witness these mistakes everywhere, from homes to businesses. In this blog, I’ll share the top HVAC maintenance mistakes I encounter and how you can avoid them to protect your investment and stay comfortable year-round.
 Key Takeaways
- Most homes and businesses have HVAC issues they don’t even know about.
- Forgetting to change your filter can quietly ruin your system.
- A yearly tune-up is like an oil change; skip it, and you’ll pay later.
- Leaky ducts can make you lose comfort and money every month.
- DIY fixes often turn small problems into expensive repairs.
- Heat pumps work year-round; they need year-round care, too.
- Odd smells or sounds from your HVAC? Don’t ignore them, act fast.
1. Ignoring HVAC Filter Changes
Let me start with the biggest one: filters. It’s incredible how many people either forget or underestimate how important it is to change their HVAC filters regularly.
I once visited a home where the system was barely blowing air. The family was ready to replace their whole unit. When I opened it up, the filter looked like a fuzzy grey carpet, clogged solid. That filter hadn’t been changed in over a year. After replacing it, the airflow instantly improved, and the system ran fine.
What Should You Do?
Most filters need changing every 1 to 3 months, depending on your system, usage, and whether you have pets or allergies. Set a reminder on your phone or calendar. Trust me, this one simple habit can prevent expensive breakdowns.
2. Skipping Annual HVAC Tune-Ups
You wouldn’t drive your car for years without getting it serviced, right? But somehow, many folks skip regular HVAC tune-ups.
I had a restaurant client whose AC kept short-cycling during the summer rush. Their staff was miserable in the kitchen. When I checked the system, the coils were filthy and refrigerant was low. A basic annual inspection would’ve caught both issues before they became a problem.
What Should You Do?
Schedule professional maintenance at least once a year, twice if you use both heating and cooling heavily. During a tune-up, we check everything: refrigerant levels, coils, electrical components, thermostat calibration, and airflow.
3. Blocking Air Vents And Returns
You’d be surprised how often I see furniture shoved right in front of vents or return grilles.
A homeowner once told me their bedroom was always hot. When I walked in, the only vent in the room was buried behind a heavy bookshelf. The system couldn’t circulate air properly.
What Should You Do?
Keep all vents and return air grilles clear of furniture, rugs, and drapes. Your HVAC system needs proper airflow to function efficiently.
4. DIY Repairs Without Proper Knowledge
I respect people who like to take care of things themselves. But HVAC systems are complex, and I’ve seen DIY fixes make things worse.
A homeowner once tried to fix a “simple noise” by opening the outdoor unit and adjusting a few wires. He ended up shorting the control board. What would’ve been a $150 repair turned into a $900 replacement.
What Should You Do?
Stick to basic maintenance like changing filters and clearing debris around the outdoor unit. Leave electrical, refrigerant, and mechanical work to licensed pros.
5. Letting Landscaping Overtake The Outdoor Unit
I’ve seen outdoor units covered in vines, buried in mulch, or surrounded by tall grass. That might not seem like a big deal, but it chokes off airflow and causes the unit to overheat.
At one property, a bush had completely wrapped around the unit, trapping heat and dirt. The compressor finally gave out during a 100-degree day.
What Should You Do?
Keep at least 2 feet of clear space around your outdoor condenser unit. Trim shrubs, remove weeds, and clear away leaves or grass clippings regularly.
6. Closing Too Many Vents In Unused Rooms
It seems logical: why cool or heat a room you’re not using? So, people close vents thinking they’re saving energy.
In reality, your HVAC system is designed for balanced airflow. Closing too many vents increases pressure and can cause duct leaks, short cycling, or even damage to the blower motor.
What Should You Do?
Instead of closing vents, consider upgrading to a zoning system or using a programmable thermostat to adjust temperature settings for unused rooms.
7. Not Paying Attention To Strange Noises Or Smells
Sometimes people hear a rattle or smell something musty and just ignore it. That’s almost always a warning sign.
A homeowner once ignored a burning smell for weeks until the blower motor completely seized. Had they called earlier, it would’ve been a minor belt replacement.
What Should You Do?
Trust your senses. If your HVAC system sounds or smells off, get it checked. Early detection can save you hundreds (or thousands) in repairs.
8. Neglecting Thermostat Issues Or Poor Placement
One time, I walked into a home where the thermostat was placed right next to a sunny window. The temperature reading was way off, making the system cycle constantly. Poor placement or a malfunctioning thermostat can throw your whole HVAC system off balance.
What Should You Do?
Make sure your thermostat is placed in a central area away from direct sunlight, drafts, or heat sources. If it’s old or inaccurate, consider upgrading to a smart thermostat for better control and efficiency.
9. Forgetting To Check Or Seal Ductwork
I’ve seen homes with beautifully maintained HVAC systems, but they’re losing tons of cooled or heated air through leaky ducts. A customer once complained that their utility bills were sky-high. After inspecting, we found major leaks in the attic ductwork.
What Should You Do?
Get your ducts inspected every few years. If they’re leaking, sealing, or insulating them can dramatically boost efficiency and comfort.
10. Ignoring The Drain Line Or Pan
In humid areas like here in Texas, a clogged condensate drain line can cause water damage or mold growth. I’ve been called into homes with ceiling leaks, only to find the drain line clogged with algae.
What Should You Do?
Flush your HVAC drain line every few months with a bit of vinegar or have it checked during your regular maintenance visit. Make sure the drain pan isn’t cracked or overflowing.
11. Neglecting Heat Pump Maintenance in Winter and Summer
Heat pumps work year-round, both heating in the winter and cooling in the summer. I’ve seen plenty of homeowners assume their heat pump only needs attention during the hotter months. That’s a big mistake.
One customer called us in December because their home wouldn’t heat properly. Turns out, the outdoor unit was iced over and hadn’t been cleaned or serviced in over two years. A routine checkup could have caught that before winter even started.
What Should You Do?
Have your heat pump professionally serviced at least twice a year, once before the cooling season and once before the heating season. This keeps both functions running efficiently and helps prevent system strain and failure.
12. Overlooking Hidden Duct Leaks and Damage
Ductwork is out of sight, so it’s easy to forget. But damaged or leaky ducts are one of the most common causes of energy waste I find in both homes and businesses.
At one office building, we discovered that nearly 30% of conditioned air was being lost through poorly sealed ducts. Employees were constantly adjusting the thermostat, thinking the system was failing, when really, the ducts were bleeding air behind the walls.
What Should You Do?
Schedule a duct inspection every few years, especially if your energy bills are unusually high or certain rooms stay too hot or cold. Proper sealing and insulation can drastically improve efficiency and comfort.
Final Thoughts: Don’t Let Neglect Cost You
I’ve seen firsthand how a little prevention goes a long way. HVAC systems are a big investment. With simple, smart maintenance habits, you can extend your system’s life, improve comfort, and lower energy costs.
If you’re unsure about anything, give your local HVAC technician a call. We’re here to help not just when things break, but to make sure they don’t.
When To Change HVAC Filter?
We recommend checking your HVAC filter once a month and changing it every 1 to 3 months, depending on system usage, air quality, and whether you have pets or allergies.
What Are Early Signs That My HVAC System Needs Professional Attention?
If you notice uneven temperatures, strange noises, musty smells, or unusually high energy bills, it’s time to call a technician. These are early indicators that something may be wrong.
Can Closing Vents in Unused Rooms Really Harm My System?
Yes, closing too many vents increases static pressure, which can damage ductwork, reduce system efficiency, and lead to expensive repairs over time.
Why To Change HVAC Filter?
A dirty filter restricts airflow, forces your system to work harder, reduces efficiency, and can lead to breakdowns or poor indoor air quality. Changing it regularly protects your comfort and your wallet.
How Often Should I Schedule HVAC Maintenance If I Have Both Heating and Cooling?
We suggest two tune-ups per year, one in spring for cooling and one in fall for heating. Regular checks help prevent seasonal breakdowns and keep everything running smoothly.
