9 Mistakes That Could Wreck Your AC Fast

When the summer heat kicks in, your A/C has to work overtime. But if it starts blowing warm air—or stops working altogether—it’s usually not because it’s old. A lot of A/C breakdowns happen because of little mistakes that pile up.

These are things most people don’t think twice about, but they can wear your unit out fast or flat-out wreck it. The good news? Every one of them is avoidable.

Ignoring Dirty Filters

A clogged air filter forces your system to push harder just to move air. Over time, that extra strain can overheat parts and shorten the life of the unit.

If you can’t remember the last time you changed your filter, it’s probably overdue. Most homes need a new one every 30 to 90 days, depending on pets, dust, and how much the system runs.

Closing Off Too Many Vents

It might seem smart to shut vents in unused rooms to save energy, but it doesn’t work like that. Your system is built for a specific airflow.

Closing too many vents builds pressure in the ducts, which can cause leaks and wear out the blower motor. It also messes with the balance and makes cooling uneven.

Skipping Yearly Maintenance

Even if your A/C seems fine, skipping annual maintenance is asking for trouble. A tech can spot refrigerant issues, electrical problems, and worn parts before they turn into big repairs.

It’s cheaper to get a system serviced once a year than it is to replace a compressor—or the whole unit. Think of it like an oil change for your house.

Letting the Outdoor Unit Get Overgrown

The outside unit needs room to breathe. When weeds, bushes, or fences crowd it in, airflow drops and heat builds up inside the system.

Keep at least two feet clear on all sides. Trim anything growing too close, and rinse off any dirt or grass clippings stuck to the fins.

Setting the Thermostat Too Low

Cranking the temp down to 65° won’t cool the house faster—it just makes the system run longer than it should. That nonstop cycling wears things down fast.

Most A/Cs are built to handle about a 20-degree drop from the outside temperature. Set it realistically, and give the system a chance to catch up.

Running It with a Refrigerant Leak

If your A/C isn’t cooling like it used to, and the air feels warm or weak, you might have a refrigerant leak. That kind of issue won’t fix itself.

Low refrigerant leads to frozen coils, poor performance, and serious damage to the compressor if you keep running it. Call a pro as soon as you notice a change.

Blocking the Return Vents

Return vents are how your system pulls air in. If they’re blocked by furniture, rugs, or even a pile of laundry, airflow suffers—and your unit strains to keep up.

Go room by room and check the returns. Make sure they’re wide open and nothing is sitting in front of them. It helps more than you’d think.

Letting the Drain Line Clog

That little PVC pipe near your A/C isn’t there for looks—it’s your condensate drain. When it clogs, water backs up and can trigger a safety shutoff, or worse, leak into your walls or ceiling.

Flush it with vinegar every few months or have it checked during your annual tune-up. It’s a small thing that keeps bigger issues at bay.

Replacing Parts with the Wrong Ones

If you try to DIY a fix or call someone who cuts corners, the wrong replacement part can throw your whole system off. A mismatched capacitor or cheap motor won’t last.

Always match parts to your unit’s specs. And if you’re hiring help, make sure they actually know what they’re doing. Cheap work often ends up costing more.

*This article was developed with AI-powered tools and has been carefully reviewed by our editors.