Why Is My AC Blowing Warm Air? Common Causes and What to Do

Why Is My AC Blowing Warm Air?

There's nothing worse than turning on your air conditioner on a hot Albuquerque afternoon and getting hit with warm air. Before you panic, know that many of the causes are fixable — and some you can troubleshoot yourself before calling a technician.

At MGP Mechanical, we get this call all the time, especially once temperatures start climbing into the 90s. Here are the most common reasons your AC might be blowing warm air and what you can do about each one.

Check Your Thermostat First

It sounds obvious, but the thermostat is the first thing to check. Make sure it's set to COOL (not HEAT or FAN ONLY) and that the temperature is set below the current room temperature. If your thermostat runs on batteries, replace them. A thermostat with dead batteries or incorrect settings is one of the most common reasons for a service call that turns out to be a simple fix.

If you have a programmable or smart thermostat, check that the schedule hasn't reverted to a default setting.

Dirty Air Filter

A clogged air filter restricts airflow to the point where your system can't cool properly. In Albuquerque's dusty environment, filters get dirty faster than in other parts of the country. If you haven't changed your filter in the last 30 to 60 days, that's likely contributing to the problem.

Pull out the filter and hold it up to the light. If you can't see through it, replace it immediately. This alone can restore cooling in many cases.

Frozen Evaporator Coil

If your AC has been running but not cooling, you might have a frozen evaporator coil. This happens when airflow is restricted (usually from a dirty filter or blocked vents) or when refrigerant levels are low. You might notice ice on the refrigerant lines going to the outdoor unit.

If you suspect a frozen coil, turn the system off and let it thaw for a few hours. Check your filter and make sure all vents are open. If it freezes again after restarting, call a technician — you likely have a refrigerant issue.

Low Refrigerant

Your AC doesn't "use up" refrigerant like gas in a car. If levels are low, it means there's a leak somewhere in the system. Low refrigerant reduces your system's ability to absorb heat from your home's air, resulting in warm air from the vents.

This is not a DIY fix. A licensed technician needs to find and repair the leak, then recharge the system with the correct amount of refrigerant. At MGP Mechanical, we use electronic leak detection to pinpoint the problem accurately.

Dirty Condenser Coils

The outdoor unit (condenser) releases heat from your home to the outside air. If the coils are covered in dirt, dust, or cottonwood fluff — all common in Albuquerque — the unit can't release heat effectively. Your system works harder but produces less cooling.

You can gently rinse the outdoor unit with a garden hose (from the inside out) to remove debris. Make sure the unit has at least two feet of clearance on all sides. If it's heavily caked, a professional coil cleaning may be needed.

Tripped Circuit Breaker

Your AC system has two components — the indoor air handler and the outdoor condenser — and they're often on separate breakers. If the outdoor unit's breaker has tripped, the indoor fan will still blow air, but it won't be cooled.

Check your electrical panel for any tripped breakers. If the breaker trips again after you reset it, don't keep resetting it — call a technician, as this can indicate an electrical problem.

Aging System

If your AC is 10 to 15 years old and struggling to keep up, it may be losing efficiency. Components wear out over time, and older systems use R-22 refrigerant (Freon), which has been phased out and is extremely expensive to replace.

If your system is in this age range and needs frequent repairs, it might be more cost-effective to upgrade to a new, energy-efficient system. Newer units can reduce cooling costs by 20 to 40 percent, and there are rebates available through PNM for qualifying equipment.

When to Call a Professional

If you've checked the thermostat, replaced the filter, and ensured the outdoor unit is clear but you're still getting warm air, it's time to call in a pro. Issues like refrigerant leaks, electrical problems, and compressor failure require professional diagnosis and repair.

At MGP Mechanical, we offer same-day AC service calls throughout the Albuquerque metro area. We'll diagnose the problem, explain your options, and get your cooling back on track. Call us at (505) 878-5788 to schedule service.