Why Is My AC Blowing Hot Air? A Portland Tech Explains

Why is my ac blowing hot air

An AC that’s blowing hot air is one of the most common HVAC problems in Portland.

The five most typical causes for your AC blowing hot air include:

  • Wrong thermostat settings
  • The outside unit is suffocated
  • A clogged air filter
  • A refrigerant leak
  • A tripped circuit breaker/wiring issues

We will dive into what DIY solutions are available for the above AC issues and which issues require professional help.


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AC Issue #1: Thermostat is set to HEAT or fan is set to ON

Thermostat FAN and HEAT settings depicted

Thermostat FAN and HEAT settings depicted

If your AC thermostat is set to HEAT and/or your fan is set to ON, your AC will blow hot air. In this case, double-checking that your thermostat is correctly adjusted is an easy way to fix your AC issue.

DIY Solution for Thermostat Settings:

First, make sure your thermostat isn’t set to HEAT.

Next, we want to check the fan’s setting. The fan controls the AC blower which vents air throughout your home. You want to make sure the fan is set to AUTO instead of ON.

When the fan is set to AUTO, your AC’s fan will only blow during a cooling cycle (i.e. when the air is being cooled). However, when the fan is set to ON, the fan will blow 24/7 and push air through your home regardless if the air is cool which explains why you might feel warm air from your vents sometimes.

Also, go ahead and check if your thermostat batteries are old and replace them if necessary.

Professional Solution for Thermostat Settings:

If you’ve followed the above steps and you’re still having issues, you might have a problem with your thermostat’s wiring. It’s recommended — unless you have wiring experience — that you contact an HVAC professional to repair the wiring in your thermostat or replace your thermostat if needed.

AC Issue #2: A suffocated outside unit

Dirty outdoor AC unit

Leaves and twigs in the outside unit

Your AC’s outside unit (AKA the condenser) will block cold air from circulating throughout your home if it’s:

  • Covered with dirt and leaves
  • Clean but shrubbery or debris is too close to its perimeter
  • Covered by a decorative cover

Think of your outside AC unit as a dragon — it’s constantly blowing out hot air. The outside unit’s job is to dump all the heat it collects from inside your home outdoors.

Now, if your outside unit doesn’t have adequate “breathing space” to dump out all of that hot air, it will send the hot air back into your home.

DIY Solution for Suffocated Outside Units:

You can get rid of any leaves and dirt stuck on the unit by gently cleaning the outside unit with a garden hose set on low flow. Home supply shops also sell coil cleaners if you want a deeper clean.

Also, remove any decorative covers that are on the outside unit to ensure the unit has enough room to “breathe out” hot air. Likewise, any shrubbery or fencing closer than 2 feet around the outside unit will suffocate it and not give it enough space to dump out the heat.

Professional Solution for Suffocated Outside Units:

Scheduling professional AC maintenance twice a year is great for preventing your outside unit from being suffocated with dirt, leaves or debris. During a maintenance visit, a tech will thoroughly wash your outside unit’s internal and external components to get rid of any grime that could suffocate it.

A side benefit is that annual AC tune-ups also maintain your manufacturer’s warranty. Manufacturers can void your warranty if you don’t have your AC professionally serviced at least once a year.

Professionally-maintained AC units are also less likely to have issues in the summer when you need cold air the most. It’s the same idea as having your car’s oil changed every 3-6k miles to prevent your car from breaking down in a dire situation.

Contact a Portland HVAC professional to have your AC serviced annually.

AC Issue #3: A clogged air filter

Clean air filter versus clogged air filter

Clean air filter versus clogged air filter

If your AC system’s filter is clogged, it will limit the amount of cool air the system can produce. Plus, if the clogged filter isn’t changed for some time, it will eventually lead to more costly problems like compressor failure. In both cases, a clogged filter can cause your AC to blow lukewarm and/or hot air.

In contrast, a clean air filter allows for warm air to enter your AC system to be chilled and for the chilled air to leave your AC system. Therefore, a clean filter will push enough cold air out into your home to match your desired temperature.

DIY Solution for Clogged Air Filters:

Replace your clogged air filter to allow cool air to freely flow out of your unit. If you have a standard fiberglass air filter (it will have a cardboard frame and paper/mesh surface), you will need to replace your air filter every couple of months.

How do I change out my clogged fiberglass air filter?

  1. Turn off the AC system at the unit-level AND turn off the circuit breaker.
  2. Pull your dirty air filter out of the insertion slots.
  3. Check what size your air filter is and buy a replacement: You can figure out your air filter’s size by referring to the label on the side of the air filter. If the label doesn’t say the size, you can refer to your owner’s manual or bust out a measuring tape.
  4. Insert the new air filter. Make sure the arrows on the new filter point towards the blower. This is important because an air filter installed in the wrong direction will make your AC work harder.

Professional Solution for Clogged Air Filters:

Replacing a dirty air filter is a simple DIY solution.

The scenarios in which you would bring in a professional for clogged air filters is if:

  • You need help replacing your air filter. Some air filters are in the AC vents. The location makes the filters hard-to-reach and dangerous to replace. Contact a professional to have the air filter cleaned.
  • You have a high-MERV filter: MERV (Minimum Efficiency Reporting Value) represents how well an air filter catches superfine airborne particles. The higher the MERV, the better the air filter is at its job. Unfortunately, since the high-MERV filter catches more particles, it also clogs more easily. A high-MERV filter may require a professional for replacements since these filters are more complex (and aren’t always sold at common home improvement stores).
  • The dirty air filter makes your evaporator coils dirty too. When warm air is blown over dirty evaporator coils, the dirty coils can’t cool the air as efficiently as they would if they were clean. A professional would need to clean the coils so the AC blows cold air again.

AC Issue #4: Low on refrigerant/refrigerant leak

A refrigerant line

A refrigerant line

Refrigerant is a chemical liquid that cools the warm air entering your AC. When refrigerant levels are low, the AC can’t cool the air efficiently and will eventually circulate hot air.

Some signs that your AC’s refrigerant levels are low are:

  • Ice forming on your inside and outside units
  • AC blows hot air in the daytime but cold air at night
  • Hissing or bubbling noises near the AC

Professional Solution for Low Refrigerant/Refrigerant Leaks:

If you notice any of the above signs of low refrigerant levels, you have a refrigerant leak. Refrigerant works in a circular loop so the amount should never decrease.

Now that you know you have a refrigerant leak, you should absolutely contact a professional. There is no DIY solution for this problem since refrigerant is toxic to humans and should only be handled by licensed professionals. The tech can assess the leak site for the best solution. If vital parts of your AC are damaged or your AC uses an outdated, hazardous refrigerant (i.e. R-22 refrigerant), you may have to replace your entire AC system.

For refrigerant leaks that don’t require a whole system overhaul, an HVAC technician will:

  1. Find the leak
  2. Repair and seal the leak
  3. Add back refrigerant to the appropriate level for your AC

You want to find a technician that will fix the leak first. If a tech suggests refilling the refrigerant without checking for and/or repairing the leak itself, they’re angling to get you to pay for a refrigerant refill down the line and you need to find a different technician.

AC Issue #5: Tripped circuit breaker/wiring issues

Circuit breaker for the AC

Your AC cannot effectively cool your home if your outside unit’s circuit breaker trips (i.e. goes into neutral position).

Most homeowners don’t realize that their AC has two different circuit breakers, one per unit. When the outside unit’s circuit breaker trips, the inside unit is still working and blowing air (it’ll just be hot air). If your inside unit’s circuit breaker trips, you won’t even be able to turn on your thermostat.

DIY Solution for Tripped Circuits:

Find your grey, metallic circuit breaker box. Most circuit breaker boxes live in the garage, basement, laundry room or on an external wall. You want to find the electrical panel and the switch labeled HVAC or AC. If your panel isn't labeled, look for a tripped switch.

How to Reset Your AC’s Circuit Breaker

Once you’ve found your tripped circuit, reset your AC’s circuit breaker:

  1. First, turn the circuit OFF (to the right)
  2. Then turn the circuit ON (to the left)
  3. Wait 30 minutes for the system to reset itself

Professional Solution for Tripped Circuits:

Call a professional ASAP if you run into situations like:

  • A fuse blowing soon after resetting
  • The circuit breaker not staying ON and tripping again

Do not reset your circuit more than once. If you overload the current, serious damage can occur to your home’s electrical wiring and a fire can start. A blown fuse or a circuit that trips over and over again indicates deeper wiring issues in your home.

Whether your AC problem is big or small, contact our experienced Portland technicians.

If your AC is blowing hot air, you could be dealing with other, more complex issues that require professional help, such as:

  • Compressor issues
  • Capacitor problems
  • Broken contactors
  • Leaky ducts

When your AC issue requires a professional or your DIY solution didn’t work, contact Four Seasons.

You’ll never need to sacrifice high-quality service for budget reasons when you choose Four Seasons. Not only do we provide the best prices because our efficient business practices allow us to pass huge savings to our customers, but we also train our techs to repair virtually every AC brand.

We will get your AC working again. Schedule an AC repair today by clicking below or calling us at 503-538-1950.

Apart from Portland, we also service Sherwood, Oregon City, Hillsboro and many other areas.

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