Why is My AC Blowing Hot Air?

Experiencing AC blowing hot air? Discover possible reasons why AC blows hot air. Get expert help at Sandium to resolve issues and restore AC hot air to your system.

Updated on Oct 22, 2023
5 min read
Why is My AC Blowing Hot Air?

An air conditioner blows warm air when the cooling mechanism is not working and the fan is operating. There are several things that can cause this. This guide will talk about the more common issues undermining your comfort in the Bay Area.

1. Thermostat Troubles

Whenever you are worried about your AC, the first thing you should check out is the thermostat. Somebody in your home may have tampered with the settings accidentally. The thermostat should be set to ‘cool’ with the fan on ‘auto’. Don’t forget to look at the temperature settings. It should be lower than room temperature.

2. Clogged Air Filter

Maybe your air conditioner is just not getting enough air. The system needs warm air to flow over the coils to function properly. An air conditioner’s filter is designed to keep out contaminants and dust from the system. However, when it gets clogged, it is unable to allow air to pass through. Without air on the coils, the fan keeps blowing back air in the room. You should check the air filter if you have not had the air conditioner maintained in a while.

3. Closed or Blocked Return Vents

It is possible the vent grilles were never opened after the winter. It is common for people to accidentally block the vents with furniture and other obstructions as well. Make sure all returns and registers are open to allow air to freely circulate.

4. Leaky or Disconnected Ducts

You may have air flow problems unseen to you in the ducts. Your ductwork may have cracks, holes or be completely disconnected. This will prevent return air from making its way to the unit. This may also cause cooled supply air to get wasted on walls, in crawl space and attic. You should take a look if the ducts are accessible. It is common for damage to occur because of rodents, birds, or construction projects.

5. Outdoor Unit Has No Power

There is an indoor air handler unit and an outdoor condensing unit in most air conditioning systems. Your system will blow air if the fan is working fine. However, there will be no cooling if the condenser is not working as it should, causing the AC to blow warm air. This can happen when the condenser doesn’t have power because of a tripped circuit breaker or a blown fuse.

You should note that this is an electrical issue and you shouldn’t try to diagnose this on your own unless you are an HVAC expert or a trained electrician. Live voltage is not something for amateurs to experiment with. However, you can always check the emergency shutoff switch.

6. Condenser Coil is Dirty

Releasing heat outside the building is an important function of the condenser unit. Your condenser coil is responsible for this. But, it may get caked with grime, dirt, leaves, and trash. This can impede the operation of the coils. Your system may not cool effectively because of this, causing the air conditioner to blow warm air.

7. Leaking Refrigerant

Refrigerant is present in a closed loop to cool air. Leak in the coils or the refrigerant lines can cause the system to lose cooling power. This can happen at once or gradually over a period of time depending on the size of the leak.

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