Why Is My AC Blowing Hot Air?

My AC unit is not cooling but blowing warm air. Now what?

Check to see if the condensing unit (outside unit) is running.

What is happening in the air handler (inside unit) is running, but the condenser is offline, (take a look), so there is no cooling. The air handler is only circulating warm air through the house.

It may even cause the house temperature to rise because if the ductwork is in the attic, the ductwork system can gain heat from the attic space and transfer to your living area.

1. Check the float switch

One of the most common reasons the condenser is not operating is the condensate overflow float switch has activated. This safety device literally "floats" in the water when the condensate drain has backed up with water.

Clearing the drain line to your HVAC system may resolve the issue. The float switch is located near the bottom of the air handler near the drain line. The most common float switch is white PVC with a round top.

There will be small black wiring going to it. You can pull this out and check for the presence of water. Be careful - if left out and drain line not cleared, water could overflow and cause damage.

If the air handler is located in attic space, there may be two switches.

One on the air handler, one in the secondary pan under air handler. If water is in the secondary pan, that's a sure sign water is not draining properly. This pan should always be dry. Remove water with a wet/dry vac. Clear drain line.

Float switch causes ac to to blow hot air

2. Check your condenser breaker.Check break causes ac to blow hot air

The condenser is on a separate electrical circuit from the air handler.

Check to see if the breaker has tripped or fuses have blown.

No power = no cooling.

3. Check your thermostat

Seems obvious, but we run multiple calls a year where the thermostat was incorrectly set.

Make sure the thermostat is set to "cool" and the fan is set to "auto" position.

AC is blowing hot air, but both units are running. Check this:

4. Check your condensing unit

The condensing unit has two refrigerant lines entering the unit. One is a small 3/8" (liquid line). The other is a larger 3/4" (suction line), and more typical size. Feel the suction line; it should be cold.

If it is not cold, the system may be low on refrigerant, or the compressor is not operating.

Why Is My AC Blowing Hot Air - condensorIf this is the case - shut the unit off to prevent possible damage.

If the suction line was cold, let's check the liquid line. If it feels hot, your condenser coil may be dirty.

The condenser rejects the heat out of the refrigerant. If it is dirty, the system loses capacity and can not cool as it should.

Try cleaning the condenser. Make sure you are careful not to damage the fin surface of the condenser; it could make the situation worse.

If your air conditioner has some age to it, the coil may be oxidized which also has the same effect, poor heat transfer- very inefficient. It might be time for a new system.

5. Air Filter dirty/evaporator coil dirty

Check your air filter, a dirty filter is restrictive and also reduces heat transfer. Change if needed.

If the evaporator coil is dirty - call a professional to clean. It will pay for itself in the efficiency you will gain from having a clean coil.

Why Is My AC Blowing Hot Air - Ductwork6. Ductwork Damaged.

It could be your air conditioner is performing normally, but your ductwork is in bad shape.

Your ductwork can be losing air in the attic or sucking in hot attic air. If the air conditioner is not cooling "suddenly."

Was there a serviceman or cable guy in your attic? They are notorious for damaging ductwork.

Just something to consider.

Looking for Professional Help?

Air Zero is here if you need us. We service the St. Petersburg Fl. Area, along with Largo, Seminole, and Clearwater, and all of Pinellas County. Give us a call at 727-392-6111.