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Why Does My AC Unit Keep Freezing Up?

This is a common problem, and often homeowners don’t realize it can be harmful to your air conditioner. If your unit is freezing up, it needs to be serviced. There are a few main causes:

6 Possible Reasons Your AC Unit Is Freezing Up

1. Your Air Filter Is Extremely Dirty

graphic that reads "why does my AC unit keep freezing up?" with the Harris Air Services logo in the bottom right cornerIf you suspect this is the problem, turn off your system. Don’t make the mistake of changing the air filter and turning the unit right back on. If you have seen ice, it will take four to eight hours to completely thaw.

If the air filter was the issue, and it’s not thawed out, the unit will continue to freeze. Just because ice has melted on the outdoor unit doesn’t mean the machine has thawed. The ice starts in the evaporator coil (in your attic) and then travels down the refrigerant lines to the outdoor unit.

You can’t see your evaporator coil, as it’s inside the indoor unit. If there’s ice outside, the evaporator is a complete block of ice inside.

2. Stuck Contactor in the Outside Unit

This can happen when it becomes “pitted” due to usage and age. It can weld itself together, and the outdoor unit never stops running. When the indoor unit stops running, the system will immediately start to freeze because there’s no airflow.

Contactors are like spark plugs on cars, they don’t last forever. We check contactors on our AC tune-up and maintenance visits. If they’re showing signs of wear, we suggest replacing the part.

3. Failed Indoor Blower Motor

If the blower fails, there’s no airflow. Many things can cause the motor to stop working. Sometimes it’s the motor itself, and other times there’s something that’s causing it not to run. Turn off your unit and call for AC repair immediately.

4. Low Refrigerant (Freon) Charge

This requires a qualified technician to diagnose. If your air conditioning system is low on charge, there’s a good possibility it’s leaking. A technician can check for a leak and help with a solution.

5. Bad Thermostat

If the thermostat control isn’t sending the correct signals to the indoor and outdoor unit, it can result in your AC freezing up. Call for service and have a technician figure out what’s going wrong.

6. Some Sort of Airflow Restriction

Possibly some insulation is loose somewhere in the system. A service person would need to take apart the indoor unit to diagnose if that’s the problem.

Count on Harris Air Services for Expert AC Troubleshooting

This list is limited but covers the most common situations that could make your AC system freeze up.

Call Harris Air Services today at 469-325-1034 if you’re noticing any of these issues.

Harris Air Services is ready to help! Learn more

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