What causes an A/C to freeze up usually lies in maintenance issues, like keeping the air filter clean and having the system routinely cleaned and adjusted by an HVAC contractor. It’s important to address a frozen A/C quickly, since it can drive up energy costs, stop cooling, create water damage when the frost melts, and harm the system’s compressor.
Lack of Airflow
When inadequate air blows over the evaporator coil inside the blower compartment, the coil can freeze. These conditions will reduce the amount of air going over the coil:
- Dirty air filter – The air filter traps airborne particulates before they enter the blower to keep the parts inside clean. When too much dust collects on it, airflow slows, which can freeze the coil over since it can’t absorb enough heat from the air. The refrigerant stays cold and the humidity in the air can freeze on the coil, instead of condensing and draining away.
- Dirty evaporator coil – Dust and mold are common causes of a freezing evaporator coil. If you’ve kept the air filter clean, you may have mold growing on the coil. The cool temperatures and moisture inside the cabinet can foster mold growth. If you can’t access the coil, an HVAC technician can inspect and clean the coil for you.
- Blower fan – If the blower fan isn’t moving enough air over the coil, it can freeze. The motor may need service or replacement if adjusting the settings doesn’t change the amount of air going through the system. This is something your HVAC contractor can help you determine.
If the air filter is clean and the airflow sufficient, the next most common trigger for what causes an A/C to freeze up is low refrigerant. An HVAC technician can measure the amount in the system and add more after identifying the cause.
If you’re trying to identify what causes an A/C to freeze up, the experts at Rodenhiser Plumbing, Heating & Air Conditioning can help you. We’ve been providing exceptional HVAC services for homeowners along the Route 495/128 area of Massachusetts since 1928.
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