One moment, you're basking in the awesome comfort of your air conditioning system. The next, you're wondering why the inside of your A/C unit looks like the inside of your freezer. It's not uncommon for hard-working A/C units to suffer from heavy frost or ice buildup, but the end result can leave you sweating on the hottest of days. Read on to learn the causes of a frozen A/C system and how you can fix it.
What Causes Frozen A/C Units
During your air conditioner's normal operation, temperatures at the evaporator coil's surface hover at just above the freezing point thanks to the constant influx of warm indoor air over the coil. If anything slows down or stops that airflow, coil temperatures can drop below freezing and cause ice to form on the coil surface. Depending on the amount of humidity in the air, ice continues to build up until the coils are completely blocked.
Any one of the issues mentioned below can cause your A/C system to freeze over:
- Dirty A/C air filter – A clogged air filer can block airflow to the coil, thus setting the stage for a frozen coil.
- Dirty evaporator coil – Dust and dirt buildup on the coil itself can stymie airflow and cause ice buildup.
- Closed or blocked registers – Too many closed or blocked registers can throw the A/C system's airflow out of balance, resulting in poor airflow and subsequent coil freezing.
- Low refrigerant – Low refrigerant levels can cause the A/C system to operate with too little pressure, resulting in frozen coils and refrigerant lines.
How to Unfreeze Your A/C
Start by switching your A/C unit's thermostat setting from "COOL" to "FAN". The idea here is to run the air conditioner's blower fan to push air across the frozen coils. The warm air will help the coil thaw out and the resulting runoff will land harmlessly in the condensate drain pan, where it'll eventually drain out of the unit. Keep an eye on the drain pan from time to time, just in case it overflows due to the unusually high volume of runoff passing through.
You can run your A/C system again once it's thawed, but you're still left with tackling the underlying causes of your unit's freeze-up. Some of these issues you can handle on your own, but in the case of low refrigerant levels or a malfunctioning blower fan, you're better off letting an HVAC contractor take care of the problem.