Frozen AC Evaporator Coils: Causes & Troubleshooting Tips

By Fix4U Team
Air Conditioners, Appliances

Imagine it’s the peak of summer, you flip the AC on high, and icy cold air starts blowing from the vents. But within minutes, the airflow slows to a trickle and chilly breezes turn lukewarm. You likely have frozen AC evaporator coils cripping cooling.

While this is a relatively common air conditioner issue, frozen evaporator coils are easily prevented through proper maintenance. This AC troubleshooting guide from Fix4U Repairs will cover what causes coils to freeze and tips to safely thaw and restore cooling.

How Do AC Evaporator Coils Work?

To understand frozen coil causes, you need to know evaporator coil operation:

  • Evaporator coils are located inside the central air handler or furnace system.
  • As warm indoor air blows across the coils, liquid refrigerant inside evaporates and pulls heat out of the air.
  • This cools the air before it circulates through ductwork into your home.
  • Refrigerant absorbs lots of heat as it evaporates into a gas within the coils.
  • The refrigerant gas gets sucked into the compressor to repeat the cooling cycle.

For proper cooling, refrigerant needs to evenly evaporate across entire evaporator coil surfaces.

What Causes Frozen Evaporator Coils?

AC evaporator coils mainly freeze up when:

  • Low Refrigerant Levels: Not enough refrigerant flowing through coils allows moisture to freeze on coil surfaces. Slow leaks are the most common cause of low refrigerant.
  • Dirty Air Filter: A clogged filter restricts airflow over coils. This disables heat absorption allowing ice buildup in areas with reduced airflow.
  • Restricted Vents: Like a dirty filter, any blockages in vent ductwork restrict target airflow over coils leading to partial freezing in low airflow areas.
  • Overcharged Refrigerant: Too much refrigerant floods the evaporator coils allowing liquid refrigerant to freeze on coil surfaces.
  • Faulty Components: Issues with parts like blower motors, valves, and sensors can disrupt refrigerant flow and lead to freezing.
  • Outside Ambient Temperature: Extremely hot outdoor temps paired with very cold indoor settings can overwhelm AC capacity and cause freezing.

Signs of Frozen Evaporator Coils

Fix4U Repairs' Technicians Fixing Frozen Ac Evaporator Coils  Problem In Gta

Watch for these symptoms that indicate frozen AC evaporator coils:

  • Reduced airflow from vents
  • AC system freezing up and icing over
  • AC still running but not cooling properly
  • Higher humidity in home from restricted airflow
  • Frost buildup on suction line entering evaporator
  • Ice formation on exterior of evaporator case
  • Frozen drip tube draining evaporator coils

Thawing & Troubleshooting Frozen AC Coils

Follow these steps to safely thaw frozen AC evaporator coils:

  • Turn Off AC Unit: As soon as airflow drops or coils start icing over, shut off the AC unit at breaker or switch. Thawing happens faster with the system off.
  • Remove FilterTake out the air filter to allow maximum air circulation across coils during thaw.
  • Turn on Fan: Turn on just the blower fan to blow warm indoor air over coils and speed thawing. Point a fan directly at coils.
  • Wait for Full Thaw: It may take a few hours to overnight for frozen coils to fully defrost. Confirm no ice remains before restarting system.
  • Check Refrigerant Level: Use gauges to check refrigerant pressures. Recharge system if low levels caused freezing.
  • Inspect Components: Check filter, blower motor, valves and thermostats for issues contributing to low airflow or refrigerant flow.
  • Adjust Thermostat: Lower indoor setting and raise outdoor unit a few degrees to reduce likelihood of freezing.
  • Replace Filter: Install a clean filter to restore proper airflow across evaporator coils.
  • Monitor Operation: Run system to verify normal, condensation-free cooling before leaving the AC unattended again.

Frozen AC coils? Call Now To Fix Your AC!

Preventing Frozen Evaporator Coils

Routine maintenance prevents freezing issues:

  • Change filters monthly during peak AC season for maximum airflow.
  • Have a technician annually check refrigerant levels and system components.
  • Keep outdoor AC unit clear of debris that could restrict airflow.
  • Have evaporator coils professionally cleaned to prevent buildup.
  • Set indoor temp 2-3° higher than normal if freezing continues despite above steps.

Don’t get caught without comfortable cooling – schedule service today with the AC experts at Fix4U Repairs! We offer complete maintenance plans to keep your system running right.

(647) 363-5205

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