Goodman AC Not Cooling: Fixing The Infamous Frozen Evaporator Coil

 

Goodman central air conditioners are the absolute workhorses of suburban America due to their affordable price point and readily available mechanical parts. However, when a Goodman system faces heavy thermal loads in mid-summer, a very common diagnostic failure occurs: the indoor evaporator coil transforms into a solid block of ice, causing the system to blow hot air through the supply vents.

If you see ice forming on the copper lines outside or water dripping through your ceiling from the indoor air handler unit, follow this technical protocol to restore cooling performance.

1. Step One: The Forced Thermal Thaw

Never attempt to scrape or pick ice off the delicate aluminum fins of a Goodman evaporator coil. You will puncture the copper lines, causing a total loss of expensive R-410A refrigerant.

 The Procedure: Go to your digital thermostat. Flip the system setting from "COOL" to "OFF". Then, switch the fan setting from "AUTO" to "ON". This keeps the indoor blower motor running continuously while keeping the outdoor compressor deactivated. The warm house air passing over the coil will safely melt the ice block within 2 to 4 hours. Ensure your condensate drain pan line isn't clogged, or the melting ice will flood your mechanical closet.

2. Step Two: Airflow Suffocation Diagnostics

Once the ice has completely converted back into water, you must figure out why the low-temperature liquid refrigerant inside the coil dropped below freezing (32^{\circ}F / 0^{\circ}C). Airflow is the number one suspect.

 

The Issue: If the indoor fan cannot push enough warm house air across the evaporator coil, the boiling refrigerant doesn't absorb enough heat. Its temperature plummets, causing the condensation on the outside of the fins to instantly freeze into ice.

 The Fix: Check all supply registers and return air grilles in the house. Ensure the homeowner hasn't closed off more than 20% of the basement vents to "save energy"—this chokes the system. Inspect the blower wheel inside the Goodman furnace or air handler. If the curved blades are caked in grease and dust, the fan cannot move the required 400 Cubic Feet per Minute (CFM) of air per ton of cooling capacity. Clean the blades using a wire brush.

3. Step Three: The Liquid Line Temperature Test (Low Refrigerant)

 

The Issue: If your air filters are brand new and the fan is blowing strong but the Goodman coil freezes again within an hour, the system is low on refrigerant due to a slow pinhole leak. When a system is undercharged, the pressure drops inside the evaporator, lowering the boiling point of the R-410A below the freezing mark.

 

The Fix: Touch the insulated, thicker copper suction line entering the indoor unit. It should feel ice-cold and sweaty, like a fresh can of soda. If it is dry and barely cool, and the thin uninsulated liquid line is warm or room temperature, the system requires a professional EPA-certified technician to locate the refrigerant leak, braze the copper fracture, and recharge the system.