Finding ice on your indoor AC unit or copper lines in Texas summer feels alarming — and it is a real problem, even if the cause is often straightforward. Here's the exact sequence of what to do when you find ice inside your AC system.
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Turn thermostat to FAN ONLY. Not OFF (that stops the thaw). Not COOL (makes it worse). FAN ONLY runs the blower to circulate warm room air across the coil, melting the ice. This takes 2–4 hours. Skipping this step and jumping to repairs doesn't work — you can't access the coil while it's iced.
💰 Cost: Switch to FAN ONLY right now
A severely clogged filter is the #1 cause of indoor icing. Restricted airflow causes the coil temperature to drop below 32°F. While the coil thaws, pull the filter and check it. If it's gray, packed, or visibly clogged — you likely found the cause.
💰 Cost: Replace filter while coil thaws
After the coil is fully thawed (2–4 hours) and the filter is replaced, switch back to COOL and monitor for 30 minutes. If the system runs normally and the house cools — filter was the cause, problem solved. If ice forms again within a few hours — there's an underlying issue beyond the filter.
💰 Cost: Monitor for 30 min after restart
Ice that returns after filter replacement means the coil temperature is dropping below freezing from an internal cause — almost always low refrigerant. Low refrigerant pressure causes the refrigerant to expand more than designed, dropping coil temperature below 32°F. Requires a licensed technician.
💰 Cost: If ice returns: call for refrigerant diagnosis
A significant ice event can produce 1–5 gallons of water when it melts. Check around and below the air handler for water staining, soft drywall, or moisture in adjacent materials. Water damage that goes undetected leads to mold.
💰 Cost: Inspect area around air handler after thaw
AC systems ice up when the evaporator coil temperature drops below 32°F. This happens from two main causes: restricted airflow (usually a clogged filter) that prevents warm air from moving across the coil, or low refrigerant that causes the refrigerant to expand more than designed and drop the coil below freezing.
Switch the thermostat to FAN ONLY immediately. Replace the air filter while waiting for the coil to thaw (takes 2–4 hours). After full thaw, restart in COOL mode and monitor. If ice returns within a few hours, you have a refrigerant issue — call for professional diagnosis.
No — running in cooling mode while frozen risks cracking the evaporator coil and damaging the compressor. Switch to FAN ONLY to thaw. This is not optional — the damage from running a frozen AC is expensive.
Replace air filters every 3–4 weeks in summer. Keep all supply vents open and unobstructed. Schedule annual maintenance including refrigerant level check and coil cleaning. A system that ices up regularly with a clean filter has a refrigerant or airflow issue that needs professional attention.
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"Found the issue fast and fixed it same day. Honest diagnosis, no upselling. Exactly what you want when your AC goes out in July."— Spring TX homeowner, 77386
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1827 Riley Fuzzel Rd Suite C, Spring, TX 77386
Serving Harmony, Benders Landing, Legends Ranch, Imperial Oaks, Spring Trails, The Woodlands.
19507 Wied Rd Suite B, Spring, TX 77388
Serving Klein, Champion Forest, Vintage Park, Gleannloch Farms, Tomball, Cypress.
AC Repair Expo Heating & Cooling Inc — same-day diagnosis and repair across Spring TX, The Woodlands, Tomball, Klein, and North Houston. Honest diagnosis, fair pricing, licensed TACLB43277C.
Riley Fuzzel Rd: 1827 Riley Fuzzel Rd Suite C, Spring TX 77386 · Wied Rd: 19507 Wied Rd Suite B, Spring TX 77388
