Frozen AC coil in Casselberry, Florida
Ice on the indoor coil or the copper suction line means the coil is running below freezing, and there are only two root causes: not enough air over the coil, or not enough refrigerant in it. Turn the cooling off, leave the fan on, and let it thaw before anyone diagnoses it.
What is most likely wrong
| # | Cause | How common | What it looks like |
|---|---|---|---|
| 1 | Blocked or excessively restrictive filter | Very common | Not enough air across the coil. The most common cause by a wide margin. |
| 2 | Dirty evaporator coil | Very common | Same effect as a blocked filter, and usually the consequence of years of them. |
| 3 | Low refrigerant charge from a leak | Common | Ice starting at the metering device and spreading along the suction line. |
| 4 | Failed or failing blower motor | Common | Airflow drops without the filter being dirty. |
| 5 | Closed, blocked or crushed return path | Common | Furniture over a return grille, or crushed return flex. |
| 6 | Running the system below about 60°F outdoors | Less common | Uncommon here, but it happens on cool nights with a thermostat left low. |
| 7 | Wrong metering device or a mismatched coil | Less common | Usually traceable to a changeout done without a matched system. |
What you can safely check yourself
- Turn the cooling off at the thermostat and set the fan to on. That thaws the coil with air instead of heat. Do not chip at ice and do not run a hair dryer near a coil.
- Expect one to three hours of thawing, and put towels down — a thawing coil produces a lot of water quickly and can overwhelm a drain pan.
- Replace the filter while it thaws.
- Check every supply and return grille is open and unobstructed.
- Once thawed, run it and watch. If it ices up again within a day, it is a charge or airflow fault, not a one-off.
Refrigerant, capacitors and the inside of an electrical panel are not homeowner jobs.
A run capacitor holds a lethal voltage after the disconnect is pulled. Refrigerant handling requires EPA Section 608 certification. And in Florida the work itself is regulated: an air conditioning contractor licensed under Chapter 489 may replace, disconnect and reconnect the power wiring at the dedicated disconnect, and repair or replace disconnects, breakers and fuses on dedicated HVAC circuits — s. 489.105(3). That scope exists precisely because this work is not general-purpose electrical work.
Verify any Florida licence, including ours, at the DBPR licensee search.
Why this happens in this housing stock
Freezing is an airflow disease, and Casselberry has an airflow problem baked into its housing stock. The median improved residential parcel dates from 1977 and 57.1% of the city was built between 1970 and 1989 — an era that commonly built a single undersized central return. Add a dense high-MERV filter to a duct system already near its static pressure limit and the coil freezes; the homeowner has done everything the filter packet told them to do.
That is why the answer to repeated freezing in an older Casselberry house is usually more filter area rather than a better filter — a 4- or 5-inch media cabinet, or a second return. Filters and the MERV trap, and how to have the ducts measured.
The humidity angle matters too. In a latent-load climate a coil that ices is not just failing to cool, it is dumping the water it has already condensed back into the drain pan in a rush when it thaws, which is a common route to water where it should not be.
Seminole County Property Appraiser CAMA extract (Parcels.csv, dated 2026-09-05). Improved residential parcels — single-family, townhome and condominium — in city tax district C1, City of Casselberry. n = 8,563.
What the fix typically costs
| Job | Researched range | What drives it |
|---|---|---|
| Diagnostic visit | $75–$150 | Ask for a static pressure reading with it. |
| Evaporator coil cleaning or replacement | $700–$2,500+ | Cleaning at the bottom, replacement at the top. |
| Refrigerant leak repair | $200–$1,500+ | Finding the leak is most of the cost. |
| Blower motor | $300–$800 | ECM at the top of the band. |
| Duct repairs or replacement | $1,500–$5,000 | If the return path is the root cause. |
These are researched market ranges, not our prices and not a quote.
The dollar figures below come from published third-party cost guides — named and linked at the foot of the page — and from the City of Casselberry’s own published permit fee. They are here so you can tell whether a quote you have been handed is in the ordinary range for this work. They are not an offer, and no two houses in Casselberry cost the same to do.
Coil iced up again after thawing?
That is a charge or airflow fault, not bad luck. Worth a measurement rather than another filter.
Phone: (689) 308-3675 · Monday-Friday, 8:00 AM - 5:00 PM
Where the facts on this page come from
Every figure above is either a primary-source document or a named third-party cost guide. All of it was checked in September 2026. Fee schedules, rebate amounts and market prices change without notice — if you are about to spend money on one of these numbers, open the source and check it.