Why is my AC coil frozen?

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Frozen AC coil

Frozen AC coil in Altamonte Springs

Restricted airflow is the most common cause by far — a dirty filter, a closed or blocked return, or crushed attic ductwork starving the coil of the air it needs to stay above freezing. Low refrigerant from a leak is the second most common. Either way, switch the system to fan-only and let the ice melt before anyone touches it.

What is most likely wrong

Ranked by probability

Likely causes, ranked by how often they turn out to be the answer
Cause	How common	What it looks like
1. Restricted airflow (dirty filter, blocked return, crushed duct)	Most common	Ice on the indoor coil or the line set; weak airflow at the registers even before it froze.
2. Low refrigerant charge from a leak	Common	System has been topped up before, or ran fine for a long stretch and then gradually lost cooling before icing.
3. Failing blower motor	Less common	Airflow feels weak at every register, not just some, and has been getting worse over weeks.
4. Dirty evaporator coil	Less common, usually paired with the above	Reduced cooling that has crept up gradually, often alongside a system overdue for a filter change or a service.

What you can safely check yourself

Before you call

Switch the thermostat to fan-only (not off) as soon as you see ice, and leave it there for a few hours to thaw fully before anyone diagnoses it running.
Check and replace the filter — a clogged filter is the single most common cause of a frozen coil.
Confirm every supply register is open and every return is unobstructed by furniture or a closed door.
Never top up refrigerant yourself, and do not let anyone top it up without finding the leak first — refrigerant is not consumed, so low charge means it leaked out somewhere.

Where the licensed line is

A run capacitor holds a lethal charge even after the power is off. Refrigerant handling requires EPA Section 608 technician certification, and in Florida this work requires a state-licensed air conditioning contractor under Chapter 489, F.S.

Verify the licence of any contractor you hire at the DBPR licensee search.

Why this happens in Altamonte Springs

Local pattern

In this city's smallest attached units — Sandy Cove runs a 633 sq ft median, for instance — the air handler sits on a closet or wall with very little clearance, and the return grille is often undersized for the equipment behind it. That is a straightforward airflow restriction, and it freezes a coil exactly the same way a dirty filter does.

In a detached house on the original 1970s or 1980s attic duct, a section of flex duct that has sagged or been crushed underfoot during an attic repair has the same effect: airflow drops below what the coil needs.

Seminole County Property Appraiser CAMA extract (Parcels.csv, 5 September 2026), tax district A1 — Altamonte Springs. 13,253 improved residential parcels: single-family, townhome and condominium. Apartments and manufactured homes excluded. Per-subdivision figures are the 20 largest platted communities in tax district A1 from the same extract.

What the fix typically costs

Researched ranges

Researched Orlando-market ranges, September 2026. Not this business's prices.
What is being priced	Researched range	What moves it
Diagnostic to find the actual restriction	$75–$150	Orlando-market diagnostic or dispatch fee. After-hours calls commonly $150–$250.
Refrigerant leak repair and recharge, if that is the cause	$400–$1,600	Refrigerant leak repair and recharge, Orlando market. A leak search alone commonly adds two to four hours over a straight recharge.
Blower motor	$450–$900	Air handler blower motor, Orlando market; variable-speed/ECM motors sit at the top of the range. A Central Florida contractor's own published price runs $400–$800.
Evaporator coil	$1,500–$2,500	Evaporator coil, Orlando market, parts and labour.

Sources: Smart Home Air & Heat, Orlando repair-cost ranges (August 2026), Clear Comfort Orlando's own published prices, and for the expansion valve the Angi Orlando aggregator estimate (May 2026), the only source found for that part. Compiled September 2026. Not this business's prices.

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