AC running but not cooling in Casselberry, Florida

When the system runs continuously but the house never gets cool, the usual causes are a dirty condenser coil, low refrigerant, duct leakage into a hot attic, or a system that is simply undersized for the load it now faces. It is a capacity problem, not a power problem.

Diagnosis

What is most likely wrong

Likely causes, ordered by how often they turn out to be the answer
#	Cause	How common	What it looks like
1	Dirty or blocked condenser coil	Very common	Outdoor unit running hard, the air off the top of it barely warm, long run times.
2	Duct leakage or crushed flex in the attic	Very common	One or two rooms far worse than the rest; the system never satisfies.
3	Low refrigerant charge from a leak	Common	Gradual decline over weeks. Ice at the evaporator or on the suction line in bad cases.
4	Dirty evaporator coil	Common	Weak airflow at every vent even with a new filter.
5	Failing capacitor or compressor running weak	Common	Long cycles, high bill, some cooling but never enough.
6	Undersized or wrongly matched equipment	Less common	Never keeps up on the hottest afternoons but is fine in April. Often a system replaced without a load calculation.
7	Strip heat energised alongside cooling	Less common	A miswired changeout. Rare, expensive on the bill, and it feels exactly like this.

Before you call

What you can safely check yourself

Filter first, always.
Look at the outdoor coil: if you cannot see daylight through the fins, it is blocked. Rinse it from the inside out with the power off.
Check nothing is crowding the condenser — a fence, a hedge or a screen enclosure too close raises head pressure.
Feel the two copper lines at the condenser: the large insulated one should be cold and sweating, the small one warm. Both warm suggests a charge problem.
Walk the vents. If one room is dramatically worse, it is a distribution problem, not a capacity one.
Check the attic access for obviously crushed or disconnected flex duct — from the hatch, not by crawling across a 130°F attic.

Where the licensed line is

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.

In Casselberry

Why this happens in this housing stock

This is the symptom that most often turns out to be ductwork rather than equipment, and Casselberry is a ductwork city. 57.1% of its 8,563 improved residential parcels were built between 1970 and 1989 and the median build year is 1977. The equipment in those houses has been replaced three or four times; the attic trunk very often has not.

What that produces is precisely this complaint: a modern system that runs and runs, cannot move its rated airflow through a restricted duct system, and therefore never delivers its rated capacity whatever the SEER2 sticker says. Duke Energy will pay 50% of the cost of a duct test plus up to $200 toward repairs, after the free Home Energy Check — which is the cheapest way to settle the question. Test rather than inspect.

The other local suspect is sizing. A rule-of-thumb changeout on the city’s median 1,442 sq ft house tends to fit 4 tons where a real load calculation says 2.5 or 3. That is usually a humidity complaint rather than this one — but a mismatched indoor and outdoor unit produces exactly this. Why sizing matters here.

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.

Cost

What the fix typically costs

Researched repair ranges for this symptom
Job	Researched range	What drives it
Diagnostic visit	$75–$150	Ask for a static pressure reading as part of it.
Refrigerant leak repair	$200–$1,500+	Finding the leak is most of the cost.
Evaporator coil	$700–$2,500+	Rarely worth doing alone past twelve years.
Condenser coil	$1,000–$2,700+	Same caveat.
Duct repairs or replacement	$1,500–$5,000	Added to a changeout. Duke pays part of the test.

Read this before you use any number on this page

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.

Not getting anywhere?

Tell us the symptom, the build year of the house and roughly how old the equipment is. That usually narrows it to two candidates before anyone drives out.

Call for service Request a visit

Phone: (689) 308-3675 · Monday-Friday, 8:00 AM - 5:00 PM

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Sources

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.