Is it corrosion? The Miami diagnostic
Salt air off Biscayne Bay and the Atlantic attacks aluminum fins, copper tubing and every electrical connection in an outdoor unit. Within a few miles of the water a condenser ages twice as fast. Match what you see to the row:
| What you see | What it usually is | What it takes |
|---|---|---|
| White, chalky fins that crumble when touched | Galvanic corrosion on the condenser coil. Common in Miami Beach, Key Biscayne, Aventura, Sunny Isles and anywhere east of US-1. | Coil replacement if the tubes are still sound; condenser replacement if a leak has started. Ask for a coated coil on the new unit. |
| Green crust at a brazed joint, oily residue | Refrigerant leak from formicary or galvanic pitting. | Leak search, braze or coil, evacuate and recharge. |
| Unit hums, fan does not spin, contactor looks rusty | Capacitor most often; corroded contactor or wiring terminals second. | Capacitor $150–$400; contactor and terminal clean-up similar. |
| Breaker trips, burned smell at the disconnect | Corroded disconnect or wire lugs arcing. | Electrical repair. Stop running it. |
| Cabinet rusted through at the base, fan shroud loose | Sheet-metal corrosion. The unit still runs but is at end of life. | Budget for replacement; FPL pays $200 toward it (below). |
| Nothing corroded, water on the floor | Not corrosion. Condensate drain — the other Miami call. | Clear and treat the line, check the float switch. |
Twelve months of cooling
Miami logs about 4,190 cooling degree days a year and roughly 140 heating degree days (NOAA normals). It is the only one of the five metros in IECC climate zone 1A. A system here never gets the six-month rest that resets algae in the drain line or lets a marginal capacitor cool off — it runs 4,000-plus hours a year, which is why ten-year-old Miami equipment is old.
Calls peak from late May through September, with a second surge after any hurricane or tropical storm: surges and brownouts when power comes back take out control boards and capacitors, and units that took water in a flooded yard need to be inspected before they are switched on. Dew points sit in the mid-70s all summer; dehumidification is half the job, and an oversized unit that short-cycles leaves the house clammy at 76°F.
Where in Miami-Dade and Broward
Coverage runs the length of Miami-Dade — Homestead and the Redland in the south, Kendall, Pinecrest and Coral Gables, the City of Miami, Doral and Hialeah west and north, Miami Beach and Aventura on the coast — and across the county line into Broward: Hollywood, Pembroke Pines and Fort Lauderdale.
What differs by area is the housing and the air. Concrete-block single-story homes in Hialeah, Westchester and Kendall from the 1960s–80s typically have the air handler in a garage or utility closet and a condenser on a side pad; the drain line often runs to a yard that floods. High-rise condos in Brickell, Miami Beach, Aventura and along the Fort Lauderdale beach use small split systems or packaged terminal units in salt air with building-management rules about who may work on them — tell us if it is a condo. Post-2000 homes in Doral, Homestead and Pembroke Pines have attic air handlers and the ceiling-stain drain problem.
Miami-Dade permits: what a repair needs and what it does not
Miami-Dade County's Department of Regulatory and Economic Resources issues mechanical permits for air conditioning work, and the county publishes a specific exemption list. For a repair call the practical rules are:
- Exempt: repair or replacement of a coil, compressor or refrigerant piping inside the equipment, when done by a licensed air conditioning or mechanical contractor. Replacing a window unit. Most repair calls fall here.
- Permit required: replacing the system, including an exact change-out. The county's mechanical fee sheet prices a change-out per ton, and the contractor pulls it through the county's e-permitting system. Homes inside the cities of Miami, Hialeah, Coral Gables, Miami Beach and the Broward cities go through those cities' building departments instead.
- Inspection: a permitted change-out gets a mechanical inspection; the permit is open for 180 days.
Current forms and the exemption list are on the Miami-Dade County Building department site. Florida contractors are licensed by the state's Department of Business and Professional Regulation; ask for the CAC (certified) or RA (registered) license number.
FPL's rebate, and why it matters to a repair call
Florida Power and Light serves nearly all of Miami-Dade and Broward. FPL pays an instant $200 rebate, credited on the invoice, when a new A/C system — indoor and outdoor units together — is installed by one of its Participating Independent Contractors. It does not pay for repairs, and FPL is explicit that the contractor list is a program list, not an endorsement.
It matters here because so many Miami repair calls end at a corroded, eleven-year-old condenser where the honest answer is replacement. Ask whether the contractor is an FPL PIC before the quote is written. Program page: FPL residential programs. The federal 25C credit ended for equipment placed in service after 2025.
The other Miami failures
- Condensate drain. Algae in the line year-round. Float switch trips, system goes dark. Clear it, treat it, and put a float switch on any system that lacks one — a flooded pan in a Kendall garage is cheap, a flooded pan in a Doral attic is drywall.
- Frozen coil in a wet house. Latent load plus a neglected filter. Off, FAN only, thaw, replace the filter, then call if it ices again.
- Post-storm electrical. Boards, capacitors and contactors after a surge; salt-water intrusion in a flooded condenser. Do not run a unit that stood in water until it is inspected.
- Short cycling on an oversized unit. A 4-ton unit on a 2.5-ton house cools fast and leaves the humidity. It is not a fault the tech can fix; it is a sizing conversation.
Miami repair costs
Labor in Miami sits toward the top of the five metros, and coastal corrosion makes coil and condenser work more common than inland. Typical ranges:
- Diagnostic
- $90–$160
- Drain clear, treat, float switch
- $110–$260
- Capacitor
- $160–$400
- Contactor + terminal clean-up
- $160–$360
- Leak repair and recharge
- $450–$1,600
- Condenser coil, coated
- $1,300–$2,600
- Compressor
- $1,600–$3,100
Two of the rows above are replacement conversations more often than not. What a new system costs in Miami and how the FPL rebate and the county permit fit in. Symptom-by-symptom causes for any metro: the AC repair page. Tropical outlook and heat advisories: National Weather Service Miami.