The most likely fix on an AquaCal that's short cycling or heating weakly:clean the evaporator coil and check water flow first — those are the two homeowner-checkable causes. Beyond that, you're into refrigerant or electrical territory, which is licensed-tech work. In our experience, Florida heat pumps fail in three ways: salt-corroded coils, refrigerant leaks at brazed joints, and contactor/capacitor electrical failures. Defrost behavior in cool weather is normal — don't mistake it for a fault.
Most common symptoms
- Compressor cycles on/off rapidly without warming the pool.
- Pool barely climbs 1–2°F over an 8-hour heat call.
- Ice on the evaporator coil that doesn't clear.
- Unit displays HP (high pressure) or LP (low pressure) faults.
- Fan runs but compressor doesn't kick on.
- Loud bang or whoosh followed by cool air discharge.
Diagnostic walkthrough
- Pin the symptom. Short cycling? No heat? Ice? Fault display? They diagnose differently.
- Water flow. Heat pump needs roughly 30 GPM (model-dependent). Low-flow protection trips early. Filter cleanings, valve positions, plumbing checks.
- Air flow. Top fan spinning at speed. Coil clean. Two feet of clearance on all sides. Florida pads with palm-frond debris choke heat pumps in 30 days.
- Defrost vs. fault. A short defrost cycle (5–15 minutes) on a 50°F morning is normal. See our heat pump defrost guide for full context.
- Visual leak inspection. Oily film at copper joints, missing brazing, tarnished compressor leads. Refrigerant doesn't evaporate — if it's gone, it leaked.
- Electrical. Contactor pulling in cleanly when the controller calls? Run capacitor not bulged? Compressor terminals not corroded green? Florida coastal pads kill these in 5–7 years.
Step-by-step fix
Coil cleaning is homeowner-safe with the power killed and locked out: garden hose from inside the cabinet outward, soft brush on heavy lint, fan blade clearance check. Capacitor replacement is licensed-tech work — even with power off, the capacitor stores hazardous voltage and rotor windings can re-induce a charge after bleed. Anything refrigerant-side — recovery, leak repair, brazing, recharge — requires a tech with EPA Section 608 certification under federal law (Clean Air Act §608, 40 CFR Part 82, Subpart F). Sealed-system work is not DIY.
South Florida-specific failure modes
- Salt-air pinhole leaks at the brazed joints. Coastal heat pumps lose refrigerant through pinholes in copper that rusted from salt deposits. Annual fresh-water rinse on the coil and copper extends life noticeably.
- Lightning damage to the controller. In our field experience, Florida summer storm season is hard on heat pump control boards.
- Palm-frond and oak-leaf coil clogging. The coil is a giant lint screen. Quarterly cleaning during pollen and leaf seasons.
- Capacitor failure under heat. 95°F equipment pads kill run capacitors in 4–6 years vs. 8–10 in cooler climates. Cheap part, common failure.
When it's time to replace
A 10+ year AquaCal with a refrigerant leak, a corroded cabinet, and a soft compressor often isn't worth the repair. Newer units typically rate higher COP at AHRI conditions than legacy models — verify the rated COP for the candidate model against the AquaCal data sheet. As a rough rule, if the repair quote crosses 50% of new-unit price, replace. See our pool heater comparison for sizing the next one.
When to call a pro
Refrigerant work is licensed by federal law (EPA Section 608). Diagnosing a leak, recovering refrigerant, brazing a joint, recharging — none of those are DIY. Capacitor and contactor work also requires power-off lockout and licensed-pro handling. In Florida, residential pool repair work is regulated by the DBPR (RP / CPC license categories). Get a pool equipment repair visit scheduled and we'll put a certified tech on it with a flat-rate quote.
FAQ
Why does it short cycle? Low refrigerant, failed pressure switch, or failed reversing valve.
Is ice on the coil normal?A thin frost on a cool morning, yes. Solid ice that won't clear, no.
How do I know if I need refrigerant? Weak heating, short cycling, oily residue at joints. Confirmed only with gauges.
What is the whoosh sound? The reversing valve flipping the unit into or out of defrost.
How long should it last?8–12 years inland, 6–8 on the coast.
Want a pro to handle this?
Our CPO-certified techs run this exact playbook on every weekly service visit.