Dock Lights Not Working? A Saltwater Troubleshooting Checklist

Dock lights are one of those upgrades you don’t think about until they go dark. One night the canal glows and the water looks great — the next, you flip the switch and nothing. Before you assume the whole system is shot, take a breath. On a Southwest Florida saltwater dock, the vast majority of “dead” lighting traces back to a handful of predictable failure points, and several you can check yourself in ten minutes.

Here’s the troubleshooting checklist we walk through on service calls across Cape Coral, Fort Myers, and Naples — what’s safe to check yourself, and where the salt-and-water reality of our coast means it’s time to call a pro.

How are dock lights wired, and why does that matter?

Most dock lighting on our coast runs on a low-voltage system: 120-volt house power feeds a transformer that steps it down to 12 or 24 volts, which then runs out to the LED fixtures along the dock.

That chain has distinct links — the breaker, the GFCI outlet, the transformer, the timer or photocell, the wiring runs, and the fixtures. A failure anywhere breaks the lights downstream of it. The trick is starting at the power source and working outward, because most problems live closer to the panel than to the lights.

Did the GFCI or breaker trip?

Start here. A tripped GFCI outlet or breaker is the single most common reason dock lights go dark, and it’s a 30-second fix.

Any dock circuit on a Florida waterfront should be GFCI-protected — it cuts power the instant it detects current leaking to ground, which is exactly what you want around water. Splash, humidity, or a moisture-soaked fixture can trip it.

• Find the GFCI outlet feeding the dock (often on an exterior wall, in the garage, or in a weatherproof box near the seawall) and press Reset.
• Check the panel for a tripped breaker on the dock circuit — flip it fully off, then back on.
• If the lights come back and stay on, you’re done.

One caveat: if the GFCI trips again the moment the lights come on, stop resetting it. It’s catching a real fault — a waterlogged fixture or a flooded splice leaking to ground — and that needs to be repaired, not overridden.

Is the transformer getting power and sending it out?

If the breaker and GFCI are fine but the run is still dark, suspect the transformer. A failed or undersized low-voltage transformer will leave every fixture downstream dead.

The transformer converts house voltage down to low voltage. On the salt, these take a beating — corroded terminals, water intrusion, and tripped internal protection are all common. Check two things:

• Is it getting power in? Confirm the outlet it plugs into is live (a GFCI reset may be all it needed).
• Is it sending power out? The output terminals should read low voltage. No output with good input usually means the transformer has failed.

Undersizing is a quieter problem. If lights were added to an existing run and the transformer can’t supply enough wattage, you’ll see dim or flickering lights rather than total darkness — a sign it’s overloaded and needs to be upsized.

Is it the timer or photocell, not the lights?

Before you go hunting for corrosion, rule out the controller. A stuck timer or a failed photocell will make perfectly good lights look dead.

Many dock systems switch on automatically — a photocell senses dusk, or a timer runs a schedule. When those fail, the lights never get the signal:

• Put the timer or switch into manual / on. If the lights come up, your fixtures and wiring are fine and the controller is the culprit.
• A photocell fooled by a nearby light, blocked by debris, or simply worn out won’t trigger at dusk. Bypassing it to manual confirms it.
• After a power outage — common in hurricane season from June through November — a digital timer can lose its schedule and need a reset.

Are the connections corroded or the splices waterlogged?

This is the Southwest Florida failure point. Salt-corroded low-voltage connections and waterlogged underwater splices are the number-one reason dock lights die on our coast — more than any fixture defect.

Salt air, tidal splash, and humidity work into every connection on the dock. Low-voltage fittings that were never rated for marine use corrode from the inside, and a splice near the waterline can flood and short. The telltale signs:

• Green or white crust on terminals, connectors, or fixture leads
• A connection that’s wet, discolored, or crumbling when you touch it
• A single fixture or short stretch dark while the rest of the run works

The honest answer here: cleaning and re-sealing a corroded connection on a wet, salty dock is where owner troubleshooting ends and a pro begins. Done wrong, you trade a dead light for a safety hazard. Marine-rated connectors and sealed, waterproof splices are what make the repair last instead of failing again next season.

What if just one or two lights are out?

A single dark fixture changes the diagnosis. When most of the run works but one or two lights are out, the problem is local — a dead LED module or a corroded connection at that fixture — not the power source.

LED modules do eventually fail in a brutal UV-and-salt environment. And underwater lenses fog over with algae, calcium, and marine growth, so a light that looks “dead” may just be smothered. Quick checks:

• Wipe down a fogged or algae-covered lens; a clouded underwater fixture can look out long before it actually is.
• Swap a suspected dead LED module with a known-good one to confirm.
• Inspect that fixture’s connection for the corrosion described above.

Symptom	Most likely cause	Owner check or pro?
Whole run dark	GFCI, breaker, transformer, or timer	Owner check first
Dim or flickering	Undersized/failing transformer, voltage drop	Pro
One or two lights out	Dead LED module or local corrosion	Owner check, then pro
GFCI won’t stay reset	Fixture or splice leaking to ground	Pro — safety issue
Underwater light looks dim	Fogged or algae-covered lens	Owner check (clean it)

When should you stop and call a pro?

Stop the moment the fix involves live wiring, corrosion repair, or water. Resetting a breaker, flipping a timer, and cleaning a lens are safe. Opening up corroded saltwater splices, replacing a transformer, or chasing a fault that keeps tripping the GFCI is not a DIY job — and on a wet dock, the stakes are real.

One thing to take seriously: if you ever feel a tingle or shock in the water near your dock, get everyone out, kill the dock circuit, and call for help. That’s current leaking into the water, and it’s dangerous. We cover it in our dock electrical safety guide.

When dock lights fail on the salt, the right repair is the marine-grade one — sealed connections, properly sized transformers, and fixtures built for this environment — so you’re not back in the dark next season. Our own local crew handles dock lighting diagnosis and repair across all 18 Southwest Florida cities we serve, never subbed out. Explore everything we do on our dock lighting page or our dock repair page. We give free on-site estimates seven days a week across Cape Coral, Naples, and the rest of the coast — call (239) 397-3400.