Why do outdoor lights keep tripping?

Outdoor lighting trips are usually a water-and-wiring problem, not a bad breaker. The pattern matters: if it trips during rain, after snowmelt, or the morning after heavy condensation, start with wet fixtures, buried splices, and GFCI protection before assuming the panel is the issue.

If you have line-voltage exterior lights, the fault may be in a weatherproof box, photocell, switch leg, underground conduit, or outdoor receptacle feeding the lights. If you have low-voltage landscape lighting, the issue is more often a damaged cable, overloaded transformer, corroded connector, or fixture full of water.

The most common cause is water getting where it should not be

Water inside an outdoor electrical connection can trip a GFCI, breaker, or transformer even when the lights look normal from the outside. Rain and snowmelt find small openings: a missing gasket, a fixture aimed upward, a cracked lens, a loose conduit hub, or a splice sitting in mulch.

We often see the timing tell the story. Lights that run fine in July but trip after freeze-thaw weather in March are usually reacting to moisture in a connection. Snow melts into a box during the day, freezes at night, then re-melts and creates a leakage path between hot, neutral, and ground.

Check these outdoor-specific failure points:

• Wall lanterns with failed foam gaskets behind the canopy
• Soffit or porch fixtures where the box is not sealed to the exterior surface
• Landscape bullet lights tilted upward and holding water behind the lens
• Underground junction boxes that sit below grade or fill with soil
• Photocells and timers with cracked plastic housings
• Low-voltage wire nuts buried directly in mulch instead of using waterproof connectors
• Cable nicked by a shovel, lawn aerator, edging tool, or snow stake

A GFCI is designed to trip when current leaks away from the intended path. That is why an outdoor lighting problem may trip a receptacle in the garage, basement, or exterior wall instead of the panel breaker. If your reset button pops immediately, read our guide to GFCI devices that keep tripping before repeatedly forcing it back on.

Do not keep resetting the circuit after rain if it trips again. Repeated resets can heat a wet connection, carbon-track a device, or damage a transformer. The safer move is to leave it off, note which lights were on, and let the equipment dry until it can be tested properly.

Low-voltage landscape systems trip for different reasons than house-voltage lights

Low-voltage landscape lighting usually trips because the transformer is overloaded, the secondary cable is damaged, or the splices are corroded. These systems are safer than 120V lighting at the fixture, but they still fail when the installation is not weather-rated.

A typical low-voltage setup has a 120V feed to a transformer, then 12V or similar wiring out to path lights, spotlights, and garden fixtures. The transformer may have an internal reset, fuse, thermal cutout, or breaker. When it trips, it may look like the entire outdoor lighting zone has died.

Common low-voltage causes include:

Transformer loading matters. LED fixtures draw less than old halogen lamps, but the transformer still has a maximum output. If a homeowner adds fixtures over time, the system can creep past its safe operating range. A transformer may run for a while, heat up, and then shut down every evening.

The fix is not to install a larger transformer blindly. The cable size, run length, connection method, and fixture load all have to match. A properly built outdoor lighting installation uses weather-rated fixtures, direct-burial cable where required, waterproof low-voltage connectors, strain relief, drip loops, and accessible splices instead of twist-on connectors buried in soil.

A tripping outdoor lighting circuit should be separated into zones before parts are replaced

The fastest diagnosis is to isolate the fault instead of guessing at fixtures. Outdoor lighting often has several parts in series: indoor switch, exterior box, timer, photocell, GFCI, transformer, underground cable, and multiple fixtures. Any one of them can trip the circuit.

A useful sequence is:

• Turn the outdoor lighting circuit off and leave wet equipment off.
• Note whether the trip happens instantly, after several minutes, only at dusk, or only after weather.
• Unplug or disconnect the low-voltage transformer if it is cord-and-plug connected to a GFCI-protected receptacle.
• Reset the GFCI or breaker with the transformer disconnected.
• If it now holds, the fault is likely downstream of the transformer or in the transformer itself.
• If it still trips, the problem is likely the receptacle, feed, switch, box, or line-voltage wiring.
• Reconnect one lighting branch at a time where the system is designed for service access.

Do not open energized outdoor boxes or pull fixtures apart in wet conditions. A line-voltage circuit can be dangerous even when the lamps are off, because the switch may interrupt only one conductor and the box may still contain live feeds.

For buried low-voltage lighting, a clamp meter, insulation testing where appropriate, and branch-by-branch disconnection can find the bad run without digging up the whole yard. For 120V outdoor lighting, testing should confirm whether the breaker is tripping from overcurrent, the GFCI is tripping from leakage, or an arc-fault device is reacting to damaged wiring.

If the panel breaker trips, the issue may be a short circuit or overload rather than a ground fault. Our guide to circuit breakers that keep tripping explains that difference. If the lights are plugged into or fed through an exterior receptacle, also check whether an outdoor outlet has stopped working because of an upstream GFCI.

Weather-rated parts and proper connections prevent the repeat trip

The long-term fix is to rebuild the weak outdoor points with equipment rated for the location, not to keep drying and resetting the same system. Exterior electrical work fails when indoor parts are used outside or when connections are left where water naturally collects.

For line-voltage outdoor lighting, the repair may include:

• Weather-rated fixture boxes and covers
• Proper gaskets between the fixture canopy and the wall or soffit
• Outdoor-rated cable or conductors in approved raceway where required
• Correct bonding and grounding of metal boxes and fixtures
• In-use covers for receptacles feeding plug-in transformers
• GFCI protection where required for outdoor receptacles
• Photocells, timers, and smart controls rated for exterior use or installed indoors

For low-voltage landscape lighting, the repair may include:

• Direct-burial landscape cable sized for the run length and load
• Waterproof, gel-filled, or listed low-voltage splice connectors
• Splices kept accessible and out of standing water where practical
• Fixtures mounted so lenses and wire entries do not trap water
• Transformer sizing based on actual connected load, not guesswork
• Separate runs for long paths, heavy fixture groups, or front-and-back yard zones

If a lighting run was installed years ago with ordinary wire nuts wrapped in tape, expect corrosion. Tape is not a waterproof enclosure. Once copper turns green and brittle, cutting back to clean conductor and remaking the connection with the right connector is usually more reliable than trying to clean the old splice.

Some outdoor lighting work needs an ESA notification, especially new 120V circuits, new exterior wiring, or changes to fixed wiring. City Power Electrical Services is an ECRA/ESA licensed electrical contractor, #7015314, and where required we file the ESA notification, complete the repair, and leave the area cleaned up.

Call an electrician when the trip repeats after weather or affects fixed wiring

You should call a licensed electrician when outdoor lights trip more than once, trip after rain or snowmelt, trip a GFCI that will not reset, or involve buried 120V wiring. These are not good trial-and-error jobs because water faults can disappear when the sun comes out and return during the next storm.

Call sooner if you notice:

• A burnt smell at an exterior box, timer, transformer, or switch
• A breaker that trips instantly when reset
• A GFCI that trips with nothing plugged in
• Lights that flicker before the trip
• A transformer that is hot, buzzing, or discoloured
• A fixture full of water
• Exposed cable, chewed insulation, or damaged conduit
• Tripping that affects a pool, spa, garage, shed, or exterior receptacle circuit

Troubleshooting is also worthwhile before replacing a landscape system. If only one branch cable is damaged, the rest of the fixtures and transformer may be reusable. If the transformer is undersized or water-damaged, replacing only the tripping fixture will not solve the shutdown.

For homeowners comparing symptoms, landscape lights that are not working is the better page when the system is dead but not tripping. This page is for trips: the protective device is doing something because it sees leakage, heat, overload, or a fault.

If you are in Toronto or the GTA, we can test the GFCI, transformer, fixture wiring, photocell, buried cable branches, and panel connection, then quote the repair in writing. Low-voltage landscape lighting packages commonly start around $1,500–$3,000 for a front yard, while fault repairs are quoted after testing because the buried cable and access conditions decide the scope.