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Repair · Lighting
Low voltage systems fail in three predictable ways: a joint underground that was never made properly, a run too long for the cable in it, or a transformer that was loaded to its rating on day one.
One fixture, or all
Where one fitting has stopped and the rest are fine, the joint feeding it is the first suspect. Connections made with tape or plain twist connectors and buried in soil corrode within a season or two, which is why gel-filled connectors exist and why we use nothing else outdoors. The same discipline applies to garage and shop wiring where a feed runs underground.
Where the far end of a run is visibly dimmer than the near end, nothing has failed at all: the cable is too small for the length. The answer is splitting the run or heavier cable, not a bigger transformer, and outdoor and landscape lighting sets out how that is calculated before anything is trenched.
Where fittings have gone one at a time over a season, the cause is usually the original installation method rather than bad luck, and repairing them individually is a slow way of paying for the whole system twice, and an electrical safety inspection of the whole run is the cheaper starting point.
How it runs
A tripped exterior device explains a good share of dead systems and costs nothing to rule out first.
Voltage at the near and far ends separates a fault from a run that was always too long for its cable.
Suspect connections are opened and inspected rather than guessed at, and remade in gel-filled connectors.
Checked when it is actually in use, with the timer or photocell set rather than left on manual.
Everything dead
When the whole system is out, the sequence is short: the outlet feeding the transformer, the transformer itself, then the control. An exterior outlet with ground fault protection that has tripped accounts for a good share of these, and it costs nothing to check first.
Where the supply outlet itself is the problem rather than the transformer, outlet and switch repair covers it, and an exterior device that keeps tripping usually means water is getting somewhere it should not, which is worth an electrical safety inspection rather than repeated resets.
Timers and photocells are the last item and the easiest to misread, because a system that works when tested manually but not on schedule is a control problem rather than a wiring one. Replacing one is a switch installation rather than a lighting repair.
Related work
Common questions
Dug up one joint, found tape under the soil, and replaced it properly.
Measured along the run and split it rather than selling us a bigger transformer.
It was the outdoor outlet. Checked that before anything else and it took minutes.
Came back after dark to set it properly instead of leaving it on manual.
From the blog
Next step
Tell us whether one fitting is out, the far end is dim, or the whole system is dead. Each points somewhere different.
Supply checked first · Joints opened, not guessed · Tested after dark