Low Voltage Landscape Lighting Not Working? A Diagnostic Guide

Low voltage landscape lighting is designed to be DIY-friendly — but when lights start flickering, going dim, or dying one by one, the cause isn’t always obvious. Here’s a systematic approach to diagnosing the most common low-voltage landscape lighting problems.

Start with the transformer

The transformer converts 120V AC to 12V for the fixtures. If a large number of lights are out or dim simultaneously, start here. Check that the transformer is plugged in, the outlet has power, and any built-in GFCI on the outlet hasn’t tripped. Most landscape transformers have an overload protection fuse — check and replace it if blown. Test the transformer’s output voltage with a multimeter at the terminals: you should see 12V ± 10%. Readings below 10V indicate a failing transformer or significant voltage drop in the cable run.

Check for voltage drop along the run

Voltage drop is the most common cause of dim or dead landscape lights, especially when fixtures are added over time to an existing run. Test voltage at the transformer terminals, then at the last fixture on each run. A drop of more than 2V means the wire run is too long, the wire gauge is too small, or too many fixtures are connected. The fix: split long runs into two shorter ones from the transformer, upgrade the cable to 12 AWG, or reduce fixtures per run. Most residential landscape cable is 16 AWG, which handles about 100–150 watts over a 15-metre run before dropping below threshold.

Check individual fixture connections

Piercing connectors — the snap-on quick-connectors used in most landscape systems — corrode over time, especially in Ontario’s freeze-thaw cycles. Inspect each connector: look for green corrosion on the contacts and check that the wire is fully seated. For corroded connectors, cut back the wire a few centimetres past the corroded section and install new connectors. If you’ve had the system for more than 5 years, replacing all piercing connectors with waterproof gel-filled wire-nut splices is a worthwhile upgrade that eliminates most connection failures.

When individual lights are out

If isolated fixtures are dead while neighbours on the same run work fine, the problem is local: a burned-out bulb (replace with LED for longer life), a corroded socket, or a failed connector at that fixture. Remove the fixture, clean the socket contacts with electrical contact cleaner, and test with a known-good bulb. If the socket is corroded through, the fixture housing usually needs replacing.

Expert tip

The best landscape lighting upgrade we recommend is switching from halogen MR16 or G4 bulbs to LED replacements. The energy saving is 80–85% per fixture, the bulbs last 25,000+ hours instead of 2,000, and LED drivers are less sensitive to voltage drop than halogens — meaning the system works better even on runs where voltage was marginal before. A 10-fixture halogen system drawing 50W per fixture (500W total) becomes roughly 75W total on the same transformer with LEDs — dramatically reducing load and transformer heat.

Contact us

Landscape lighting not working the way it should? Call us at 416-838-9006 or visit our contact page — we service and upgrade landscape lighting systems across the GTA.

Amir Azimipour

Electrician Since 2008 Journeyman Electrician Designated Master Electrician at EZSMART Corp