Outdoor Light Not Working: Troubleshooting Guide

Your outdoor light has stopped working — the security light does not come on, the garden lights are dark, or the porch light is dead. Outdoor lights face challenges that indoor lights do not: rain, frost, UV exposure, temperature swings, and insects — all of which take a toll on electrical fittings over time.

The cause could be as simple as a tripped breaker or a failed bulb, or as complex as a damaged underground cable or a corroded junction box buried in a garden wall. Outdoor electrical faults also carry a higher safety risk because of the combination of electricity and water.

This guide covers every common cause of outdoor light failure, explains what you can check yourself safely, and tells you when to call an electrician. If you are an electrician, the later sections cover outdoor circuit fault finding and the specific challenges of weatherproof installations.

Before investigating further, rule out the simple causes:

Moisture ingress is the number one cause of outdoor light failure. Every outdoor light fitting has an IP (Ingress Protection) rating that indicates its resistance to water and dust. When the seals, gaskets, or enclosure degrade, the IP protection fails and water gets in.

When water reaches the internal terminals or driver, it causes short circuits (tripping the MCB), earth faults (tripping the RCD), or corrosion of components (gradual failure). The fix is usually to replace the fitting with a new one of adequate IP rating, ensuring all cable entries are properly sealed.

Many outdoor lights incorporate sensors for automatic operation. These sensors are the most exposed electronic components and are common failure points:

SWA (Steel Wire Armoured) cable is the standard cable type for outdoor underground circuits in the UK. It has a tough steel wire armour layer that provides mechanical protection and acts as the circuit protective conductor (earth). Despite its toughness, SWA cable can be damaged:

Outdoor lights are one of the most common causes of RCD tripping in UK homes. The combination of electrical equipment and weather exposure means earth faults are frequent.

Under Regulation 411.3.3 of BS 7671, additional protection by an RCD with a rated residual operating current not exceeding 30mA is required for socket outlets rated up to 32A and for mobile equipment rated up to 32A used outdoors. Outdoor lighting circuits should also have RCD protection as good practice, and this will be required where the circuit supplies socket outlets or where specified by the designer.

If your outdoor lights trip the RCD, the fault needs to be found and repaired — not simply reset repeatedly. Each RCD trip indicates current flowing through an unintended path, which could be dangerous.

Most modern outdoor lights use LED technology, and the LED driver (also called the transformer or power supply) is the component most likely to fail. LEDs themselves are very long-lived, but the electronic driver that converts mains voltage to the low voltage the LEDs need is more vulnerable.

In some fittings, the driver is replaceable separately — look for a model number on the driver and source a replacement. In many integrated LED fittings, the driver is built in and the entire fitting must be replaced when the driver fails.

Outdoor lights are often controlled by timers or dusk-to-dawn modules that automate their operation. When these controllers fail, the light may not operate at all, stay on permanently, or operate at the wrong times:

Corrosion is the silent killer of outdoor electrical installations. It works slowly — sometimes over years — but eventually causes connection failure. Junction boxes, terminal blocks, and cable glands are the most vulnerable points.

Outdoor electrical work carries higher risk than indoor work because of weather exposure. Here is when to call a professional:

An electrician will test insulation resistance on the outdoor circuit, check all connections and IP-rated enclosures, verify RCD protection is present and operational, and ensure cables are properly routed and protected. They should issue a Minor Works Certificate for any repair or replacement work.

Outdoor circuit faults require a methodical approach, particularly because access to buried cables and remote fittings can be challenging:

Document outdoor lighting work with professional

Elec-Mate lets you complete Minor Works Certificates and EICRs on your phone with full test result recording, photo attachments, and instant PDF export.

Try it free for 7 days