What is this?
Lights that pulse rhythmically (rather than flickering randomly) often indicate a specific electrical issue such as a failing component, a loose connection that is arcing at regular intervals, or electrical interference. The regular pattern distinguishes this from random flickering and can help pinpoint the cause.
Common causes
- Failing LED driver producing unstable output
- Incompatible dimmer switch cycling the power to the bulb
- Loose connection that is arcing and cooling in a regular pattern
- Faulty smart bulb or smart switch with a connectivity issue
- Electrical interference from a nearby device on the same circuit
- Transformer failing in a low-voltage lighting system
Is it dangerous?
Pulsing lights are more concerning than a simple flicker because the regularity suggests an active and ongoing fault rather than a one-off event. A connection that is arcing rhythmically is generating heat each time and is a fire risk. If the pulsing is rapid and continuous, turn the light off and get it checked.
Can I fix it myself?
Try replacing the bulb first — a failing LED driver is a common cause. If you have a dimmer, check whether the pulsing stops with the dimmer set to full brightness. For smart bulbs, check the app for firmware updates or try re-pairing the bulb. If the pulsing affects multiple lights, the issue is likely in the circuit or consumer unit and you should not attempt a fix yourself.
When to call an electrician
Call an electrician if replacing the bulb does not fix the pulsing, if multiple lights are affected, if the pulsing is accompanied by buzzing or a burning smell, or if the lights pulse even when the switch is turned off (which can indicate a wiring fault or a switch that is not fully breaking the circuit).
What will an electrician do?
Diagnose whether the pulsing is caused by the bulb, fitting, switch, or circuit
Test the dimmer switch output with an oscilloscope or power analyser
Check for loose connections that may be arcing periodically
Replace failing transformers or LED drivers
Isolate and resolve any sources of electrical interference
Replace the dimmer with an LED-compatible model if needed
Typical cost
£70 – £200
If the cause is a simple bulb or dimmer replacement, costs are at the lower end. Fault-finding on the circuit costs more.
