Updated
Light Stuck On Dim
A light in your home is stuck at a low brightness and will not go to full brightness, or it glows faintly even when switched off.
Find an electrician
What's happening?
A light stuck on dim or glowing faintly can have several causes. If the light will not go above a low brightness when the switch is on, the dimmer switch may be faulty or set incorrectly. If the LED bulb glows faintly when the switch is off (known as 'ghosting'), a small leakage current is passing through the circuit — this is very common with LED bulbs on circuits that were originally wired for incandescent bulbs. The leakage is typically caused by two-way switch wiring, illuminated switches, or proximity to other cables inducing a small current.
What usually causes it?
- Dimmer switch set to minimum or the dimmer mechanism has failed
- LED ghosting — small leakage current causing a faint glow when switched off
- Illuminated or neon indicator switch leaking current through the LED
- Incompatible dimmer switch not delivering full power to the LED bulb
- Partially failed LED driver inside the bulb limiting brightness
Is it dangerous?
This is generally low risk. LED ghosting (faint glow when off) is an annoyance rather than a danger — the current involved is tiny. However, if the light is dim when it should be at full brightness and the wiring is warm, there could be a loose connection limiting the current flow, which is a fire risk. Check the switch faceplate temperature.
Can I fix it myself?
If the light is on a dimmer, check the dimmer is turned up fully and the minimum level trim (if fitted) is set correctly. If the LED glows faintly when the switch is off, try a different brand of LED bulb — some are more susceptible to ghosting than others. An LED bypass capacitor (a small device fitted at the light fitting) can absorb the leakage current and stop ghosting. If the light is genuinely dim at full power, try a new bulb first.
When should you call an electrician?
Call an electrician if a new bulb does not resolve low brightness (suggesting a wiring fault), if you want a bypass capacitor fitted at the light fitting, if the dimmer needs replacing, or if the switch is warm to the touch (suggesting a loose connection).
What will the electrician actually do?
- Test the circuit to determine why the light is not receiving full power
- Check for loose connections that may be limiting current flow
- Fit a bypass capacitor at the light fitting to resolve LED ghosting
- Replace an incompatible dimmer with a suitable LED trailing-edge model
- Test the wiring for induced voltages from adjacent cables
What will it cost to fix?
£50–£130
Fitting a bypass capacitor is a quick, low-cost fix. Dimmer replacement or fault-finding in the circuit will cost more.
Find an electricianFrequently asked questions
We’re happy to answer all your questions.
Why does my LED light glow faintly when switched off?
This is called LED ghosting. A small leakage current is passing through the circuit even when the switch is off. Common causes include illuminated switches, two-way wiring, and capacitive coupling from adjacent cables. It is harmless but annoying.
What is a bypass capacitor?
A bypass capacitor is a small device fitted at the light fitting that absorbs the tiny leakage current causing LED ghosting. It provides an alternative path for the current so it does not flow through the LED. They cost around £5 and are very effective.
Why is my light dim even at full brightness?
If the light is on a dimmer, the dimmer may be incompatible with your LED bulb or faulty. If it is on a standard switch, a loose connection may be limiting the current. Try a new bulb first — the LED driver inside the bulb may have partially failed.
Sources & References
Need an electrician?
Compare local electricians on Tradehand — coverage areas, accreditations and phone numbers, no middleman.
Find an electrician