Downlights cutting out then coming back
Downlights switch off after a while then come back once cooled — classic thermal cut-out behaviour, usually from heat build-up around the fitting or driver.
Safety first
Downlights and their drivers get hot; insulation contact is a known fire risk. Isolate before working in the ceiling and never cover a fitting that isn't rated for it.
Isolate, lock out / tag out, and prove dead before working unless a live test is specifically required, authorised, and carried out under proper supervision. Always follow local regulations, your site procedures, and the equipment manufacturer's documentation.
Full detail — causes, the why, and common mistakes.
Likely causes
Ranked from most to least likely.
- 1
Thermal cut-out from insulation/heat build-up
Most likelyInsulation packed against a non-IC-rated fitting, or poor airflow, makes it overheat and cut out until it cools.
- 2
Failing driver overheating
#2A driver near end of life runs hot and shuts down intermittently.
- 3
Too many fittings on one driver / overloaded
#3An overloaded driver overheats and drops out.
- 4
Poor ventilation in the ceiling space
Least likelyA hot roof space with no airflow pushes fittings over their limit.
Reports are saved on this device to reflect what you actually find.
Testing sequence
Work through one test at a time. Expected reading and what each result means.
Confirm the timing pattern: does it cut out after running a while and recover once cool?
Cut-out after heat build-up, recovery after cooling.
Thermal pattern confirmed — check insulation contact and ventilation.
If it's random/instant, suspect a driver or connection fault instead.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
Downlights cutting out
→ step 2 - 2decision
Does it cut out after heat build-up and recover when cool?
Yes→ step 3No→ step 4 - 3decision
Is insulation clear of the fitting / is it IC-rated?
Yes→ step 5No→ step 6 - 4result
Random/instant — suspect driver or connection fault.
- 5decision
Is the driver within rating and the space ventilated?
Yes→ step 7No→ step 8 - 6result
Insulation contact on a non-IC fitting — correct clearance.
- 7result
Suspect a failing driver — replace.
- 8result
Overloaded driver or hot space — correct it.
Common mistakes apprentices make
- Packing insulation against a non-IC-rated downlight (fire risk and cut-outs).
- Replacing globes when it's the driver overheating.
- Overloading one driver with too many fittings.
- Ignoring a baking-hot roof space with no airflow.
When to stop & escalate
Insulation clearance and IC-rating are safety matters — a licensed electrician should correct non-compliant or overheating installations. Repeated thermal cut-outs point to a fitting/clearance design issue, not just a globe.
If you're past your competence, authorisation, or the safe limits of the job — stop and hand it on. There's no fault worth getting hurt over.
Related faults
Lights flickering
One or more lights flicker — constantly, intermittently, or when other appliances run. Common with LEDs and dimmers, but can also signal a loose connection.
A single light not working
One light fitting is dead while the rest of the lights on the circuit work fine — points at the lamp, the fitting, or the switch for that point rather than the whole circuit.
Bathroom/laundry exhaust fan not working
An exhaust fan won't run, runs weakly, or keeps running — common causes are the switch/timer, a seized/dusty motor, or supply.