Old rewireable fuse blowing repeatedly
An older home with ceramic rewireable fuses keeps blowing a fuse on one circuit — the fuse is doing its job; something is overloading or faulting that circuit.
Safety first
Never fit thicker/heavier fuse wire to stop a fuse blowing — that removes the protection and is a serious fire risk. Isolate before working at the fuse board.
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.
Apprentice mode
Full walk-through — the why, what readings mean, mistakes & safety.
Likely causes
Ranked from most to least likely.
- 1
Circuit overload
Most likelyToo much load on an older circuit blows the fuse — common as appliance loads have grown.
- 2
Faulty appliance shorting/overdrawing
#2An appliance fault overloads or shorts the circuit.
- 3
Short circuit in the wiring
#3A short blows the fuse instantly.
- 4
Wrong/over-thick fuse wire previously fitted
Least likelyHeavier wire fitted before may have masked a real fault now surfacing.
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.
On the tools? Job Mode shows one test at a time with thumb-sized buttons — your place and readings carry straight over.
Enter Job ModeConfirm the correct fuse-wire rating is fitted, then note whether it blows instantly or after load.
Correct fuse wire; a pattern (instant vs after load).
Instant → short; after load → overload/appliance.
Wrong/over-thick wire fitted — correct it first.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
Fuse keeps blowing
→ step 2 - 2decision
Is the correct fuse-wire rating fitted?
Yes→ step 3No→ step 4 - 3decision
Does it blow after load (vs instantly)?
Yes→ step 5No→ step 6 - 4result
Wrong/over-thick wire — fit the correct rating first.
- 5decision
Does removing high loads stop it blowing?
Yes→ step 7No→ step 8 - 6result
Instant — test for a short/earth fault and repair.
- 7result
Overload or faulty appliance — rebalance / repair.
- 8result
Blows with all off — wiring fault; have it repaired.
Common mistakes apprentices make
- Fitting heavier fuse wire to stop it blowing (dangerous).
- Not checking the correct fuse rating is fitted.
- Resetting into a short repeatedly.
- Ignoring that old circuits may be genuinely overloaded by modern appliances.
When to stop & escalate
This is licensed electrical work; never defeat the fuse. Repeated blowing on an old board often warrants a switchboard upgrade assessment by a licensed electrician.
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.
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Related faults
A circuit breaker keeps tripping (domestic)
One circuit breaker keeps tripping — instantly on reset or after a load runs — and you need to tell an overload from a short or a faulty appliance.
MCB (circuit breaker) keeps tripping
A circuit breaker trips repeatedly — instantly on reset, or after a load runs for a while — and you need to tell a short from an overload from a faulty breaker.
Switchboard buzzing, warm, or smells hot
The switchboard hums/buzzes, feels warm, or has a hot/burning smell — a sign of a loose connection or an overloaded device, and a genuine fire-risk warning.
Learn the theory
How the gear and circuits behind this fault actually work.