Bathroom Electrical Faults · Kettering & Northamptonshire · NAPIT-Registered
Extractor Fan or Bathroom Light Not Working?
Bathroom electrical faults are more nuanced than they appear. Zone compliance, isolator requirements, switched and permanent lives for timer fans — getting it right matters both for function and for safety in a wet location.
Zone
Compliant Work
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Registered
Part P
Certified
Attendance
Confirmed First
Understanding the Fault
Why Bathroom Electrical Faults Need a Careful Approach
Bathrooms and wet rooms are special locations under BS 7671, the UK wiring regulations. That classification exists because water and electricity are a genuinely dangerous combination — and the consequences of an electrical fault in a wet environment are more serious than elsewhere in the property.
The classification system divides bathrooms into zones based on proximity to the water source. Each zone has minimum IP (Ingress Protection) rating requirements for electrical accessories and fittings. Work in these locations must be carried out by a competent person, tested and certified.
When a bathroom fan or light stops working, the fault could be at the accessory itself, at the isolator, in the wiring between the two, or at the circuit protection in the consumer unit. We diagnose systematically — starting with what's most likely given the symptom — rather than opening every access point until something looks wrong.
Bathroom Zones — What They Mean
Zone 0
Inside the bath or shower basin
Minimum IP67. Only SELV 12V max permitted. No standard accessories.
Zone 1
Directly above bath/shower to 2.25m
Minimum IP44. Only 240V if specifically designed for this zone. Commonly where shower downlights are fitted.
Zone 2
0.6m beyond zone 1 boundary
Minimum IP44. Standard accessories not permitted unless IP-rated. Extractor fans are commonly here or in the ceiling above zone 1.
Fan Wiring — The Key Issue
Switched Live vs Permanent Live: Why Timer Fans Fail
The single most common reason a newly-installed timer fan doesn't work correctly is a missing or disconnected permanent live. Understanding why matters:
What each conductor does
Permanent Live (L)
Always live regardless of switch position. Provides power to the fan's electronics and timer circuit so the fan can continue to run after the bathroom light is switched off.
Switched Live (SL)
Only live when the bathroom light switch is on. Signals the fan to start. When this goes off, the timer takes over — powered by the permanent live — to run the fan on for the set overrun period.
Neutral
Return conductor. Required for both the switched and unswitched functions. Without it, the fan has no return path for current.
Fan Isolator
Not every fan installation has the same isolation requirement. The correct arrangement depends on the fan, circuit design, manufacturer’s instructions and the provision required for safe maintenance. Where a fan uses permanent live, switched live and neutral conductors, a suitable three-pole isolator is commonly installed so those conductors can be isolated together for maintenance. The existing installation should be assessed rather than assuming one arrangement applies universally.
A fan that only has a switched live (typical of older non-timer installations) will spin when the light is on and stop immediately when the light goes off — even if it's a timer fan. The timer cannot operate without the permanent live. This is the most frequent cause of "timer not working" calls.
What We Check
Common Causes We Look For
Failed fan isolatorThe fan isolator is the point most people ignore — and the most common single failure point. If the isolator's contacts have failed internally, the fan receives no supply regardless of the switch or wiring condition. We check for voltage at both the supply and load terminals of the isolator to confirm whether it's passing or blocking.
Missing permanent live for timerThe most frequent cause of a timer fan that runs only while the light is on. If the original installation only ran a switched live and neutral to the fan position — as was common before timer fans became standard — the permanent live needed to power the timer run-on circuit is absent. Remedying this usually involves tracing back to the light switch circuit or a nearby junction box in the ceiling void.
Failed fan motor or internal electronicsFan motors fail — particularly on cheaper units used in high-humidity environments. The motor may have seized, or the internal electronics governing speed, timer or humidistat function may have failed. A fan that hums but doesn't spin usually has a seized motor or capacitor failure. A fan with no response at all, with good supply confirmed at the terminals, has an internal fault and needs replacing.
Steam or water ingress into fittingsBathrooms generate steam — and over time, steam can penetrate any fitting that isn't properly IP-rated or correctly sealed. Water inside a downlight or exhaust grille corrodes contacts, degrades wiring insulation, and eventually causes the fitting to fail entirely. A fitting in zone 1 or 2 without the correct IP rating will fail sooner — often intermittently at first before stopping completely.
Tripped circuit breaker or RCBOA bathroom lighting or fan circuit that has tripped at the consumer unit will take the fan, lights, or both offline depending on whether they're on the same or separate circuits. RCBO trips on bathroom circuits are often caused by water ingress into a fitting — the resulting leakage current to earth is exactly what the RCBO is designed to detect. Resetting without finding the source of ingress will reproduce the trip.
Fan runs all the time and won't stopA fan that runs continuously usually has the permanent live and switched live swapped or bridged — so the fan always sees a live signal. On humidity-controlled fans, a failed humidistat stuck in the closed (call for fan) position produces the same symptom. This is a wiring investigation at the isolator and fan terminals, not a mechanical fault in most cases.
Our Process
How Entigen Diagnoses Bathroom Fan and Light Faults
01
Consumer Unit Check
We check whether the bathroom circuit RCBO or MCB has tripped. If it has, we establish whether the trip was an earth fault (RCBO) or overcurrent (MCB) and investigate accordingly before restoring power.
02
Isolator Check
With power confirmed at the consumer unit, we check for voltage at the supply terminals of the fan isolator. If no supply is present, the fault is upstream. If supply is present but the load terminals show nothing, the isolator has failed internally and needs replacing.
03
Conductor Verification
We confirm the presence and identity of each conductor at the fan connection: permanent live, switched live, and neutral. We check what's actually live under each switching condition. This identifies missing conductors, incorrect connections, and crossed live arrangements that cause the fan to run permanently or not at all.
04
Fan Test
With confirmed correct supply at the fan terminals, we test whether the fan responds. A fan with correct supply and no response has an internal fault. We can often bench-test the fan unit before recommending replacement.
05
Zone Compliance Check
Where we open ceiling voids or inspect fittings, we also note whether fittings in zones 0, 1 or 2 carry the correct IP ratings. Any non-compliant fittings are noted on the report, as they represent both a safety issue and a potential cause of future faults.
When Bathroom Electrical Work Needs Particular Care
- Any electrical fault in a bathroom where water or steam is likely to be involved
- A bathroom RCBO that keeps tripping after reset
- Any fitting in a wet or damp area that has burned, discoloured or failed
- Bathroom electrical work that was not certified at the time of installation
- Shaver sockets, heated towel rail wiring, or shower circuits showing faults
Coverage
We cover Kettering and surrounding Northamptonshire — Barton Seagrave, Burton Latimer, Corby, Wellingborough, Northampton, Earls Barton and surrounding areas.
Related Services
Common Questions
Bathroom Fan & Light FAQs
The most common causes are a failed fan isolator switch, a wiring fault at the isolator or fan terminals, a missing permanent live (needed for timer operation), a failed fan motor or internal electronics, or a tripped circuit breaker. Timer fans need both a switched live and a permanent live — if only a switched live is present, the timer cannot hold the fan on after the light goes off. We test systematically to confirm which of these applies before recommending a fix.
Not every fan installation has the same isolation requirement. The correct arrangement depends on the fan, circuit design, manufacturer’s instructions and the provision required for safe maintenance. Where a fan uses permanent live, switched live and neutral conductors, a suitable three-pole isolator is commonly installed so those conductors can be isolated together for maintenance. The existing installation should be assessed rather than assuming one arrangement applies universally.
Not automatically. A straightforward like-for-like fan replacement, repair or maintenance is generally non-notifiable under Part P. Notification is required where the work includes a new circuit, or an addition or alteration to an existing circuit within the defined special location around a bath or shower. Regardless of notification, the work must comply with Part P and should be safely isolated, inspected and tested, with appropriate certification provided where applicable.
A fan that runs continuously usually has a wiring error at the isolator or fan — the permanent live and switched live have been combined or swapped, so the fan always receives a trigger signal. On humidity-controlled fans, a humidistat stuck in the closed position produces the same symptom. Both require investigation at the fan terminals and isolator to identify which conductors are live under which switching conditions.
BS 7671 divides bathrooms into zones based on proximity to the water source. Zone 0 is inside the bath or shower tray. Zone 1 is directly above the shower or bath to a height of 2.25m. Zone 2 is within 0.6m of zone 1. Each zone requires a minimum IP rating for fittings: typically IP44 for zones 1 and 2. Fitting an accessory without the correct IP rating in these zones is non-compliant and creates a risk of water ingress causing electrical failure or shock hazard.
Fault Support
Related electrical fault help
If your issue sounds similar, these pages may help you understand the fault before getting in touch.
Bathroom Fan or Light Fault in Kettering or Northamptonshire?
We diagnose correctly, work to zone compliance, and certify everything properly. Cost confirmed before attendance.
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