Fault library
Describe the symptom, then narrow by category, difficulty or risk.
185 results
Contactor has voltage at the coil but won't pull in
You measure the rated control voltage (e.g. 24V) across the coil terminals, but the contactor refuses to energise — no clunk, no pull-in, contacts stay open.
Contactor chattering or buzzing instead of holding in
The contactor rapidly clicks/buzzes, pulls in and drops out repeatedly, or hums loudly without seating cleanly. Often comes with arcing noise and heat.
Contactor contacts welded closed — load won't switch off
The contactor won't drop out when the coil is de-energised. The load stays powered even with the control circuit off, because the main contacts have welded together.
Control relay coil not energising
A plug-in or interface relay isn't picking up — its indicator stays off and its contacts don't change, so whatever it controls never operates.
Auxiliary contact not making — seal-in or interlock fails
The contactor pulls in, but an auxiliary contact (used for seal-in, interlock, or status) doesn't change state, so the circuit won't latch, an interlock misbehaves, or status feedback is wrong.
Contactor drops out on its own / won't stay latched
The contactor pulls in when you press start but drops out the moment you release the button, or randomly during running — the seal-in (latch) isn't holding it.
Overload relay won't reset
After an overload trip, the reset won't take — the starter won't re-arm, or it resets and trips straight back. The control circuit stays broken at the overload's contact.
Contactor coil overheating / burning smell
The contactor coil runs hot, discolours, or gives off a burning smell, and may eventually fail. It might still operate for now but won't last.
Star-delta starter not transitioning to delta
A star-delta (wye-delta) starter starts the motor in star but never switches to delta — the motor runs weak/slow, or trips, because it stays in the starting connection.
Latching / impulse relay stuck in one state
A latching (impulse) relay won't change state on a pulse — lighting or a load stays on or off regardless of the switch, because the relay isn't toggling.
Phase-failure / monitoring relay has tripped the circuit
A phase-failure or phase-sequence monitoring relay has dropped out and is holding the control circuit off, stopping the equipment — even though the panel looks powered.
Motor overload keeps tripping
The thermal/electronic overload trips repeatedly, either on start or after the motor has run for a while. Resetting only buys you a short run before it trips again.
Motor goes one way but won't go the other (e.g. down but not up)
A reversing drive works in one direction only. One command (say, down) runs fine; the other (up) does nothing, or just hums/trips. Common on hoists, doors, and conveyors.
Motor won't start and makes no sound at all
Press start and nothing happens — no hum, no movement, no attempt to turn. The motor is completely dead rather than struggling.
Motor hums but won't start to turn
On start the motor hums or buzzes but won't rotate — it may draw heavy current and trip protection. Often a sign it's only getting two phases or is mechanically locked.
Motor running hot / overheating
The motor runs but gets excessively hot — too hot to touch, smell of hot insulation, or thermal protection cutting in after a while.
Motor noisy or vibrating (bearing / mechanical)
The motor runs but is noisy, rough, or vibrating — grinding, rumbling, or whining noises that point to bearings or mechanical trouble.
Motor with low insulation resistance to earth
An insulation resistance test on the motor reads low to earth — a sign the winding insulation is degraded, damp, or contaminated, risking trips and failure.
Soft starter faulting or not ramping the motor
A soft starter won't ramp the motor up smoothly — it faults out, the motor jerks or doesn't reach full speed, or the bypass doesn't engage.
Motor trips protection on start but runs fine if it gets going
Protection trips during the start/inrush, but on the rare occasion it gets running it's fine — pointing at starting current, settings, or load inertia rather than a running fault.
Motor runs in the wrong direction
The motor runs but the wrong way — pump runs backwards, fan blows the wrong way, conveyor reverses. Usually a phase-rotation issue after wiring or supply work.
Motor draws fluctuating current / unstable running
The motor runs but its current swings up and down, speed surges, or it runs roughly — pointing at load variation, supply, or control instability rather than a hard fault.
Reversing starter trips when changing direction
The drive runs each direction on its own but trips protection when you change from forward to reverse (or vice versa), often if the changeover is too quick.
Forward/reverse interlock locking out both directions
Neither direction will run — the interlock that stops both contactors closing together appears to be holding everything off, so no movement at all.
Reversing circuit runs the same direction both ways
Selecting forward or reverse both turn the motor the same way — the direction never actually changes, even though both contactors operate.
Jog / inch function not working
The jog (inch) control doesn't move the motor in short bursts — pressing jog does nothing, or it latches and runs continuously instead of jogging.
Travel limit stops a direction too early
The drive stops short in one direction — a travel limit is operating before the load reaches the proper end position, cutting the movement off early.
VSD/drive ignores the direction command
A drive runs but only one way — the reverse (or forward) command is ignored, even though the drive is running and the motor turns.
VSD powered up but won't start the motor
The drive is energised and the display is alive, but it won't run the motor. No fault may be shown — it just sits in 'ready' or 'stopped' and ignores the start command.
VSD trips on overcurrent / overload
The drive trips with an overcurrent or overload code — on start, on acceleration, or under running load. It may restart and trip again on the same point in the cycle.
VSD trips on DC bus overvoltage
The drive trips on overvoltage — usually during deceleration or stopping, when a spinning load pushes energy back into the DC bus faster than it can be absorbed.
VSD trips on undervoltage / loses supply
The drive trips on undervoltage — the DC bus drops too low, often on start, under load, or with supply dips, and the drive shuts down to protect itself.
VSD trips on over-temperature
The drive trips on over-temperature — usually after running a while, in hot conditions, or under heavy load, because it can't shed heat fast enough.
VSD trips on earth/ground fault
The drive trips with an earth/ground-fault code — typically the instant it outputs — indicating leakage to earth on the motor or output cabling.
VSD runs but motor doesn't reach set speed
The drive shows it's running and outputting, but the motor turns slowly, sluggishly, or never reaches the commanded speed.
VSD display blank / drive appears dead
The drive's display is blank and it shows no signs of life — no keypad, no LEDs — so nothing can be operated or diagnosed from the panel.
VSD communication / fieldbus fault
The drive has lost communication with the PLC/SCADA over its fieldbus (e.g. control by network) — comms-loss fault, no remote control, or the drive stops on comms timeout.
VSD nuisance tripping with no obvious cause
The drive trips intermittently with codes that don't seem to match the conditions — random faults, hard to reproduce, often noise- or connection-related.
Motor noisy or whining when run on a VSD
The motor runs but is noticeably noisy on the drive — a whine, whistle, or growl that isn't there on direct supply, sometimes worse at certain speeds.
PLC output LED is on but the device doesn't work
The PLC output indicator says the output is energised, but the connected device (valve, contactor, lamp, motor starter) does nothing. The program thinks everything is fine.
PLC input not reading despite a signal present
A field device is clearly providing a signal, but the PLC input bit/LED doesn't come on — the program never sees the input, so logic that depends on it won't run.
PLC I/O module faulted / showing module error
An I/O module shows a fault LED or the controller reports a module error — a whole block of inputs/outputs is dead or unreliable, not just one channel.
PLC communication fault (network / remote I/O)
The PLC has lost communication with a device, remote I/O, HMI, or network — comms-fault indication, missing data, or remote I/O dropping out.
PLC output stuck on (device won't switch off)
A field device stays energised even though the program has turned the output off — the output won't release, so the device runs continuously.
PLC in fault / stop mode (not running the program)
The PLC has stopped running its program — a fault LED is on or it's in STOP/PROG mode — so no I/O is being controlled and the machine is dead in a defined way.
PLC analogue output not driving correctly
A PLC analogue output (to a valve positioner, VSD reference, etc.) isn't producing the right signal — the device doesn't follow the command, or the output sits at zero/full scale.
HMI / touchscreen blank or frozen
The operator HMI/touchscreen is blank, frozen, or unresponsive — operators can't see status or control the machine, even though the PLC may still be running.
PLC output fuse keeps blowing
The fuse protecting a PLC output (or output group) blows repeatedly — knocking out one or several outputs each time it goes.
Timer relay not switching its output
A timer relay is powered but its output contact never changes state — the delayed action (start, changeover, stop) never happens, or it switches at the wrong time.
Timer times out too long or too short
The timer switches, but at the wrong time — the delay is much longer or shorter than it should be, throwing out the sequence.
Timer resets part-way through timing
The timer starts but resets before it finishes, so it never completes — the delayed action keeps getting cancelled and never happens.
Timer output chatters or pulses at changeover
When the timer reaches its set point, the output chatters or pulses instead of switching cleanly, causing the downstream device to buzz or operate erratically.
Timer completely dead (no power / no display)
The timer shows no signs of life — no display, no LED, no output activity — so nothing it controls will ever operate.
Timer behaving as the wrong type (on-delay vs off-delay)
The timer switches at the wrong point in the sequence because it's acting as the wrong function — on-delay where off-delay is needed, single-shot where cyclic is needed, and so on.
Limit switch or proximity sensor not being detected
A limit switch or proximity/photo sensor isn't registering — the machine doesn't stop at position, the input never makes, or the sensor LED looks wrong for the target's position.
Proximity sensor permanently on (always made)
A proximity sensor reads 'detected' all the time — its output stays on even with no target present, so the controller always sees the input made.
Sensor intermittent / drops out randomly
A sensor works most of the time but drops out or false-triggers intermittently, causing random stops, miscounts, or sequence faults that are hard to pin down.
Photoelectric sensor not detecting
A photo-eye (through-beam, retro-reflective, or diffuse) isn't detecting reliably — it misses the target, or the output doesn't change when something blocks/enters the beam.
Limit switch stuck made (won't release)
A mechanical limit switch stays operated even after the actuator leaves it — the input stays made, so the machine thinks it's still at that limit.
Analogue sensor (4-20mA / 0-10V) reading wrong
An analogue sensor (pressure, level, temperature) gives a wrong or fixed reading — stuck at zero, pinned at full scale, or simply not matching reality.
Encoder feedback fault (position/speed wrong)
Position or speed feedback from an encoder is wrong — counts drift, position is lost, or a drive faults on encoder loss, so motion control misbehaves.
Safety light curtain keeps tripping the machine
A safety light curtain is stopping or preventing the machine from running — it shows blocked/faulted even when the access area looks clear.
Float / level switch not operating
A float or level switch isn't controlling correctly — a pump won't start/stop on level, a tank overfills or runs dry, because the level switch isn't changing state.
Heater bank drawing uneven current across phases
A multi-element heater bank pulls noticeably different current on each phase. Heating is uneven, output is low, or a phase reads much lower than the others.
Solid-state relay (SSR) stuck on — heat won't switch off
A heater (or other SSR-driven load) stays on even when the controller commands it off. Temperature overshoots, or the load runs continuously regardless of the control signal.
Heater not heating at all
A heater (element, band, or bank) produces no heat — temperature won't rise, the process stays cold, despite the control calling for heat.
SSR not switching on (load won't energise)
A solid-state relay won't turn its load on even when commanded — the heater/load stays off because the SSR isn't conducting.
Heater overshooting or oscillating around setpoint
The process temperature overshoots the setpoint then cycles above and below it, instead of settling — poor control that can spoil product or trip high-limits.
Thermocouple open or reversed (wrong temperature reading)
A thermocouple gives a wrong temperature — reads way off, shows an open/sensor-break, or moves the wrong way — so the heat control can't work properly.
Heater tripping the RCD / earth leakage
A heater circuit trips its RCD/earth-leakage protection — often when cold and first switched on, or once it's been damp — pointing to leakage to earth from the element.
Band / cartridge heater burnt out or underperforming
A band or cartridge heater (e.g. on a barrel or die) isn't reaching temperature or has failed — one zone stays cold or lags while others are fine.
RCD / RCBO keeps tripping
An RCD or RCBO trips repeatedly — immediately on reset, randomly during the day, or only when certain equipment runs. The earth-leakage protection is doing its job; something is leaking.
RCD trips only in wet weather or after wash-down
The RCD holds fine when dry but trips after rain, washdown, or in damp conditions — pointing to moisture creating an earth-leakage path somewhere outdoors or in wet areas.
RCD won't reset at all
The RCD won't stay reset — the toggle won't latch up, or it trips instantly every time, so the circuit can't be restored.
RCD nuisance tripping with lots of electronics
An RCD trips intermittently with no single faulty appliance — typically where many electronic devices (with filters/SMPS) share one RCD, each adding a little standing leakage.
RCD test button doesn't trip the RCD
Pressing the RCD's test button doesn't trip it — a serious sign the RCD may not operate on a real earth fault, even though the circuit is live and working.
RCBO tripping — telling overload from earth leakage
An RCBO (combined RCD + MCB) keeps tripping and you need to know whether it's tripping on overcurrent/overload or on earth leakage — the fix is very different for each.
RCD trips the moment a specific load is switched on
The RCD is fine until a particular appliance/circuit is switched on, then it trips immediately — clearly pointing at that load or its switch-on behaviour.
RCD passes test but doesn't trip on a real leakage test
The RCD's own button trips it, but a proper instrument test shows it doesn't trip within the required time/current — so it may not protect adequately in a real fault.
No control voltage in the panel
Nothing in the control circuit will operate — contactors won't pull in, indicators are dead, the PLC may be off. The control voltage that should be there simply isn't.
Three-phase equipment single-phasing (lost a phase)
Three-phase equipment is misbehaving — motors humming, struggling, overheating, or tripping — because one phase has been lost somewhere between the supply and the load.
E-stop circuit won't reset / machine won't start
The machine won't start because the emergency-stop circuit won't reset — the safety relay stays dropped out, holding everything off, even with all e-stops apparently released.
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.
Intermittent fault that's hard to reproduce
Something fails occasionally — random trips, dropouts, or stoppages — but works fine when you go to look at it. The classic 'can't fault it on the bench' problem.
Voltage drop on a long cable run
Equipment at the end of a long run misbehaves — dim lights, a contactor that won't hold, a motor struggling — because volt-drop along the cable leaves too little voltage at the load.
Loose connection overheating (discolouration / smell)
A terminal or connection is overheating — discoloured insulation, a burning smell, or heat you can feel — a common cause of nuisance faults and a real fire risk.
Lost or high-resistance neutral
Strange symptoms across a circuit or installation — voltages going high and low on different loads, flickering, equipment damage — pointing to a lost or high-resistance neutral.
Whole circuit / board nuisance tripping
A whole circuit or board protective device trips intermittently with no obvious single cause — affecting several loads — and you need a systematic way to corner it.
No supply at a socket-outlet or point
A socket-outlet or point is dead — nothing plugged in works — while other points may be fine. A bread-and-butter 'trace it back' fault.
Time clock / programmable timer not switching its load
A time clock (lighting, heating, ventilation) isn't switching at the programmed times — the load stays on or off regardless of the schedule.
Contactor noisy only when the load is connected
The contactor pulls in and holds quietly with no load, but buzzes or hums once the load is connected and drawing current.
Two-speed motor won't change speed
A two-speed (e.g. Dahlander or two-winding) motor runs on one speed but won't switch to the other — the speed-change contactors or windings aren't doing their job.
Pump motor runs but there's no flow
The pump motor runs normally electrically, but there's little or no flow/pressure — the electrics are fine, so the problem is hydraulic, priming, or direction.
VSD reports output phase loss / motor phase loss
The drive trips or warns of an output (motor) phase loss — it isn't seeing balanced current on all three output phases to the motor.
PLC output flickering / device chattering
A PLC output rapidly switches on and off, making the connected device (contactor, valve, lamp) chatter or flicker instead of staying in a steady state.
Proximity sensor triggering at the wrong distance
A proximity sensor detects, but at the wrong point — too early, too late, or inconsistently — so positioning or counting is off even though the sensor 'works'.
Immersion / tank heater not working
An immersion or tank heater isn't heating the water/fluid — it stays cold despite the thermostat calling, or trips its protection.
RCD trips randomly with no obvious pattern
An RCD trips occasionally with nothing obviously changing — not tied to a clear appliance, weather, or time — the frustrating 'tripped again overnight' type.
Equipment tripping the supply on startup surge
Switching on a piece of equipment trips an upstream breaker or causes a momentary dip — the inrush/startup surge is exceeding what the protection or supply can ride through.
Control relay contacts sticking or welded
A control/interface relay's contacts stick closed (or won't make cleanly) — the controlled circuit stays on when it should be off, or switches unreliably.
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.
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.
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.
Dimmer buzzing or LEDs not dimming smoothly
A dimmer buzzes, the LEDs flicker/strobe at low levels, won't go very low, or some lamps glow when 'off' — typically an LED/dimmer compatibility issue.
Fluorescent light not starting or flickering
A fluorescent tube won't strike, flickers, or glows only at the ends — common in older garages, laundries, and sheds.
All lights in one area out (others fine)
Every light in one part of the house is dead while power points and other lighting still work — points at that lighting circuit's protective device or a shared fault.
LED lights glowing faintly when switched off
LED lamps glow dimly or pulse even after the switch is off — unsettling but usually a small leakage/induced-voltage effect rather than a dangerous fault.
Motion-sensor light not working correctly
A sensor (PIR) light won't come on, stays on permanently, or triggers at the wrong times — common on eaves, garages, and entries.
Power point (GPO) completely dead
Nothing plugged into a power point works, while other outlets are fine. A classic trace-it-back fault on a single GPO or the run feeding it.
Half the power points in the house not working
A group of outlets across several rooms is dead together while lights and other GPOs work — points at one power circuit's protection or a shared upstream fault.
Double power point — one side works, one doesn't
On a double GPO, one socket works and the other is dead — usually an internal fault in the outlet or a loose link between the two sockets.
Power point burnt, melted, or smells hot
A GPO is discoloured, melted, or gives off a burning smell — a serious fire-risk fault from arcing/overheating at the outlet, usually from a poor plug fit or overload.
USB power point not charging devices
A GPO with built-in USB ports won't charge (or charges very slowly) while the normal sockets work — usually the USB module or a device/cable mismatch.
Powerboard or extension lead not working
A powerboard or extension lead delivers no power, while the wall outlet it's plugged into is fine — usually the board's switch, its overload/reset, or a damaged lead.
An appliance trips the power the moment it's plugged in or switched on
Plugging in or switching on a particular appliance instantly trips the safety switch or breaker — strongly suggesting an earth fault or short in that appliance.
Smart switch not working (no neutral at the switch)
A smart/Wi-Fi switch won't power up, drops offline, or makes the light glow/flicker — commonly because there's no neutral at the switch, which many smart switches need.
Safety switch (RCD) keeps tripping at the switchboard
The safety switch trips repeatedly — instantly on reset, randomly, or when certain appliances run. It's detecting earth leakage somewhere; the job is to find where.
Safety switch won't reset
The safety switch won't stay up when you try to reset it — power can't be restored because a fault is still present (or the device/wiring is at fault).
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.
No power to the whole house
The entire home has no power — nothing works. Could be a supply outage, the main switch/main safety switch, or a main fault, and the first job is to tell which.
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.
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.
No hot water (electric storage system)
An electric storage hot water system has gone cold — no hot water at the taps. Usually the element, thermostat, supply, or (for off-peak) the tariff/timing.
Hot water runs out too quickly / not hot enough
There's some hot water but it runs out fast or never gets properly hot — often a partially-failed element, a thermostat set low, or a system being asked to do more than its size.
Off-peak / controlled-load hot water not heating
A controlled-load (off-peak) hot water system isn't being energised during its tariff window — the element and thermostat may be fine, but power never arrives at the right time.
Hot water system tripping the safety switch
The hot water system trips the safety switch — typically when it heats — pointing at an element leaking to earth or moisture in the system.
Instantaneous / heat-pump hot water — no power or fault light
An instantaneous electric or heat-pump hot water unit shows no power or a fault indicator and isn't heating — different from a simple storage element fault.
Electric wall/panel heater not working
A fixed electric heater (panel, wall, or in-slab) isn't heating — no warmth despite being switched on, pointing at the element, thermostat, controller, or supply.
Electric oven not heating
The oven powers up (light/clock may work) but doesn't get hot — pointing at the element, thermostat, or the oven's controls rather than the supply.
Oven trips the power when switched on or heating
Turning the oven on (or selecting heat/grill) trips the safety switch or breaker — usually an element that's failed to earth.
Cooktop element (radiant/coil) not working
One element/zone on an electric (radiant or coil) cooktop isn't heating while others work — pointing at that element, its switch/control, or connection.
Induction cooktop showing a fault or not heating
An induction cooktop won't heat, shows an error code, or doesn't recognise pans — different from a radiant element fault because it's electronic and pan-dependent.
Rangehood fan or light not working
A rangehood's fan won't run or its light is out — could be the supply, switches, motor, or (for ducted units) the controls.
Oven clock/controls blank but oven otherwise has power
The oven's clock/display is blank or the touch controls are unresponsive, often preventing the oven from operating even though the circuit is live.
Ceiling fan not working
A ceiling fan won't run (light may still work, or not) — pointing at the wall control/remote, the capacitor, the motor, or the supply.
Ceiling fan noisy, wobbling, or running slow
A ceiling fan runs but wobbles, clicks/hums, or only runs slowly — usually balance/mounting, a tired capacitor, or controller issues.
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.
Fan only runs on one speed or wrong speed
A multi-speed fan is stuck on one speed, or the speeds don't match the control — usually the speed controller, capacitor, or wiring.
Smoke alarm chirping / beeping intermittently
A smoke alarm chirps every minute or so — the classic low-battery or end-of-life signal, but can also be dust or a backup-battery issue on mains alarms.
Smoke alarm going off for no reason (false alarms)
A smoke alarm sounds with no fire — often from cooking/steam, dust/insects, location, or an aging alarm. Must be resolved without disabling the alarm.
Interconnected smoke alarms all sounding / not interconnecting
Interconnected alarms all sound when one triggers (by design), but you need to find which one, or they aren't interconnecting when they should — a wiring/wireless link issue.
Mains (hardwired) smoke alarm not working / no light
A hardwired smoke alarm's power indicator is off or it isn't functioning — points at the alarm's supply (often a lighting circuit), the alarm itself, or end of life.
Outdoor power point not working
An outdoor GPO is dead — often after rain — pointing at a tripped safety switch from moisture, a weatherproofing failure, or the outlet/run.
Outdoor / garden light not working
An outdoor or garden light is out — could be the lamp, a sensor/timer, weatherproofing/water ingress, or the supply.
No power to a shed or outbuilding
A shed or outbuilding has lost power — points at the sub-circuit/sub-board feeding it, the submain, a tripped protective device, or moisture.
Pool or spa equipment tripping the power
A pool/spa pump, heater, or chlorinator trips the safety switch — a high-risk wet-area fault that needs the leakage found, never bypassed.
Garden irrigation / pump controller not working
An irrigation controller or garden pump won't run the zones/pump — points at the controller power, the solenoids/pump supply, or wiring in a wet outdoor environment.
Doorbell or intercom not working
A wired doorbell or intercom doesn't chime/respond — points at the button, the transformer/supply, the chime/unit, or the wiring.
Three-phase distribution board badly unbalanced
One phase of a three-phase board runs much hotter / higher current than the others — nuisance tripping on that phase, a hot neutral, or a warm phase conductor at the board.
Sub-main keeps tripping the main board
A sub-board's incoming protective device (or the main feeding it) trips — taking out everything downstream — and you need to tell overload from a fault on the sub-main or sub-board.
Busbar or board connection running hot
A busbar joint, incomer, or board connection runs hot / discoloured — a high-energy fire-risk fault on a distribution board that must be addressed quickly.
Main switch / incomer not making on all phases
A board's main switch or incomer isn't passing all phases — downstream gets partial supply (single-phasing) or nothing — pointing at the switch contacts or its terminations.
Distribution board circuits mislabelled / wrong breaker isolates wrong circuit
Switching off a labelled breaker doesn't isolate the expected circuit (or isolates the wrong one) — a schedule/labelling problem that's a real safety hazard for anyone relying on it.
Three-phase supply voltage high, low, or unbalanced
Measured supply voltages are out of the expected range or unbalanced between phases — causing equipment trips, poor performance, or protection operating across the board.
Surge protection device (SPD) showing a fault / end of life
A board-mounted surge protective device shows a fault indicator (window changed colour / flag) — it has likely reached end of life after absorbing surges and no longer protects.
Large motor start trips the distribution board
Starting a large three-phase motor (lift, pump, compressor, aircon) trips the board feeding it or dips the supply — an inrush/coordination issue rather than a running fault.
Exit sign not illuminated
An illuminated exit sign is dark — it may have lost supply, failed its lamp/LED, or have a faulty driver. A life-safety fitting that must be kept working.
Emergency light fails its discharge test
An emergency fitting works on mains but won't stay lit for the required duration when tested (mains removed) — usually a failed/aged battery, but can be charging or lamp issues.
Emergency light stays on / won't go back to normal
An emergency fitting stays in emergency (battery) mode or its charge/fault LED stays wrong even with normal supply present — pointing at the supply sensing, charging, or the fitting.
Emergency lighting circuit tripping / dead
A whole emergency lighting circuit is dead or its protective device trips — taking multiple life-safety fittings out at once, which must be restored quickly.
Automatic emergency-light test system reporting faults
An addressable / automatic emergency-lighting test system is flagging faults or losing communication with fittings — common in larger commercial buildings.
Emergency light charge indicator off (not charging)
An emergency fitting's charge indicator (usually a small LED) is off, meaning the battery isn't charging — it will then fail when tested or in a real outage.
Maintained/non-maintained emergency fitting behaving wrong
An emergency fitting is in the wrong mode — a maintained fitting that should stay lit is off in normal use, or a non-maintained one is on all the time — usually a wiring/configuration issue.
Data outlet has no link / no network
A device plugged into a data outlet gets no link or no network, while others work — pointing at the patch lead, the outlet termination, the cable run, or the patch panel/switch port.
Data cabling run fails certification / wiremap fault
A structured cabling run fails a tester (wiremap fault, open, short, split pair, or excessive length) — so it won't reliably carry the network even if a link sometimes appears.
PoE device (camera/AP/phone) not powering up
A Power-over-Ethernet device (IP camera, wireless AP, VoIP phone) won't power on over its data cable — pointing at the PoE source, the budget, the cable, or the device's PoE class.
Data connection slow, dropping, or unreliable
A data point links but is slow, drops out, or negotiates a low speed — pointing at cabling quality, a marginal termination, interference, or the run length, rather than a hard break.
Phone/analogue line dead (no dial tone)
An analogue phone/fax/EFTPOS line is dead — no dial tone — pointing at the line in, the socket/wiring, or the device, in premises that still use copper voice services.
TV antenna outlet — no or poor signal
A TV outlet has no signal or poor/pixelating picture while others are fine — pointing at the outlet/lead, a splitter/amplifier, cabling, or the antenna/head-end.
Split-system air-con not running at all
A split-system (head unit + outdoor condenser) is completely dead — no response from the remote/controller — pointing at supply, isolator, controller, or the indoor PCB.
Air-con tripping the power
An air-con unit trips its breaker or safety switch — on start, when the compressor kicks in, or randomly — pointing at the compressor, an earth fault, or the supply/protection.
Air-con runs but isn't cooling (electrical checks)
The unit runs (fan blows) but doesn't cool — from an electrical standpoint, checking whether the compressor/outdoor unit is actually being commanded and powered before handing to refrigeration.
Ducted air-con system has no power / won't start
A ducted system (roof/cupboard fan unit + zones/controller) is dead or won't start — pointing at the dedicated supply/isolator, the controller, zone motors, or the unit's PCB.
Air-con condensate pump not working / unit shut down on overflow
An aircon has shut down on a condensate overflow/float switch, or its condensate pump isn't running — water isn't being removed, so the unit stops to prevent overflow.
HVAC thermostat/controller blank or unresponsive
A heating/cooling thermostat or controller is blank or unresponsive, so the system won't run — pointing at the controller's power (often low-voltage from the unit), wiring, or the controller itself.
Commercial exhaust / ventilation fan not running
A larger exhaust/ventilation fan (carpark, kitchen, plant room) won't run — pointing at its starter/control, supply, motor, or an interlock with a control system.
LED batten / panel flickering or strobing
An LED batten or panel (garage, office, retail) flickers, strobes, or won't switch off cleanly — common with cheaper fittings, sensors, or shared neutrals.
High-bay or floodlight not working / cutting out
A high-bay (warehouse) or floodlight is out or cuts out after warming up — pointing at the driver, heat, supply, or a daylight/photocell control.
Three-phase outlet / appliance not working (one phase missing)
A three-phase outlet or appliance (welder, large machine, commercial kitchen gear) isn't working right — a missing phase at the socket leaves it under-powered or not starting.
Commercial kitchen equipment has no power
A piece of commercial kitchen gear (oven, fryer, dishwasher, cool room) is dead — pointing at its dedicated circuit, isolator, an emergency-stop/gas-interlock, or the appliance.
Off-peak / controlled-load contactor not switching
The contactor that switches a controlled-load (off-peak) supply — for hot water, slab heating, or pool gear — isn't operating in its window, so the load never gets power.
Safety switch trips only at night / at a set time
A safety switch trips at a consistent time (often overnight) — pointing at a time-controlled load (off-peak hot water, slab heating, irrigation, pool) with an earth-leakage fault that only runs then.
Safety switch trips during storms / lightning activity
A safety switch trips during thunderstorms/lightning — usually transient surges or moisture, sometimes a marginal install — and it's about telling a transient nuisance from a real fault.
Three-phase equipment running hot from supply imbalance
Three-phase equipment (motors, heaters, large gear) runs hotter than expected or nuisance-trips, traced to a voltage/current imbalance between phases rather than the equipment itself.
High earth-fault loop impedance / earthing concern
Testing shows a high earth-fault loop impedance (or an earthing concern) on a circuit — meaning protection might not operate fast enough on a fault, which is a safety issue to resolve.