SiteFault-finding guides
Practical fault-finding for motors, drives, sensors, PLCs, hydraulics, air and conveyors.
- Fault-finding guides
Servo drive alarms: where to start
A servo alarm points you somewhere. Sort it into one of six families, ask when it happens, and you'll know where to look before you reach for a spare.
24 October 2026 · 5 min read - Fault-finding guides
Encoder faults on servo systems
Most encoder alarms are the cable, the plug or the screen, not the encoder. Where to look first, and how to avoid swapping a good motor at 3am.
20 October 2026 · 5 min read - Fault-finding guides
Earth faults in control circuits
The control fuse blows after every washdown. How to find an earth fault in a control circuit, and why the second one is the dangerous one.
17 October 2026 · 5 min read - Fault-finding guides
24V DC control supply faults
Half the sensors are out, the PLC keeps rebooting and nothing makes sense. Start with the 24V supply.
14 October 2026 · 5 min read - Fault-finding guides
Contactor chatter and coil faults
A buzzing contactor is a warning. Why contactors chatter, why coils burn out, and why a welded contact is a safety problem as well as a breakdown.
9 October 2026 · 5 min read - Fault-finding guides
Emergency stop circuits that won't reset
Every e-stop on the line is pulled out and the reset still won't take. Where to look, in what order, and the fixes that make a machine dangerous.
7 October 2026 · 5 min read - Fault-finding guides
Safety relays and light curtains: fault-finding safely
The light curtain says blocked and nothing's there. How to find the fault in a safety circuit without leaving the machine less safe than you found it.
3 October 2026 · 6 min read - Fault-finding guides
Going online to a PLC to fault-find
Going online shows you exactly why the machine won't move. It also lets you break it in new ways. How to watch the logic without changing it.
30 September 2026 · 5 min read - Fault-finding guides
The conveyor that won't track, and where to look first
A belt that keeps running off is telling you where the fault is. A fault-finding order for flat belt conveyors, without a hand inside the guard.
26 September 2026 · 6 min read - Fault-finding guides
PLC inputs and outputs: finding the missing signal
The HMI says it's waiting for a signal. Follow it from the field device to the card and back out again, and you'll find where it's gone missing.
23 September 2026 · 5 min read - Fault-finding guides
Photoelectric sensors: alignment, dirt and reflections
Photocells fail in three ways: knocked out of line, dirty, or fooled by something shiny. How to tell which one you've got before the conveyor backs up.
20 September 2026 · 5 min read - Fault-finding guides
Proximity sensors: fault-finding inductive and capacitive sensors
A twenty-pound prox can stop a whole line. How to find out fast if it's the sensor, the target, the cable or the input card.
17 September 2026 · 5 min read - Fault-finding guides
Insulation resistance testing on motors
The motor's tripped and someone wants the spare fitted. Ten minutes with an insulation tester tells you if it's the motor, the cable or neither.
14 September 2026 · 5 min read - Fault-finding guides
Reading drive fault codes when the manual's gone
A four-character code on a drive nobody's seen the manual for. How to work out what it means at 2am, and how to make sure you never have to again.
10 September 2026 · 5 min read - Fault-finding guides
Inverter trips: overcurrent, overvoltage and earth fault
The three drive trips you'll see most, what each one is pointing at, and how to find the cause without killing the drive or yourself.
7 September 2026 · 6 min read - Fault-finding guides
Motor tripping on overload: what to check
An overload that keeps tripping is doing its job. How to find what's loading the motor, and why winding the setting up is the worst fix on site.
4 September 2026 · 5 min read - Fault-finding guides
Three-phase motor won't start: a fault-finding order
Silent, clicking, humming or tripping: what a dead three-phase motor is telling you, and the order to check it in before anyone orders a new one.
1 September 2026 · 6 min read - Fault-finding guides
Half-split fault-finding and why it works
Start in the middle, test, throw half the circuit away. Why half-split beats working from one end, and how to use it on a breakdown.
26 August 2026 · 6 min read
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