Machine Troubleshooting Guides: Alarms, Faults, and Failure Modes by Category

Key takeaways

• This is the index of every Fabrico machine troubleshooting guide: CNC alarms, drive faults, electrical failures, mechanical wear, fluid power, sensors, and production equipment.
• Every guide follows the same discipline: symptoms first, causes ordered by likelihood, first checks, and safe recovery, with lockout and stored-energy warnings where they matter.
• Exact alarm numbers and fault codes vary by model, series, and firmware. Use these guides for the diagnostic logic, and confirm code meanings in the manufacturer manual.
• The fastest reliability win is not a better repair, it is a better record: log every fault as a downtime event with a cause code so chronic problems earn engineering fixes.

When a machine stops, the clock starts. This index collects all of our troubleshooting guides in one place so maintenance technicians and plant engineers can jump straight to the fault in front of them, whether it is a Fanuc alarm, a tripping overload relay, or a conveyor that will not track.

CNC control alarms

Control alarms tell you which subsystem raised the fault before you open a single cabinet. Start with the guide for your control family:

• FANUC alarm codes: the complete list by family, the reference hub for every FANUC guide below
• Fanuc alarm 401 (VRDY OFF): the servo readiness fault
• Fanuc alarm 414 servo alarm
• Fanuc alarms 500 and 501 (overtravel)
• Fanuc APC alarm 300 (encoder battery)
• Fanuc alarm 750 (spindle serial link)
• Siemens Sinumerik alarm codes
• Mitsubishi CNC alarm codes
• Haas alarm codes

Drive and motor faults

Variable frequency drives and servo systems fail with the same physics across every brand: overcurrent means shorts or jams, overvoltage on deceleration means regeneration, overtemperature means cooling.

• VFD fault codes by vendor and symptom, the reference hub for every drive guide below
• VFD overcurrent faults: the brand-neutral diagnostic logic
• Yaskawa VFD fault codes
• ABB VFD fault codes
• Siemens Sinamics drive fault codes
• Servo motor failure symptoms and testing

Electrical and control hardware

• Allen-Bradley major fault codes
• Siemens S7 PLC SF fault LED
• Contactor and motor starter failure
• Motor overload relay tripping
• Solenoid valve failure and testing

Mechanical wear and motion systems

Mechanical failures announce themselves early in noise, vibration, temperature, and backlash. These guides cover reading those signals and deciding repair versus replace:

• Bearing failure modes and symptoms
• Industrial gearbox failure modes
• Shaft coupling failure modes
• Ball screw wear and backlash diagnosis
• Encoder failure symptoms and testing
• CNC tool changer (ATC) troubleshooting
• Way lube system troubleshooting
• CNC spindle maintenance

Fluid power and plant utilities

Hydraulics, pneumatics, and the utility room fail quietly: pressure sags, moisture creeps in, seals weep. These guides cover the diagnosis:

• Hydraulic pump failure symptoms
• Hydraulic cylinder drift
• Pneumatic system troubleshooting
• Air compressor troubleshooting
• Vacuum pump troubleshooting
• Industrial chiller troubleshooting
• Mechanical seal failure causes

Sensors and automation

• Proximity sensor troubleshooting
• Photoelectric sensor troubleshooting
• Industrial robot fault troubleshooting

Production equipment

• Conveyor belt tracking problems
• Chain conveyor troubleshooting
• MIG welder troubleshooting

How to use these guides

Each guide follows the same structure, because good troubleshooting is a discipline, not a memory test. Read the alarm or symptom precisely and write it down before clearing anything. Work the causes in order of likelihood, cheapest checks first. Respect stored energy: lock out and tag out, verify zero energy, support suspended loads, and never bypass interlocks or safety devices.

One caution applies everywhere: exact code meanings differ by model, series, and firmware. These guides give you the diagnostic logic and the commonly documented patterns; the manufacturer manual for your specific machine is always the final authority.

The habit that beats every individual fix

The plants that stop fighting the same faults share one habit: every stop becomes a data point . Log each fault as a downtime event with a cause code, and track MTBF and MTTR per asset.

A sensor that fails monthly, a coupling that dies every quarter, a chronic low-air alarm: the pattern only becomes visible, and fundable, when it is counted. That is the availability side of what OEE means, and it is where troubleshooting stops being firefighting and becomes reliability engineering.

Where Fabrico fits

Most of the faults in these guides announce themselves as short stops nobody writes down.

Fabrico is a cloud-based MES and OEE platform for manufacturers, with maintenance management (CMMS) built in: it records stops and micro-stops from the machine signal that manual logs miss, and maintenance work orders take each loss from detection to fix, so every fault in this index becomes a counted, categorized event with a repair history.

Read how Fabrico tracks downtime to see it on your own machines.

Frequently asked questions

How do I find the meaning of a specific machine alarm code?

Start with the guide for your control or drive family above to understand the fault category and first checks, then confirm the exact code in the manufacturer's alarm or fault list for your specific model and firmware. Never act on a guessed code meaning.

What is the correct first step when a machine faults?

Record the complete alarm text, code, and axis or device identifier before clearing anything. The alarm history and the fault's context are diagnostic gold, and they disappear with the reset.

When should I stop troubleshooting and call the OEM or a specialist?

When the fix requires opening drive cabinets beyond your qualification, when safety devices are involved, when the fault points to control hardware or firmware, or when a documented recovery procedure requires OEM tooling. A good fault log makes that call cheaper and faster.

Why do the same faults keep coming back after repairs?

Because the repair addressed the symptom, not the cause: the misalignment behind the coupling failure, the contamination behind the valve jam, the undersized air supply behind the pressure faults. Logging every occurrence with a cause code is what exposes those patterns.