SRVO-123

Identify the specific failed fan

Check the alarm detail code suffix (SRVO-123[1], [2], or [3]). Code [1] indicates CPU/slot 1 fan, [2] indicates axis control/slot 2 fan, [3] indicates multiple fans. On teach pendant: MENU > ALARM > F1 [DETAIL] to view full alarm text with fan identifier.

If alarm code shows [3], start diagnostics with the CPU fan as it typically fails first due to higher ambient temperature near the power supply.

Perform visual and auditory inspection

With controller powered ON and cabinet doors open, locate the indicated fan on the backplane (fans are labeled FAN1, FAN2). Listen for grinding, rattling, or bearing noise. Visually confirm blade rotation speed appears slower than other fans. Normal fan speed is approximately 3000-4000 RPM depending on model.

Maintain safe distance from exposed electrical components. Do not insert tools or fingers into rotating fan blades.

Check fan operational hours

Navigate to MENU > SYSTEM > Variables > $FANATIME.$TOTALTIME[x] where x corresponds to fan number. If total runtime exceeds 50,000 hours, bearing wear is highly probable. Compare against maintenance records if available.

Fan lifespan varies significantly based on ambient temperature. Controllers operating above 35°C cabinet temperature may experience fan failure at 30,000-40,000 hours.

Attempt temporary recovery

Power down controller completely (E-stop + main breaker OFF). Wait 60 seconds. Remove fan connector, inspect for corrosion, reconnect firmly. Power up and monitor alarm status. If alarm clears temporarily but returns within hours, bearing failure is confirmed and replacement is required.

Do not operate controller with persistent SRVO-123 for extended periods. Thermal damage to servo amplifiers or CPU may occur, leading to catastrophic failure.

Replace fan motor assembly

Order correct fan assembly using controller serial number (typical part numbers: A290-0324-X501 for 80mm fans, A290-0854-X501 for CPU fans). Power down completely, photograph wiring before disconnection, install new fan matching connector orientation, secure mounting screws to proper torque. Clear alarm history after replacement: MENU > ALARM > [RESET] (F2).

Always replace both fans simultaneously if controller has exceeded 40,000 hours operation. The second fan will likely fail within 6 months, requiring another service call.

Inspect fan blades and housing for debris

Power down controller. Using flashlight, examine fan blades through ventilation openings for dust buildup, coolant residue, or foreign objects. Check intake and exhaust vents on cabinet for blockage. Remove any visible debris carefully.

Ensure main power is OFF and LOTO procedures are followed before accessing internal components.

Clean fan assembly and air filters

Remove cabinet air filters (typically located on door or side panel). Clean reusable filters with compressed air or replace disposable filters. Use compressed air at low pressure (30 PSI max) to blow dust from fan blades while preventing fan from spinning by holding blades gently with non-conductive tool.

Establish preventive maintenance schedule to clean fans and filters every 3-6 months in dusty environments. This single action can extend fan life by 40-60%.

Verify unrestricted cabinet airflow

Ensure minimum 150mm clearance around cabinet ventilation openings. Check that cabinet is not positioned against walls or other equipment blocking airflow. Verify ambient temperature near controller is below 45°C. Use infrared thermometer to check cabinet internal temperature at CPU and axis control boards.

If cabinet temperature exceeds 40°C, consider adding supplemental cooling fans or relocating controller to cooler environment before fan replacement.

Test fan speed after cleaning

Power up controller and monitor alarm status. Navigate to MENU > SYSTEM > Variables > $FANATIME.$FANSPD[x] to view current fan speed percentage (should read 90-100% after cleaning). If speed remains below 80%, mechanical failure is indicated despite cleaning.

Document baseline fan speed values when controller is new or after fan replacement for future diagnostic reference.

Inspect fan connector and wiring harness

Power down controller completely. Locate fan connector on backplane (typically 3-pin or 4-pin Molex-style). Disconnect and inspect pins for corrosion, discoloration, or physical damage. Check wire harness routing for pinch points, excessive bending near connectors, or insulation damage.

Document connector orientation and wire colors with photograph before disconnection to ensure correct reassembly.

Measure fan motor electrical parameters

With fan disconnected, use multimeter to measure resistance across fan motor terminals (typically 20-100 ohms for DC fans). Measure tachometer signal wire continuity to backplane. Compare values against specifications in controller maintenance manual section 3.4.2 (fan specifications).

If resistance is infinite (open circuit) or near zero (short circuit), internal motor coil failure is confirmed. If resistance is normal but alarm persists, suspect backplane fan monitoring circuit failure.