What causes FANUC Robot alarm SRVO-015?

Ambient temperature in the controller location exceeds 45°C (113°F). Controller cabinet cooling fan motor not running. Air filter clogged blocking airflow through the controller. Ventilation slots blocked by debris or obstructed by other equipment. Controller main board thermostat fault.

How do I fix FANUC Robot alarm SRVO-015?

1. Check ambient temperature — must be below 45°C (113°F) for normal operation. 2. Verify all cooling fans in the controller are running at full speed. 3. Clean or replace the controller air filter immediately. 4. Ensure ventilation slots on the controller cabinet are not obstructed. 5. IMPORTANT: Perform a complete controller backup before any further troubleshooting. 6. If overheating continues after cooling, the main board may require replacement — contact Fanuc service.

FANUC Robot codes

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FANUC Robot Controller

System · Intermediate · 15-60 minutes

Alarm SRVO-015

Fanuc Robot SRVO-015 - System over heat

SRVO-015 System Over Heat alarm occurs when the R-30iA/R-30iB controller's internal temperature exceeds the critical threshold of 55-60°C, triggering thermal protection circuits. This alarm gives approximately 60 seconds warning before automatic emergency stop (E-STOP) to prevent permanent damage to servo amplifiers, CPU boards, and power supply components. The most common causes are obstructed airflow due to clogged filters or failed cooling fans, followed by excessive ambient temperatures in the controller environment.

FANUC RobotSystemIntermediate15-60 minutes

SRVO-015

Fanuc Robot SRVO-015 - System over heat

System over heat

The controller internal temperature has exceeded the specified limit. The robot will stop within approximately one minute if the temperature is not reduced. This alarm indicates a cooling system failure or excessive ambient temperature.

Root Cause Summary

Safety

Always verify robot is in a safe stopped state before entering the work envelope
Use T1 (low speed) mode when testing after clearing motion or servo alarms

Causes and Fixes

1
Inspect and Replace Air Filter
Open the lower front panel of the controller cabinet and remove the air filter assembly. The filter should be white or light gray; if it appears dark gray or black, it requires immediate replacement. R-30iA/R-30iB use Fanuc part number A05B-0235-C003 (standard filter). Replace every 3-6 months in normal environments, monthly in high-dust applications.
Keep spare filters on-site. In emergency situations, you can temporarily vacuum the existing filter to restore partial airflow, but replace it within 24 hours. Never run the controller without a filter as dust will accumulate on servo amplifier heat sinks.
2
Check Ventilation Clearance
Verify minimum clearance requirements: 300mm (12 inches) on all ventilated sides of the cabinet, 500mm (20 inches) at the rear where exhaust fans are located. Remove any materials, tooling, or equipment stored against the cabinet. Check that cable management has not blocked bottom intake vents.
Never stack materials on top of the controller cabinet or block rear exhaust fans. This can cause overheating within 15-30 minutes of operation under load.
3
Inspect Internal Airflow Path
With the controller powered down and locked out, open the front cabinet door and visually inspect the internal airflow path from bottom intake through the servo amplifier stack to top exhaust. Remove any accumulated dust or debris using compressed air (maximum 40 PSI) or a vacuum. Pay special attention to heat sink fins on servo amplifiers.
Always follow lockout/tagout procedures before opening the controller cabinet. Discharge capacitors may retain lethal voltage for up to 5 minutes after power removal. Wait at least 10 minutes and verify zero voltage before internal work.
4
Verify Servo Amplifier Heat Sink Condition
Examine the heat sink fins on each servo amplifier module. Dust buildup reduces thermal transfer efficiency by 40-60%. Use compressed air to blow out dust between fins, directing airflow from top to bottom to match normal cooling direction. If fins are corroded or damaged, the amplifier requires replacement.
Document the cleanliness state with photos. Establish a preventive maintenance schedule based on your environment: clean heat sinks every 6 months in climate-controlled areas, every 3 months in industrial environments with machining operations nearby.

1
Perform Visual and Auditory Fan Inspection
With the controller powered on (cabinet door open under supervision), visually verify all cooling fans are rotating. Listen for abnormal bearing noise (grinding, squealing, or clicking sounds). Normal fan operation produces steady airflow noise. Check that fan blades are clean and not obstructed by cable ties or wiring.
When inspecting fans with controller powered on, maintain awareness of live high-voltage terminals. Do not touch any internal components. Keep hands and tools away from rotating fan blades.
2
Measure Fan Performance
Using an anemometer, measure exhaust airflow velocity at the rear fan outlets. Normal airflow should be 3.0-4.5 m/s (600-900 FPM) at each fan. Readings below 2.0 m/s indicate degraded fan performance. Compare readings between multiple fans; significant variation indicates a failing fan even if still rotating.
If you don't have an anemometer, hold a tissue paper 50mm from the exhaust fan. It should be strongly pulled toward the fan outlet. Weak or intermittent pull indicates fan failure or obstruction.
3
Check Fan Power Supply Voltage
Using a multimeter, measure DC voltage at the fan connector terminals with the controller powered on. R-30iA/R-30iB cooling fans typically operate at 24VDC. Voltage should be 22-26VDC. Low voltage (below 20VDC) indicates power supply issues. No voltage indicates wiring fault or blown fuse F10 on the CPU board.
Use properly insulated test probes rated for the measurement. Maintain safe distance from adjacent high-voltage components while measuring fan voltage.
4
Replace Failed Cooling Fan
Power down and lock out the controller. Disconnect the fan power connector and remove mounting screws. R-30iA/R-30iB use 120mm x 38mm 24VDC fans, Fanuc part number A05B-2452-J296 (or equivalent Panaflo, NMB, or Sanyo Denki models). Install replacement fan ensuring correct airflow direction (arrow on fan housing). Standard fans have 10,000-hour service life (approximately 14 months continuous operation).
Replace all cooling fans if one fails and the controller is more than 3 years old. Fans from the same production batch typically fail within months of each other. This prevents repeat service calls and downtime.

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