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FANUC Robot Controller
Servo/Axis · Intermediate · 15-60 minutes
Fanuc Robot SRVO-067 - OHAL2 alarm (pulsecoder overtemp)
SRVO-067 OHAL2 alarm indicates the pulse coder (encoder) internal thermostat has tripped due to excessive temperature at the specified axis. This is a protective mechanism to prevent permanent encoder damage from overheating caused by sustained mechanical overload, poor heat dissipation, or adverse environmental conditions. The encoder temperature limit is typically 90-95°C, and the thermostat will not reset until the component has adequately cooled.
SRVO-067
Fanuc Robot SRVO-067 - OHAL2 alarm (pulsecoder overtemp)
OHAL2 alarm (pulsecoder overtemp)
The temperature inside the pulse coder on the specified axis has exceeded the limit, causing the built-in thermostat to activate. The encoder is overheating.
Root Cause Summary
SRVO-067 OHAL2 alarm indicates the pulse coder (encoder) internal thermostat has tripped due to excessive temperature at the specified axis. This is a protective mechanism to prevent permanent encoder damage from overheating caused by sustained mechanical overload, poor heat dissipation, or adverse environmental conditions. The encoder temperature limit is typically 90-95°C, and the thermostat will not reset until the component has adequately cooled.
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
Verify alarm axis and allow cooling period
Note the axis number from the alarm detail. Power off the robot and wait minimum 30-60 minutes for complete thermal equalization. Do not attempt to reset the alarm immediately as the thermostat is a physical bi-metallic switch that requires actual temperature drop to reset.
Do not force-cool the joint with compressed air or liquids as thermal shock can damage encoder components and seals.
- 2
Check payload configuration and actual load
Navigate to MENU > SETUP > Payload on teach pendant. Verify payload settings match actual tooling and workpiece weight. Check $PAYLOADS system variable for all configured payloads. Incorrect payload settings cause torque miscalculations and potential overload conditions.
Use the Payload Identification function (MENU > SETUP > Payload > [OTHER] > Payload ID) to automatically measure actual payload if you suspect configuration mismatch.
- 3
Review servo load data for affected axis
Access MENU > NEXT > SYSTEM > MASTER/CAL > Servo Monitor. Select the affected axis and observe Torque (%) and Current (%). Review peak values during typical program execution. Sustained loads above 70% or peaks above 85% indicate mechanical problems or excessive application demands.
Enable servo load recording via $SCR.$LOAD_MONITOR and review historical data to identify specific motion segments causing high loads.
- 4
Inspect for mechanical binding or interference
Manually jog the affected axis at low speed (5-10%) through its full range of motion. Listen for unusual noise, grinding, or resistance. Check for cable interference, foreign material in the joint area, or harness binding. Verify brake release on the affected axis if equipped.
Enable deadman switch and use LOW speed mode when jogging to inspect mechanical issues. Position personnel clear of robot motion path.
- 5
Examine duty cycle and motion programming
Review robot program for continuous high-speed operation without dwell periods. Check motion termination types—CNT (continuous) motions at high speed generate more heat than FINE terminations. Consider reducing speed overrides or adding brief delays in cyclic operations to allow thermal dissipation.
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