FANUC SRVO-062 BZAL Alarm: Pulsecoder Battery Zero
What SRVO-062 BZAL Means
The FANUC controller displays this fault as SERVO-062 BZAL alarm (Group: i Axis: j), with the group and axis numbers identifying exactly which motor and pulsecoder triggered it. BZAL stands for battery-zero alarm: the controller has detected that the backup battery supplying the pulsecoder’s absolute-position memory is empty, disconnected, or not connected at all.
When SRVO-062 trips, the robot faults out and servo power drops on the affected axis. The pulsecoder can no longer confirm that its stored absolute-position count is valid, so the controller treats the position data for that axis as suspect. The robot will not run in AUTO until the alarm is cleared, the cause is corrected, and — if position data was actually lost — the axis is remastered.
Common Causes Of The BZAL Alarm
Most SRVO-062 BZAL alarms come from a simple, low-cost problem before they come from a real pulsecoder failure. Check in this order: a battery discharged past its usable life, which is by far the most common cause, especially on robots that have sat powered down; a battery cable broken, pinched, or disconnected inside the robot base or arm, often from prior maintenance work; a loose or corroded battery connector at the battery box or axis junction; a damaged wiring harness with an intermittent open circuit or short to ground; and, less often, a pulsecoder or integrated motor encoder that cannot hold or report absolute-position data even with a good battery installed.
Related alarms on the same fault path:
- SRVO-065 BLAL — low-battery warning; the battery is weak but not yet empty, and it usually precedes SRVO-062 if the battery is not replaced in time.
- SRVO-075 Pulse not established — the absolute position for that axis cannot be established, and it commonly appears right after SRVO-062 once position data has already been lost.
Troubleshooting Steps For SRVO-062
Work through the fault methodically and record what you find before clearing anything:
- Record the full alarm text, group, axis, controller model, robot model, and software version from the alarm history screen.
- Lock out and tag out the controller and any connected pneumatic or hydraulic supply before opening the battery box or accessing the arm.
- Inspect the battery box at the robot base, confirm battery orientation, and check for corrosion or a swollen or leaking cell.
- Check the battery connector and cable routing for looseness, pinching, or chafing back to the axis junction.
- Measure battery voltage if possible; a reading well below the rated voltage confirms a dead or dying battery.
- If the battery and wiring check out, suspect the pulsecoder or encoder circuit and plan for further electrical testing or replacement.
- Do not disconnect the battery for extended periods without following the manual’s power-preservation steps, or you risk losing absolute position that is still intact.
Clearing The Alarm And Remastering
Replace robot Pulsecoder batteries with the controller powered ON (E-stop pressed), as FANUC directs, so the stored position is not lost during the swap. Correct the cause first — replace the battery, repair the cable, or replace the pulsecoder — before attempting any reset. A battery swap alone will not restore absolute position once it has actually been lost.
If absolute position was lost, the controller’s pulsecoder reset must be performed. Documented methods include momentarily setting the system variable $MCR.$SPC_RESET to TRUE, which the controller automatically returns to FALSE once the reset completes, or using the RES_PCA function on the MASTER/CAL screen where that option is available.
After the reset, cycle controller power. Then remaster or calibrate the affected axis before returning the robot to production — a pulsecoder reset alone does not restore accurate positioning. Verify mastering data, run the axis through its full range, and confirm no SRVO-062, SRVO-065, or SRVO-075 alarms return. Menu names and exact steps differ between R-30iA, R-30iB, R-30iB Plus, and R-J3iB controllers, so confirm the procedure against the maintenance manual for that specific controller and software version.
When Its A Hardware Failure
Treat SRVO-062 as a hardware failure, not just a battery problem, when the alarm returns immediately after a battery replacement, when battery voltage measures correctly at the connector but the alarm persists, or when SRVO-075 pulse-not-established keeps reappearing after a completed remaster attempt.
The parts most likely to fail, in order: the battery cable or connector inside the robot base or arm, showing an open circuit, broken wire, or corrosion; the pulsecoder or integrated motor encoder itself, with internal electronics failure, a damaged encoder disk, or a cracked housing letting in contamination; and less commonly the servo amplifier or its encoder feedback input.
Bench-level checks that separate a wiring problem from a component failure include continuity testing the battery cable end to end, checking connector pins for corrosion or damage, and verifying pulsecoder output independent of the battery. A motor or pulsecoder that fails these checks needs repair or replacement rather than another reset attempt, and any such change requires the applicable mastering procedure afterward.
How Robotics Integration Helps
Robotics Integration provides remote troubleshooting support for SRVO-062, SRVO-065, and SRVO-075 alarms on FANUC R-30iA, R-30iB, R-30iB Plus, and R-J3iB controllers, working from your alarm history and axis details to narrow down whether the fault is a battery, cable, or pulsecoder issue before parts are ordered or a truck rolls.
When a motor or pulsecoder needs to come out of the robot, we repair and test these components at the component level, including battery input, connector integrity, encoder feedback, and mechanical condition, with load testing and burn-in used to catch intermittent faults before the unit goes back into service.
On-site service is available for battery replacement, cable repair, pulsecoder or motor replacement, pulsecoder reset, and remastering on affected axes. We work with obsolete R-J3iB and older R-30iA hardware where new OEM parts may be limited, matching any repaired or exchanged assembly to your specific motor, amplifier, and controller configuration.
Looking up a different code? See the full FANUC and robot alarm code list, or read about our FANUC robot repair.
Get Help With Your BZAL Alarm
Before you call, pull together the controller model (R-30iA, R-30iB, R-30iB Plus, or R-J3iB), the exact alarm text including group and axis numbers, the full alarm history if the fault has occurred before, the robot model, and what the robot was doing when the alarm tripped — running production, homing, or coming out of a power-up.
That information lets us tell you quickly whether you are looking at a battery, a cable, or a pulsecoder problem, and what to check first. Call Robotics Integration at 1-602-449-1556 to talk through an SRVO-062, SRVO-065, or SRVO-075 alarm with a technician and get the robot moving toward a correct reset and remastering.
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