Sometimes, after a controlled shutdown or a battery replacement, the system performs a memory check which can take longer than usual. Wait at least 5 minutes to ensure it isn't just a slow boot.
Using a multimeter, measure the voltage on the FANUC battery pack (located on the front of the main CPU board or in a separate battery cassette). A new battery reads 3.6V. If it reads below 3.0V, replace it while the control is powered on to avoid losing SRAM. After replacement, power cycle. If the frozen boot persists, you may have already suffered SRAM corruption from low voltage.
| Scenario | Recovery Method | |----------|----------------| | Dead battery, lost parameters | Reload from paper tape or PC backup using IPL → SRAM download. | | Corrupted ladder (PMC) | Reload PMC from memory card via boot loader (Function 1: Load from memory card). | | Corrupted system software | Reload entire FANUC system software using FANUC BOOT CD or memory card (requires FANUC factory tools). | | Hardware failure | Replace main board (A20B series) or send to FANUC repair center. | fanuc starting system software please wait
Physical hardware failure is less common but does occur. Electrolytic capacitors on older FANUC 16/18/21 series main boards (circa 1995–2005) degrade over time, causing unstable voltage rails. Also, the "Master PCB" or "Main CPU Board" (e.g., A16B-3200-xxxx) can develop cracked solder joints on the DRAM chips.
Why does the system get stuck on "PLEASE WAIT"? There is rarely a single cause. Based on field data and FANUC service bulletins, the following are the most frequent culprits. Sometimes, after a controlled shutdown or a battery
Contact professional service if:
Use compressed air and a ESD-safe brush. Dust buildup increases operating temperature, accelerating flash memory degradation. Pay special attention to the FROM and SRAM modules—they run hot. Physical hardware failure is less common but does occur
When a FANUC CNC displays "Starting system software please wait" (or similar), the controller is initializing firmware, loading system software modules, or performing a firmware/self-check after power-on or a reboot. It can be normal for several seconds to a few minutes, but extended or repeated hangs indicate a problem.