On older FANUC controls (Series 0, 15, 16, 18, 21), the PMC program is stored in SRAM backed by a battery. If the battery voltage drops below 2.7V, the memory begins to fragment or lose bits. When the machine is powered off and on, the missing data triggers a checksum error, resulting in alarm 7115.
: The most common culprit is a failing power supply module, often an Izumi or similar 24VDC unit . Even if a multimeter reads 24V, the unit may be dropping voltage under the load of shifting gears or tool changes. fanuc 7115 alarm
The spindle speed switching contactors are not pulling in correctly during power-on or mode switching. 24VDC Power Supply Failure: On older FANUC controls (Series 0, 15, 16,