Fanuc spindle alarm C3 means that in spindle switching, a mismatch was found between the switching request signal (SPSL) and the internal status of the motor/spindle sensor signal switching circuit — the submodule SW (SSW). On machines where one amplifier serves two spindles (or switches between sensor sets), the SSW is the electronic switch that routes the sensor signals; C3 says the control asked it to switch and its internal state disagrees.
Fanuc's verdict
The manual is unusually decisive: the submodule SW (SSW) is defective — replace the SSW. The electronic switching circuit inside the module has failed; there is no adjustment.
Practical notes before ordering
- Distinguish it from its power-side cousins: AL-15/AL-55 concern the POWER lead switching (external magnetic contactors, MCFN feedback); C3 concerns the SENSOR signal switching inside the SSW module. Contactor checks will not help a C3.
- Reseat the SSW's connectors (power off, locked out) — interface cables to the amplifier and both sensor inputs; a disturbed connector after maintenance can mimic an internal fault.
- Replace with the exact-spec SSW; on machines down, exchange modules are the fast path. A repaired/replaced SSW should be verified through several switch cycles between both spindles/sensor sets before production.
Tip: C3 lives only on switching configurations — if your single-spindle machine shows something like it, re-read the display: on multi-code 7-segment displays, C-family codes are easily misread. Photograph the display and the alarm history before resetting.
Related guides
- Fanuc spindle alarm 15 (power lead switching sequence)
- Fanuc spindle alarm 55 (switching mismatch during activation)
- Fanuc spindle alarm 89 (submodule SM abnormal)
C3 on your two-spindle machine? JJ Automation supplies and repairs SSW switching submodules and verifies switching configurations on site in NCR. WhatsApp us or call +91 88022 12394.