FANUC Spindle Amplifier Alarm Codes Full List: SPM/PSM Two-Digit LED 01–88 (A/b0/C0 Letter Codes) + Replace-vs-Wire Decision

You are standing at the cabinet reading the two digits on the spindle amp’s LED. Two mistakes waste the most time: treating “SP9012 on the CNC” and “12 on the amplifier” as two different faults, and swapping a good power module because of a bad code list. This page is sorted by the two digits actually shown on the SPM display, with plain-English meaning, first action, and the decisive check for each.

1. Know the cast: SPM / PSM / SVM / spindle motor

In a FANUC serial spindle (α / αi series) the cabinet holds several power modules side by side. Which one is lit, and with what, matters:

• PSM (Power Supply Module): rectifies 3-phase 200 V into the DC link (~300 V) and regulates it, and feeds 24 V control power to the whole stack. Its own LED shows power-side codes like 01/02/04/05/07.
• SPM (Spindle Module): hangs on the DC link and drives the spindle motor. Almost all the two-digit codes in this article appear on this SPM STATUS window.
• SVM (Servo Module): also on the DC link, but drives the feed axes (X/Y/Z). It raises Sv alarms (e.g. SV0301), not the SPM codes here—don’t mix them.
• Spindle motor itself: carries the thermostat and encoder (MZi/BZi/CZi or magnetic sensor). It shows nothing, yet “motor overheat 01” and “coder disconnect 27” usually originate there.

There is also a confusingly named SPMC (αC-series built-in spindle amp): it reuses the same numeric codes as SPM, but a few (e.g. 12, 35) mean something else. Those are flagged “SPMC” in the table.

2. How to read the display: numeric codes + letter codes (A / A0–A4 / b0 / C0–C2)

The SPM front has a two-digit 7-segment LED (STATUS window). Standing by it shows 0; on alarm it shows the code and the ALM red LED lights. Three families:

1. Pure numeric 01–59: common to all standard α/αi units. This is the main table in section 3.
2. Numeric 69–88: only on αi SP units equipped with the Safety Function (safety speed monitoring, safety parameters). Machines without the safety option never show this range.
3. Letter codes: not numbers—control/communication faults—

– A / A0: SPM control program not running; A1/A2: control program processing error; A3: control-board clock error; A4: SRAM parity error.

– b0: communication error between modules (SPM–PSM)—check the cable between the two blocks first, then suspect a module.

– C0/C1/C2: serial communication data error between CNC and spindle module (fiber JA7A/JA7B or the CNC-side board).

Reading tip: the code is raised by the SPM itself and is the same fault shown on the CNC as “SP90xx” (see section 5). A letter code usually means don’t touch the power terminals yet—it is a control board / fiber / 24 V matter.

3. Alarm code full list (sorted by the two digits on the display)

The “Triage” column maps to the three paths in section 4: Replace (module/PSM body—still alarms with cable off, or control-board fault) / Wire (cable, connector, motor, incoming) / Param (init & polarity) / Mech (load, fan, regen). “SPMC” marks αC-series only.

Code	English	Meaning	First action (triage)	Decisive check / common cause
01	Motor overheat	Spindle motor overheat	Mech · fan	Motor thermostat tripped; check cooling fan, mechanical bind, sustained overload
02	Excess speed deviation	Speed deviation too large	Wire · param	Actual speed can't follow command; speed sensor/cable, load, speed-detect param
03	DC link fuse blown	DC link fuse blown	Replace	Severe overcurrent (often blown IGBT); SPM internal fuse, usually module swap
04	Input fuse / phase loss	Input fuse / phase loss	Wire (PSM side)	PSM 3-phase 200 V incoming phase loss; check incoming terminals & CX
05	Control P.S. fuse blown	Control P.S. fuse blown	Wire	AF2/AF3 control-power fuse blown
06	Overspeed (analog) / temp sensor	Overspeed (analog) or temp sensor	Wire	Analog spindle; motor temp sensor or cable open
07	Overspeed (digital)	Overspeed (>115% max)	Param · wire	Speed-detect param wrong, power-cable phase reversed, amp fault
08	+24 V overvoltage	+24 V input overvoltage	Wire	Input voltage high; check 24 V supply
09	Heat sink overheat	Heat sink overheat	Mech · fan	Amp cooling fan, cabinet airflow blocked
10	Low input voltage	Low input voltage	Wire	Incoming voltage sag; check wiring & supply
11	DC link overvoltage	DC link overvoltage	Wire (PSM side)	Regen energy during rapid decel; check PSM / regen resistor
12	DC link overcurrent	DC link overcurrent	Replace · wire	CRITICAL: motor/power-cable short, IGBT/IPM blown; trips on command = this
13	CPU memory fault	CPU memory fault	Replace	Control-board fault, swap SPM control PCB
14	ROM alarm	ROM alarm	Replace	ROM abnormal
15	Spindle switch seq.	Spindle switch / orient seq.	Param	Magnetic-pole sensor or orient param, MCC timing
16	RAM fault	RAM fault	Replace	NVRAM/RAM fault, swap control board
17	NVRAM fault	NVRAM fault	Replace	Swap control board
18	ROM checksum	ROM checksum	Replace	Program ROM checksum, swap control board
19	IU offset	U-phase current-detect offset	Replace	Usually SPM control-board fault (on at power-up)
20	IV offset	V-phase current-detect offset	Replace	Same, V phase
21	VCMD offset / sensor polarity	Position sensor polarity wrong	Param	After swap, param #4000.0 / #4001.4 polarity reversed
22	TSA offset	TSA offset	Replace	Control-board fault
23	ER offset	ER offset	Replace	Control-board fault
24	Serial data error	Serial data error	Wire	Normal if CNC is off; if it stays, check JA41/JA7A/7A7B fiber & SPM control board
25	Serial transfer stopped	Serial transfer stopped	Wire	Same, link broken
26	Cs speed sensor err	Cs contour speed sensor err	Wire	Cs contour speed sensor / cable
27	Position coder disconnect	Position / encoder signal open	Wire	Check JYA4/JYA3 encoder cable, encoder itself
28	Cs pos sensor disconnect	Cs contour pos sensor open	Wire	Cs contour position sensor / cable
29	Continuous overload	Continuous / short-time overload	Mech	Sustained overload (≈30 s / 9 V load meter); check cut & clamp
30	Input circuit overcurrent	Input-side overcurrent	Wire (PSM side)	PSM / incoming / AC reactor overcurrent; differs from 12—see section 4
31	Motor lock / V-sig lost	Motor won't turn / V-sig lost	Wire · mech	Mechanical jam, broken belt, bad speed sensor
32	Serial LSI RAM fault	Serial LSI RAM fault	Replace	Control-board fault
33	DC link precharge fail	DC link precharge fail / undervolt	Wire (PSM side)	PSM charge timeout, incoming phase loss, DC-link issue
34	Parameter out of range	Parameter out of range	Param	Spindle param wrong; not initialized after swap
35	Gear ratio out of range	Gear ratio out of range	Param	Orient magnetic-sensor param; SPMC meaning differs
36	Error counter overflow	Error counter overflow	Param	Gear ratio / position-gain param too large
37	Decel fail after EMG	No decel after EMG	Param	Motor accelerates after EMG; speed-feedback pulse param wrong
39	Cs 1-rot pos err	Cs 1-rot signal pos err	Wire · param	Cs contour detector param / cable
40	Cs 1-rot missing	Cs 1-rot signal missing	Wire	Same, signal not generated
41	Pos coder 1-rot pos err	Pos coder 1-rot pos err	Wire · param	Pos-coder pulse-count param wrong
42	Pos coder 1-rot missing	Pos coder 1-rot missing	Wire	Same, signal not generated
43	Diff-spindle coder disconnect	Diff-speed spindle coder open	Wire	Master-spindle coder open in differential-speed mode
44	A/D converter error	A/D converter error	Replace	Control-board A/D fault
46	Thread 1-rot fail	Thread 1-rot signal fail	Wire	Encoder sync signal abnormal during threading
47	Pos coder pulse abnormal	Pos coder pulse count abnormal	Wire · param	MZ/BZ pulse count abnormal, param wrong
49	Diff speed overspeed	Diff-speed overspeed	Param	Master/slave spindle sync speed diff too large
50	Sync calc overflow	Sync calc overflow	Param	Sync param wrong
51	DC link undervoltage	DC link undervoltage	Wire (PSM side)	Low-voltage form of 33 logic
52	ITP signal stopped 1	CNC sync ITP stopped 1	Wire	Inter-module sync fiber
53	ITP signal stopped 2	CNC sync ITP stopped 2	Wire	Same
54	Long-duration overcurrent	Long-duration overcurrent	Mech · wire	Fast accel or short; check load & cable
55	Switch signal mismatch	Spindle switch signal mismatch	Param	Hi/lo winding switch contactor / signal mismatch
56	Ctrl fan stopped	Control fan stopped	Mech	Amp internal fan stopped
57	PSM regen overtemp	PSM regen resistor overtemp	Wire (PSM side)	PSM regen resistor overtemp
58	PSM main fan overtemp	PSM main fan overtemp	Wire (PSM side)	PSM main-circuit fan overtemp
59	PSM internal fan stopped	PSM internal fan stopped	Wire (PSM side)	PSM internal cooling fan stopped (same number, different module than SPM 59)
69	Safety speed exceeded	Safety speed exceeded	Param	αi SP with Safety only: safety speed monitor tripped
70	Abnormal axis data	Abnormal axis data	Param	Safety axis-data abnormal
71	Abnormal safety param	Abnormal safety param	Param	Safety param wrong
72	Motor speed mismatch	Motor speed mismatch	Wire · param	Motor speed inconsistent under safety monitor
73	Motor sensor disconnect	Motor sensor disconnect	Wire	Safety encoder / motor sensor open
74	CPU test alarm	CPU test alarm	Replace	Control-board CPU self-test
75	CRC test alarm	CRC test alarm	Replace	Control-board CRC self-test
76	Safety func not executed	Safety func not executed	Param	Safety function not commissioned
77	Axis number mismatch	Axis number mismatch	Param	Safety config axis number wrong
78	Safety param mismatch	Safety param mismatch	Param	Safety params disagree on cross-check
79	Abnormal initial test	Abnormal initial test	Param	Safety initial test abnormal
81	Motor sensor 1-rot err	Motor sensor 1-rot err	Wire	Safety motor sensor 1-rot signal
82	Motor sensor 1-rot missing	Motor sensor 1-rot missing	Wire	Same, not detected
83	Motor sensor signal err	Motor sensor signal err	Wire	Safety motor sensor signal
84	Spindle sensor disconnect	Spindle sensor disconnect	Wire	Safety spindle sensor open
85	Spindle sensor 1-rot err	Spindle sensor 1-rot err	Wire	Safety spindle sensor 1-rot signal
86	Spindle sensor 1-rot missing	Spindle sensor 1-rot missing	Wire	Same, not detected
87	Spindle sensor signal err	Spindle sensor signal err	Wire	Safety spindle sensor signal
88	Radiator fan stopped	Radiator fan stopped	Mech	Radiator fan stopped
A / A0	Control prog not running	SPM control program not running	Replace	Control board / program not up
A1 / A2	Control prog error	Control program error	Replace	Control-board fault
A3	Clock error	Clock error	Replace	Control PCB clock
A4	SRAM parity	SRAM parity	Replace	Control-board SRAM
b0	Module comm error	Module comm error (SPM–PSM)	Wire · replace	Check cable between blocks first, then SPM/PSM control board
C0/C1/C2	CNC–SPM serial err	CNC–SPM serial data err	Wire	Fiber JA7A/JA7B or CNC-side serial spindle board

Note: letter codes A/b0/C0 are not in the same window logic as the numbers but all light the ALM red LED. See b0 → check the inter-module cable first; see C0–C2 → check the CNC–SPM fiber first. Don’t start by swapping a power module.

4. Triage: replace the module / chase the wire / fix the parameter

The most valuable field judgment is separating “the amp is bad” from “cable / motor / parameter” so you don’t swap an expensive board by mistake. The table groups the high-frequency codes by first action, with the one-shot decisive check.

Alarm	First action	Decisive check (how to confirm)
03 / 12 (when IGBT blown) / 13 / 16 / 18 / 19 / 20 / 32 / 44 / A0–A4	Replace	Still alarms immediately with motor U/V/W disconnected at the amp → power stage or control board shorted, it's the amp; A class and 19/20 at power-up are basically control board
04 / 05 / 24 / 25 / 27 / 30 / 31 / 33 / 43 / b0 / C0–C2	Wire	Fault follows cable/connector/motor: alarm clears when cable removed → downstream (cable or motor); 24 clears after re-seating/replacing fiber → comm link; incoming phase loss 04/33 → PSM incoming
07 / 15 / 21 / 34 / 35 / 36 / 37 / 49 / 50	Param	Not initialized after swap, polarity #4000.0/#4001.4 reversed, speed/gear-ratio param wrong; fixing param clears it
01 / 02 / 09 / 11 / 29 / 54 / 56 / 88	Mech / load / fan	Motor overheat → fan & cut; overvoltage 11 → regen; overload 29 → clamp & load meter; fan stop 56/88 → airflow
11 / 30 / 33 / 51 / 57 / 58 / 59	Check PSM (power module)	These often appear with a PSM-side alarm (e.g. SPM 30 with PSM 1, SPM 33 with PSM 5); fix the power module first

12 vs 30 (the frequent mix-up): 12 is DC-link overcurrent—trips the instant you command the spindle, usually motor/power-cable short or IGBT/IPM blown. 30 is AC input-side overcurrent—tied to PSM, incoming reactor, 3-phase incoming, often with a PSM-side alarm. Use the “cable-off” method (section 6) to locate before swapping.

5. SP vs SPM on the CNC: SP9012 and SPM 12 are the same fault, not two

The biggest field confusion: “SP9012” on the CNC screen and “12” on the spindle amp LED are the same fault shown in two places—not two alarms.

• On a serial spindle the CNC maps the amp alarm to the SP90xx family: SP9001 = amp 01 motor overheat, SP9012 = amp 12 DC-link overcurrent, SP9027 = amp 27 coder open … the last two digits are exactly the SPM LED code.
• So when the CNC shows SP9012, the SPM LED will also read 12, and the object to fix is identical. Don’t clear the SP alarm on one side while “repairing” the amp on the other—double-handling tends to widen the fault.
• The genuinely different family is the old analog spindle 7xx alarms (e.g. 749/754): those are at the CNC’s analog interface level, with no SPM LED to match, and are handled differently (analog speed command / tachogenerator).

广告

Memory rule: serial spindle SP90xx = amp LED xx; analog spindle 7xx = a different beast.

6. Service notes: protect the person first, then the machine

1. Lock out and wait ≥ 5 minutes: the SPM/PSM DC link holds ~300 V; the charge LED (CHARGE) must be off before it’s safe. Touching U/V/W or the bus bar before discharge risks shock and module blow-up.
2. Never unplug the encoder (JYA4/JYA3) live: coder-open 27 often follows a hot-plug, and live plugging also kills the encoder and SPM interface. Power down and discharge first.
3. Always re-initialize spindle parameters after a swap: after replacing the SPM or spindle motor, re-check the motor model code (e.g. 4133), auto-set params, and sensor polarity #4000.0/#4001.4—polarity alarm 21 is almost always this step skipped.
4. Use the “cable-off” method to locate, then decide to swap: disconnect the motor U/V/W at the amp and command low speed—still trips 12 immediately → amp power stage shorted; no trip → problem is downstream cable or motor. Megger the cable/motor at 500 V DC; phase-to-ground below ~1 MΩ is your fault.
5. Count the bus-bar screws before swapping: missing screws on the SPM/PSM bus bars cause poor contact and in turn raise 30. Seat every screw on both blocks when reinstalling (a point repair shops repeat).

Frequently Asked Questions

What is the difference between a FANUC spindle amplifier alarm and a CNC alarm?

The spindle amplifier (SPM) raises 01–88 numeric codes or A/b0/C0 letter codes on its own LED; the CNC maps those to SP90xx (serial spindle) or shows analog-spindle 7xx alarms. They are the same fault viewed from two places—on a serial spindle, SP9012 is simply amp code 12. The difference is only “where you look,” not “whether it’s one fault.”

Does SPM showing 24 mean the amplifier is bad?

Not necessarily, and usually not the amp body. 24 is a serial communication data error between CNC and spindle module: if it shows because the CNC is powered off while the SPM is up, that’s normal and clears when the CNC comes on. If it persists after power-up, re-seat or replace the JA41/JA7A/JA7B fiber and connectors first; only then suspect the SPM control board. Don’t swap the power module up front.

How do I tell FANUC spindle amplifier alarm 12 and 30 apart?

12 = DC-link overcurrent, fault in the SPM power stage, spindle motor, or power cable (trips on command, usually short / IGBT blown). 30 = AC input-side overcurrent, fault in the PSM, incoming reactor, or 3-phase incoming, often with a PSM-side alarm at the same time. In the field use the “cable-off” method: still trips with motor U/V/W off → amp; no trip → downstream cable/motor; if a PSM alarm accompanies it, check the power module first.

Last updated: 2026-10-25