What it means
The message comes from a Terminal Module (TM) and reports that the 24 V power supply for the module's digital outputs is missing. It is raised here as alarm A35906; depending on how the drive is configured, the same condition can also be output as a fault or with no reaction at all. The drive itself takes no protective action — it only reports the missing supply voltage.
Why it appears
- The 24 V power supply for the digital outputs of the Terminal Module is missing.
What to check
- Read the alarm value in r2124 (interpret hexadecimal) to identify which Terminal Module and which DI/DO group is affected.
- Check the terminals for the power supply voltage: L1+, L2+, L3+ and M — or +24 V_1 on a TM41.
Reading the message value
The message value (%1) is the alarm value, which the drive stores in r2124; interpret it hexadecimal. Each value names the Terminal Module and the DI/DO group whose 24 V supply is missing:
- 01: TM17 24 V power supply for DI/DO 0 ... 7 missing
- 02: TM17 24 V power supply for DI/DO 8 ... 15 missing
- 04: TM15 24 V power supply for DI/DO 0 ... 7 (X520) missing
- 08: TM15 24 V power supply for DI/DO 8 ... 15 (X521) missing
- 10: TM15 24 V power supply for DI/DO 16 ... 23 (X522) missing
- 20: TM41 24 V power supply for DI/DO 0 ... 3 missing
Parameters the manual names
- r2124 — alarm value of this message; read it hexadecimal to see which Terminal Module DI/DO group has lost its 24 V supply.
Acknowledging and restarting
As an alarm, A35906 needs no acknowledgement — restoring the 24 V supply at the terminals is the fix. If the drive is configured to output the condition as a fault instead, it is acknowledged immediately, and a POWER ON also acknowledges it.
The same on every family
Every manual that describes A35906 gives it the same reaction, acknowledgement and message class.
| Drive family | Reaction | Acknowledge | Message class | Component | Manual |
|---|---|---|---|---|---|
| S120, S150 | NONE | NONE | Supply voltage fault (undervoltage) (3) | Terminal Module (TM) | SINAMICS S120, S150 List Manual · p. 3242 |
| G130, G150 | NONE | NONE | Supply voltage fault (undervoltage) (3) | Terminal Module (TM) | SINAMICS G130, G150 List Manual · p. 1904 |
The drives this code lives on
A35906 is described for G130, G150, S120, S150. These are the converters of those families in our catalogue — price on request.
Questions technicians ask
What does alarm A35906 mean on a SINAMICS drive?
A Terminal Module reports that the 24 V power supply for its digital outputs is missing. The drive takes no protective action; it only signals the missing supply.
How do I find out which terminal module is affected?
Read the alarm value in r2124 and interpret it hexadecimal. 01 and 02 point to the TM17, 04, 08 and 10 to the three TM15 terminals X520, X521 and X522, and 20 to the TM41.
Which terminals feed the 24 V supply for the digital outputs?
Check the terminals for the power supply voltage L1+, L2+, L3+ and M. On a TM41 the relevant terminal is +24 V_1.
Does A35906 have to be acknowledged?
No acknowledgement is required while the message appears as an alarm. If it is configured as a fault, it is acknowledged immediately or via POWER ON.
Codes next to this one
Source
Written from Siemens' own List Manuals and operating instructions; every number, designation and parameter on this page is checked against them before publication.
All SINAMICS codes: fault and alarm codes · the A35xxx group · SINAMICS manuals · Siemens manuals