Troubleshooting Red LED Beep on SINAMICS S120 6SL3320-1TE32-1AA3

Problem Overview

The Siemens SINAMICS S120 Single Motor Module 6SL3320-1TE32-1AA3 is a chassis-format, internal air-cooled inverter module rated for 600 V DC link input and 3-phase 400 V, 210 A output. When the module powers up and a red status LED illuminates on the front panel — often combined with an intermittent audible beep from the integrated pre-charging contactor or an external 24 V signal horn — operators must treat it as a fault-state indicator until proven otherwise through engineering diagnostics.

The two symptoms reported together (red LED + intermittent "bip bip") on the 6SL3320-1TE32-1AA3 fall into one of three categories:

1. Active drive fault (F-code present in the SINAMICS alarm buffer)
2. Alarm-only condition (A-code pending acknowledgement, but not yet latched as fault)
3. Hardware-level fault (over-temperature, fan failure, DC-link undervoltage, pre-charge contactor cycle retry, or EP-terminal wiring fault)

This reference walks through every layer of diagnostic escalation, from the front-panel LEDs of the Motor Module through SIMOTION / STARTER / Startdrive online diagnostics, and finally to the mechanical inspection of the integrated pre-charging relay.

Hardware Identification and Ratings

The MLFB 6SL3320-1TE32-1AA3 decodes as follows (per Siemens catalog data and the official product data sheet):

Official product data is published on the Siemens Industry Mall at 6SL3320-1TE32-1AA3 — Industry Mall and on the data sheet service at 6SL3320-1TE32-1AA3 PDF data sheet. Cross-reference the printed barcode on the nameplate against these pages if the MLFB appears ambiguous (for example, when comparing to the variant 6SL3320-1TE32-1AC3, which differs in internal firmware version and control interface).

Front-Panel LED Meanings on the Motor Module

The 6SL3320-1TE32-1AA3 chassis Motor Module exposes a small status-LED bar on the front of the unit. Each LED maps to one of the conditions defined in the SINAMICS S120 List Manual (LH1) and the operating instructions for chassis components:

If the red LED appears on the RDY indicator, the Motor Module has latched at least one F-code. If the red LED appears on the OPT indicator, the fault is at the DRIVE-CLiQ or component-recognition layer (cable, neighbor, or Control Unit missing).

Interpreting the Audible "Bip Bip"

The SINAMICS S120 chassis Motor Module does not contain a self-resonant piezo buzzer inside the 6SL3320-1TE32-1AA3 itself. The intermittent "bip bip" tone heard during operation is therefore one of the following:

1. Pre-charging contactor cycling: The internal pre-charge relay (line-side DC-link charging circuit) cycles open/close when the DC-link voltage fails to reach its enable threshold within a configurable window (typically 3 s). Each cycle produces a sharp mechanical click that can sound like "bip"; two cycles in succession = "bip bip."
2. External 24 V horn: Many cabinets wire a 24 V DC signaling horn or strobe to the EP terminals (Enable Pulses) of the Motor Module. When the drive drops to OFF2 / OFF3 or pulses are inhibited, the horn driver pulses intermittently if the wiring is configured for latched alarms with pulse-pattern acknowledgement.
3. Fan / blower contactor: Internal cooling fan failure triggers F30004 (heat-sink overtemperature pre-warning) or A30004 followed by F30005; the cooling-fan relay may chatter if supply is intermittent.
4. External PLC annunciator: A separately programmed SIMATIC S7 / SIMOTION annunciator horn tied to the drive's fault word.

To isolate the source, place one hand on the front-panel of the Motor Module and feel for the click at the instant of each "bip." A click felt at the pre-charge relay area (lower-front right of chassis FX) confirms case 1. A click at the cooling fan shroud confirms case 3. No internal click — only an external cabinet sound — confirms case 2 or 4.

Step-by-Step Diagnostic Procedure

Follow the escalation ladder in order. Each step gates the next.

Step 1 — Online connection via SIMOTION / STARTER / Startdrive

1. Open SIMOTION SCOUT (≥ V4.5) or TIA Portal with Startdrive (≥ V15.1) on the engineering station.
2. Navigate to the SINAMICS Integrated / CX32 / CU320-2 to which the 6SL3320-1TE32-1AA3 is connected via DRIVE-CLiQ.
3. Open the project, go online, and select the affected drive object (DO) — typically the second or third DO after the line module.
4. Open the Diagnostics → Alarms view. The buffer stores both active and historical F-codes with timestamp and fault value (r2125).
5. If a fault is reported, record the F-code, the fault value (r0949), and the supplementary information (r0950 / r0951 / r0952).
6. If the buffer is empty but the red LED persists, check the Alarms (A-code) buffer separately.

The fact that the SIMOTION online view showed "no alarm" in the field report does not exclude an F-code; it typically means the diagnostic view was filtered to the SIMOTION runtime alarms, not the SINAMICS drive-object alarms. Re-check the drive-level (not SIMOTION-level) fault buffer.

Step 2 — Read the fault buffer directly via BOP20 / AOP30

1. Connect the Basic Operator Panel (BOP20) or Advanced Operator Panel (AOP30) to the front X-interface of the Motor Module.
2. Navigate to menu r0000 → r0010 → r0050 → r0947[0..7].
3. r0947[0] = most recent active fault; r0947[1..7] = fault history.
4. For each F-code, read r0949[0..7] = fault value and r0950[0..7] = supplementary fault value 1.

Step 3 — Verify the DRIVE-CLiQ topology

1. In STARTER / Startdrive, open Topology view.
2. Confirm the 6SL3320-1TE32-1AA3 appears with the correct firmware version reported.
3. Compare component numbers (MLFB) against the as-installed hardware; a mismatch causes F0135 / F0136.

Step 4 — DC-link and pre-charge inspection

1. With the drive offline and the line contactor confirmed open, measure the DC-link voltage between DC+ and DC- test points.
2. A residual voltage > 50 V after 5 minutes indicates a stuck pre-charge contactor — investigate the EP wiring and the line-side infeed.
3. Re-energize the line and time the pre-charge (parameter p0857 = pre-charging time monitor, default 3000 ms).

Step 5 — EP terminal and 24 V supervision

1. Measure +24 V at the EP (Enable Pulses) terminal block X9. Pin 1 = +24 V, Pin 2 = M (0 V), Pin 3 = shield.
2. Loss of EP +24 V latches F7492 (signal "OFF2" missing) or F7483 (signal "OFF3" missing) depending on configuration.

Step 6 — Cooling fan and heat-sink

1. With the Motor Module powered, verify the internal fan is running (audible, or feel airflow at the exhaust grille).
2. Read r0037[0] = Motor Module temperature. If > 90 °C, check for blocked filters / ambient > 40 °C.
3. F30004 (heat-sink overtemperature) and F30005 (chip overtemperature) are the typical thermal F-codes.

Common F-Codes Affecting the 6SL3320-1TE32-1AA3

Root-Cause Matrix for Red LED + Beeping on Chassis Motor Modules

Verification After Repair

Once the root cause is cleared, complete this verification checklist before returning the drive to production:

1. Acknowledge all active faults (using the AOP30, BOP20, or p3981 = 1 on the drive).
2. Confirm RDY LED is solid green and DC-LINK LED is on.
3. Run the Motor Module through commissioning test p0010 = 1 → p0010 = 0 with motor disconnected (motor identification disabled).
4. Apply OFF1 enable, then release; verify no F-code is latched.
5. Record the firmware version (r0018) and project version, and archive the project.
6. Re-measure the DC-link with a CAT IV meter to confirm pre-charge completes within 3 s.
7. Listen for any chatter from the pre-charge contactor during three consecutive start cycles.

Preventive Recommendations

• Replace cabinet air filters at the documented interval (Siemens recommends every 12 months in dusty environments; more frequently if airborne contamination is high).
• Log r0037 (heat-sink temperature) and r0039 (chip temperature) to a trend so thermal drift is visible before reaching F30004.
• Inspect DRIVE-CLiQ connectors for dust and corrosion; torque to specification.
• Verify EP wiring is sourced from a dedicated 24 V channel that does not share a common return with inductive loads.
• Keep the SINAMICS firmware aligned with the version published on the Siemens Product Support page; mixed-version DRIVE-CLiQ chains cause intermittent F0135/F0136 that look like an LED fault.

FAQ