What causes Heidenhain alarm 330-008A?

Inverter not ready. Safety relay fault. PWM bus interruption. Open guard doors.

How do I fix Heidenhain alarm 330-008A?

1. Note the full error text and the NC software number of the control. 2. Contact your machine builder or HEIDENHAIN service.

Heidenhain codes

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Heidenhain Controller

Safety · Intermediate · 30-120 minutes

Alarm 330-008A

HEIDENHAIN 330-008A - CC inverter for axis RDY=0 (safety relay)

The CC inverter module is not receiving the ready signal from the machine's safety relay circuit, preventing axis enable. This is either due to an active safety condition (E-stop, door open), a failure in the safety relay circuit itself, or an internal fault within the CC inverter that has caused the safety relay to de-energize as a protective measure.

HeidenhainSafetyIntermediate30-120 minutes

330-008A

HEIDENHAIN 330-008A - CC inverter for axis RDY=0 (safety relay)

CC inverter for axis RDY=0 (safety relay)

The power module could not be switched to ready condition. This may be due to safety relay issues, wiring faults, or defective power modules.

Root Cause Summary

Safety

Refer to Heidenhain service manual
Ensure qualified technician performs repairs

Causes and Fixes

1
Verify All E-Stop Buttons Released
Walk around the machine and visually confirm all emergency stop mushroom buttons are in the released (rotated) position. Pull and release each E-stop to verify proper mechanical operation and contact closure.
Do not bypass or jumper E-stop circuits - this violates safety standards and creates serious hazards.
2
Check Safety Door and Interlock Switches
Open and close all safety doors and guards while observing if the alarm clears. Check limit switches and magnetic safety switches for proper alignment and function. Look for damaged actuators or misaligned switch mounting.
On machines with multiple safety zones, one faulty door switch can prevent all axes from enabling - systematically check each zone.
3
Verify Safety PLC Outputs
If machine uses a safety PLC (Pilz, Sick, etc.), check the safety PLC diagnostic LEDs or connect to the safety PLC programming software to verify all monitored circuits show closed/safe status and outputs are energized.
Some machines require a specific power-up sequence - safety PLC must fully boot before energizing axis enable relays.
4
Check Main Safety Relay Contactor
Locate the main safety relay (usually K1 or similar designation in electrical cabinet). Verify the relay coil is energized and contacts have closed. Measure 24VDC across coil terminals and continuity across NO contacts.
Listen for the relay 'click' when releasing E-stop - absence of sound indicates relay coil or power supply issue.

1
Inspect CC Inverter LED Indicators
Open the control cabinet and locate the CC inverter module for the affected axis. Check the front panel LED indicators - Heidenhain CC modules typically have LEDs for RDY (green), FAULT (red), and DC BUS OK (green). Document which LEDs are on/off/blinking.
High voltage present in control cabinet - observe lockout/tagout procedures and use appropriate PPE.
2
Check CC Inverter DC Bus Voltage
Using a multimeter, measure DC bus voltage at the CC inverter DC terminals (typically labeled + and -). Should read approximately 565VDC for 400VAC supply or 282VDC for 230VAC supply. Low voltage indicates power supply or rectifier issues.
Measure DC bus voltage only with appropriate high-voltage rated meter and extreme caution - lethal voltage present.
3
Verify CC Inverter Cooling
Check that cooling fans on the CC inverter module are running and heatsink fins are not blocked by dust. Feel heatsink temperature (when powered down) - excessive heat indicates thermal issues. Clean filters and verify cabinet ambient temperature is within spec (typically <40°C).
CC inverters often have thermal sensors that will prevent RDY signal before visible thermal shutdown - check if alarm appears after extended operation.
4
Reset CC Inverter Module
Power down the complete control system using the main disconnect. Wait 60 seconds for DC bus capacitors to discharge completely. Power back up and observe if alarm clears. Some CC internal faults are latching and require full power cycle to reset.
If alarm clears after power cycle but returns during operation, indicates intermittent fault - monitor DC bus voltage and motor temperature during operation.
5
Check for Overcurrent Conditions
Access Machine Parameters and review the actual current values for the affected axis (MOD > System > Machine > Axis Currents). Compare against motor nameplate ratings. Excessive current indicates mechanical binding, motor issues, or incorrect parameter settings.
In TNC diagnostics, monitor the axis following error - excessive following error combined with high current suggests mechanical problems causing CC overload.

DIY Feasiblemedium confidence

Call a technician if:

·If no faults are found in wiring or relay after thorough testing
·If inverter configuration changes do not resolve the issue or if access to settings is restricted

Prevention

Regularly inspect and tighten wiring connections at X72 and safety relays to prevent loosening over time.
Schedule periodic maintenance checks on inverter hardware and software configurations.
Protect signal wiring from physical damage by routing away from high-vibration areas.

Common Mistakes

Overlooking intermittent wiring issues by not testing under load or movement conditions.
Attempting inverter configuration changes without referencing the specific machine manual, leading to mismatched settings.

Related Alarms

330-008B 330-009A 401-002C

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Always verify with your machine manual or a certified technician before performing service procedures.