231-E031

Decode FS Output Status

Convert the bit-encoded values %4 (outputs 0-31) and %5 (outputs 32-63) from decimal to binary to identify which specific FS outputs are stuck high.

Use Windows calculator in programmer mode or create a binary conversion chart for quick field diagnosis

Isolate Affected FS Outputs

Disconnect the external wiring from the identified FS output terminals on the CC unit. Check if alarm clears after power cycle.

Ensure machine is in safe state and follow LOTO procedures before disconnecting safety circuits

Test External Wiring

Measure resistance between the disconnected FS output wires and +24V supply using a multimeter. Resistance should be >1MΩ.

Check for moisture ingress in junction boxes and damaged cable insulation in cable chains

Verify FS Output Module

If external wiring tests good, the FS output module on the CC unit may be defective and requires replacement.

FS output module replacement requires safety system re-commissioning and validation

Check CC Unit Status LEDs

Examine the CC unit front panel LEDs for any error indications. Red safety LED or flashing patterns indicate internal safety system faults.

Document LED patterns with timestamps for Heidenhain technical support

Perform CC Unit Diagnostic Test

Access MOD function and run internal diagnostics if available. Check for additional safety-related error messages in the error log.

Do not attempt to bypass safety diagnostics or force-clear safety alarms

Verify Power Supply Quality

Measure +24V supply voltage at CC unit terminals. Voltage should be 24V ±10% with <5% ripple. Poor power quality can cause safety module malfunctions.

Use oscilloscope to check for voltage spikes or noise that may corrupt safety processor operation

Replace CC Unit

If diagnostics confirm internal failure, replace the CC unit and restore safety configuration from backup.

Safety system recertification required after CC unit replacement

Check Safety Parameter Integrity

Access safety configuration menu and verify all FS output assignments and parameters match the machine documentation.

Compare current configuration with known-good backup or commissioning documentation

Restore Safety Configuration

Load verified safety configuration from backup file or re-enter parameters according to machine safety specification.

Only qualified safety engineers should modify safety configurations

Perform Safety Validation Test

Execute complete safety system validation including all FS outputs to ensure proper operation after configuration restore.

Machine must pass full safety validation before returning to production

Check Cable Shielding

Verify that all FS output cables have proper shielding connected to ground at the CC unit end only. Check for damaged or disconnected shield connections.

Use EMI clamp-on filter as temporary test to isolate noise-related issues

Identify Noise Sources

Look for nearby high-power switching devices, VFDs, or welding equipment that may be generating EMI affecting the safety circuits.

Maintain minimum separation distances per Heidenhain installation guidelines

Implement Noise Suppression

Install ferrite cores on affected FS output cables and ensure proper grounding of all electrical enclosures and cable shields.

Route safety cables in separate conduits from power and motor cables