What causes fault code AB-F007 (PLC Redundancy Switchover)?

Primary processor encountered unrecoverable fault. Redundancy chassis link cable disconnected. Primary power supply failed. Manual switchover initiated by operator. Primary processor firmware crash

How do I fix fault code AB-F007?

Check which processor is now primary in Controller Properties. Inspect original primary for fault codes — resolve root cause. Verify redundancy link cable is secure between chassis. Check power supply status on both chassis. If switchover was unexpected, investigate and fix before clearing alarm

PLC Redundancy Switchover

AB-F007

ControlLogix redundancy pair performed a switchover. Secondary processor took over from primary.

critical allen-bradley

allen-bradley redundancy switchover controllogix

Probable Causes (ranked)

Primary processor encountered unrecoverable fault
Redundancy chassis link cable disconnected
Primary power supply failed
Manual switchover initiated by operator
Primary processor firmware crash

Fix Steps

1 Check which processor is now primary in Controller Properties
2 Inspect original primary for fault codes — resolve root cause
3 Verify redundancy link cable is secure between chassis
4 Check power supply status on both chassis
5 If switchover was unexpected, investigate and fix before clearing alarm

Field Trick

The blue LINK LED on both 1756-RM2 modules should be solid. If one is off, the redundancy link is broken.

Need a deeper diagnosis with photo analysis and AI-powered troubleshooting?

Run Full Diagnosis