External Fault (Simultaneous Fwd/Rev Command)

What does EF mean?

Both the forward and reverse run commands were input simultaneously for 500ms or more, causing the motor to stop. This is an external sequencing logic error, which could lead to motor damage or unsafe operation if not corrected.

• Faulty or miswired external control relay logic providing simultaneous forward and reverse signals to the drive.
• PLC or controller programming error sending conflicting run commands to the drive's digital inputs (e.g., S1 and S2).
• Stuck pushbuttons or selector switches on the operator panel maintaining both FWD and REV command signals.
• Internal short or external wiring fault causing both digital input terminals (e.g., S1 for FWD, S2 for REV) to be active.

Click steps to track your progress.

1. 1

   1. Inspect wiring to digital input terminals (e.g., S1 and S2) for accidental shorts or cross-connections.

2. 2

   2. Using a multimeter, verify that only one run command signal (e.g., 24VDC to S1 or S2) is active at any time.

3. 3

   3. Review the PLC or controller program logic responsible for forward/reverse commands, ensuring interlock conditions are met.

4. 4

   4. Test external control devices (e.g., relays, selector switches) for proper operation and contact integrity.

5. 5

   5. Temporarily disconnect one of the potentially conflicting run command wires (e.g., from S2) to see if the fault clears.