What causes fault code AB-PF525-F2 (PowerFlex 525 Fault F002 — Auxiliary Input)?

External device genuinely tripped — motor thermistor, bearing RTD, pressure switch, etc.. Digital input wiring disconnected — if configured as NC (normally closed), open wire = fault. External device failed — contact stuck open or closed. Wrong digital input function assignment — input configured as Aux Fault when it should be something else. 24VDC supply to external device circuit lost

How do I fix fault code AB-PF525-F2?

Identify which digital input is configured as Aux Fault — check P033 [Digital In1 Sel] through P038. Trace wiring from that digital input terminal back to the external device. Check external device status — is the thermal switch tripped, pressure switch open, etc.. Measure voltage at the digital input terminal — 24VDC present or absent tells you the circuit state. If external device is healthy, check wiring continuity end-to-end. If you need to bypass temporarily for troubleshooting, change the digital input function to 'Not Used' — but restore before production

PowerFlex 525 Fault F002 — Auxiliary Input

AB-PF525-F2

PowerFlex 525 external fault input is active. Digital input configured as 'Auxiliary Fault' is seeing an active signal from an external device (thermistor, pressure switch, flow switch, etc.).

medium allen-bradley vfd

allen-bradley powerflex 525 auxiliary digital input external fault

Probable Causes (ranked)

External device genuinely tripped — motor thermistor, bearing RTD, pressure switch, etc.
Digital input wiring disconnected — if configured as NC (normally closed), open wire = fault
External device failed — contact stuck open or closed
Wrong digital input function assignment — input configured as Aux Fault when it should be something else
24VDC supply to external device circuit lost

Fix Steps

1 Identify which digital input is configured as Aux Fault — check P033 [Digital In1 Sel] through P038
2 Trace wiring from that digital input terminal back to the external device
3 Check external device status — is the thermal switch tripped, pressure switch open, etc.
4 Measure voltage at the digital input terminal — 24VDC present or absent tells you the circuit state
5 If external device is healthy, check wiring continuity end-to-end
6 If you need to bypass temporarily for troubleshooting, change the digital input function to 'Not Used' — but restore before production

Field Trick

On a PowerFlex 525, the Aux Fault input is often wired to a motor thermistor relay. If the motor is cool and the fault is active, check the thermistor relay itself — the relay contact may have failed. Bypass the relay temporarily (not the thermistor) to confirm.

Suggested Replacement Parts

Parts matched to fault category: Vfd

Allen-Bradley PowerFlex 525 AC Drive 1HP P/N: 25B-D2P3N114 1HP, 480V, 3-phase, built-in EtherNet/IP, EMC filter

AutomationDirect $395.00 Amazon $450.00 Grainger $520.00

ABB ACS580 General Purpose Drive 2HP P/N: ACS580-01-05A7-4 2HP, 480V, built-in safe torque off, adaptive programming

AutomationDirect $425.00 Amazon $480.00 Grainger $550.00

GS20 AC Drive 1HP (Budget Option) P/N: GS20-20P5 1HP, 230V, sensorless vector, compact size — good replacement for testing

AutomationDirect $149.00 Amazon $175.00

Prices are estimates. Verify part numbers match your equipment before ordering.

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