What causes fault code AB-PF-F029 (PowerFlex VFD Fault F029 â€” Analog Input Loss)?

Analog signal wire broken or disconnected at drive terminal or PLC output. PLC analog output module faulted or channel failed â€” no output to drive. Signal wire shorted to shield or ground â€” pulling signal below 4mA. PLC program not writing to the analog output â€” logic fault or task not running. Analog output scaling mismatch â€” PLC output 0-10V but drive expecting 4-20mA

How do I fix fault code AB-PF-F029?

Measure analog signal at drive input terminal with multimeter set to mA â€” should read 4-20mA range. If signal is 0mA, check PLC analog output module â€” verify channel LED status and output value in PLC program. Trace analog wiring from PLC output to drive input â€” check for loose terminals, broken wires, or pinched cable. Verify PLC program is actively writing to the analog output â€” check ladder logic or function block. Confirm signal type matches â€” drive parameter must match PLC output (4-20mA vs 0-10V). If using 4-20mA, check that the loop power supply is functioning â€” measure voltage across the loop. As temporary workaround, configure drive for keypad speed reference to keep motor running while troubleshooting analog

PowerFlex VFD Fault F029 â€” Analog Input Loss

AB-PF-F029

PowerFlex drive lost the analog input signal used for speed reference. Signal dropped below the configured loss threshold (typically below 4mA on a 4-20mA loop).

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allen-bradley powerflex vfd drive F029 analog input 4-20mA signal loss speed reference

Probable Causes (ranked)

Analog signal wire broken or disconnected at drive terminal or PLC output
PLC analog output module faulted or channel failed â€” no output to drive
Signal wire shorted to shield or ground â€” pulling signal below 4mA
PLC program not writing to the analog output â€” logic fault or task not running
Analog output scaling mismatch â€” PLC output 0-10V but drive expecting 4-20mA

Fix Steps

1 Measure analog signal at drive input terminal with multimeter set to mA â€” should read 4-20mA range
2 If signal is 0mA, check PLC analog output module â€” verify channel LED status and output value in PLC program
3 Trace analog wiring from PLC output to drive input â€” check for loose terminals, broken wires, or pinched cable
4 Verify PLC program is actively writing to the analog output â€” check ladder logic or function block
5 Confirm signal type matches â€” drive parameter must match PLC output (4-20mA vs 0-10V)
6 If using 4-20mA, check that the loop power supply is functioning â€” measure voltage across the loop
7 As temporary workaround, configure drive for keypad speed reference to keep motor running while troubleshooting analog

Field Trick

Set the drive to LOCAL/KEYPAD speed reference temporarily (front panel). This takes the analog input out of the loop and lets you run the motor at a fixed speed while you troubleshoot the analog signal path.

Suggested Replacement Parts

Parts matched to fault category: Vfd Drive

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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