Allen-Bradley PowerFlex 70 (20A/20D) and PowerFlex 700 (20B/20C/20BD) drives still run fans, pumps, conveyors and extruders worldwide. Both platforms are long past end of life, and a new PowerFlex 755 replacement can take 16–24 weeks. Keeping the installed 20A and 20B units alive is far cheaper than replacing them — and reading the fault code correctly is the most valuable skill in that job.
This guide covers the codes behind most PowerFlex 70/700 service calls — F004, F005, F007, F008, F012, F013, F070 and F081 — with fault manifestations, root causes and repair steps. Replacement drives and spare modules are listed in our Allen-Bradley PowerFlex replacement drives range.
Faults latch: they do not self-clear, and must be reset from the Stop/Reset key, a digital input configured as fault reset, or a power cycle. The fault queue survives a stop, restart and reset until explicitly cleared, so capture the whole queue before clearing it — the newest code is often a symptom and an earlier entry is the root cause.
| Symptom seen on the machine | Code to look at first |
|---|---|
| Trips instantly at start, sometimes with an audible bang | F012, F013 |
| Trips at the end of a deceleration ramp | F005 |
| Trips after 15–60 minutes of running, worse on hot days | F008 |
| Trips when plant load steps up, or a large motor starts nearby | F004, F007 |
| Trips with the motor disconnected | F012, F070 |
| Drops to minimum frequency and recovers by itself | F081, F029 |
Manifestations. Trips shortly after a start command, or whenever a large load switches on elsewhere on the feeder. On a 480 V drive the DC bus fell below roughly 407 V DC.
Root causes. A supply sag; loose or corroded terminations that drop voltage under current; a blown input fuse or pitted disconnect contact; aged DC bus capacitors that sag under load and recover at rest.
Repair steps. Measure all three line phases at the drive terminals under load, not at rest. Torque the line and motor lugs and replace any showing heat discoloration. Check input fuses and confirm all three phases. If input power is stable but the bus still droops under load, measure DC bus capacitor ESR — on a drive over eight to ten years old, capacitor replacement is the fix.
Manifestations. Trips at the end of a deceleration ramp, or while a gravity or overhauling load drives the motor faster than commanded. The DC bus exceeded about 130% of nominal.
Root causes. Deceleration time too short for the load inertia; no dynamic braking resistor, or one that has failed or been left disconnected; a regenerative load such as a hoist or centrifuge.
Repair steps. Increase the deceleration time until the trip stops — this alone resolves most F005 events. Confirm the dynamic brake resistor is connected and measure its resistance, replacing it if the value has drifted or the body is cracked. A failed brake chopper turns a normal decel into an overvoltage trip, so check that circuit too.
Manifestations. Trips after several minutes of running at high load, with the motor frame hot to the touch.
Root causes. Motor nameplate FLA not matching the value programmed in the drive (most common, usually after a motor swap); mechanical binding such as a seized bearing or jammed conveyor; a failed motor cooling fan.
Repair steps. Re-enter the FLA from the nameplate and verify the overload class matches the motor design. Disconnect the load and turn the driven equipment by hand; if it is stiff, fix the mechanical side first. Do not raise the FLA to stop the trip unless the nameplate justifies it — that masks the fault and cooks the motor.
Manifestations. Trips after 15–60 minutes of running, faster on hot days; the heatsink is hot to the touch.
Root causes. Heatsink fins fouled with dust, lint or oil mist; a failed or slow cooling fan; high panel ambient temperature or a clogged cabinet filter.
Repair steps. Lock out and tag out, wait five minutes, and confirm the DC bus is below 50 V before touching anything. Clean the fins with dry compressed air — any coating insulates the metal and stops heat transfer. Test the fan: it should spin freely at full speed, and a fan with bearing noise is the front end of most F008 events. Fan assemblies are the highest-wear item on these drives, so many sites replace them at about five years. Verify cabinet airflow, replace air filters every three months, and keep heatsink temperature below about 75 °C.
Manifestations. An instantaneous trip, often at start and sometimes with an audible bang. On a badly damaged unit the drive will not reset even with the motor leads removed.
Root causes. A short in the motor cable or windings; a ground fault; a failed IGBT with loss of desaturation detection; a failed gate driver.
Repair steps. Disconnect the motor leads and attempt a reset — if the fault clears, the cable or motor is at fault. Megger the cable and windings phase-to-phase and phase-to-earth, and look for pinches, chafing, moisture or rodent damage. If F012 persists with the motor disconnected, the IGBT bridge or gate driver has failed: that is a power-stage fault needing component-level repair or replacement.
Manifestations. Trips at start or at random intervals; the sum of the three output currents indicates leakage to earth above 25% of drive rating.
Root causes. Insulation breakdown in cable or windings; moisture in the motor terminal box after washdown or condensation; conductive dust bridging terminals.
Repair steps. Megger the cable phase-to-earth with the drive disconnected — above 10 MΩ at 1000 V is acceptable. Megger the windings and compare phases with each other rather than against a pass/fail limit. Open the terminal box, inspect for moisture, dry it out and re-test. If cable and motor are both healthy but F013 returns immediately, the drive's current sensing or output stage is faulty.
F070 trips the instant the drive is enabled and will not reset. It means an output transistor conducted in the active region instead of desaturating — a damaged IGBT, a failed gate drive circuit, or insufficient gate drive voltage. In practice the power module or gate driver board must be replaced.
F081 stops the drive mid-run or drops it to minimum frequency; F071–F076 are the equivalent port 1–6 adapter faults. Causes are a damaged network cable, missing terminating resistors, an unpowered adapter, a poorly seated DPI ribbon cable, or electrical noise. Reseat the ribbon and adapter, check the adapter LEDs, and confirm termination at both ends of the trunk.
Two more codes worth recognising: F033 (auto restart tries) is not a root cause — read the history beneath it, because it means the drive exhausted its restart attempts. F100 means corrupt non-volatile memory: restore the parameters, and replace the control board if it recurs.
Field-repairable faults: F004 (connections and power quality), F005 (ramp, resistor, chopper), F007 (FLA, load, motor), F008 (fans, fins, airflow), F013 where the megger points to cable or motor, plus F029, F033 and F081. Component-level or replacement faults: F012 and F070 where the power stage has failed, and any repeat of F100 after a parameter restore.
The economics on the 20A/20B platforms are straightforward. Component-level repair typically costs well under a new drive and is available in weeks rather than the 16–24 weeks a new PowerFlex 755 can take. Our VFD and AC drive collection carries replacement drives and spare modules; keep at least one fan assembly and one keypad on the shelf per drive family, because both are terminal items that stop a restart on their own.
Every 3 months: clean or replace air filters; inspect and clean heatsink fins. Every 6 months: confirm every fan runs at full speed and spins freely by hand; record heatsink temperature under load. Every 12 months: torque line and motor terminations; megger the motor and cable; archive a parameter backup and the fault queue, then clear it. Every 5 years: replace cooling fans as a scheduled item rather than waiting for F008, and inspect the dynamic braking resistors. Every 5–10 years: evaluate the DC bus capacitor bank — ripple in the bus voltage reading, or a bus that droops under load with stable input power, indicates degradation.
Before energising a stored drive: under two years needs no reforming; two to three years needs rated voltage for 30 minutes with no load; over three years needs a DC supply ramping 0 → 50% → 75% → 100% of DC bus voltage, 30 minutes at each step, current limited to 500 mA.
Can I clear these faults from the keypad? Yes — the Stop/Reset key, a digital input configured as fault reset, or a power cycle. Record the fault queue first; a cleared queue cannot be recovered.
F012 will not reset even with the motor disconnected. Is the drive dead? The power stage has failed. That is a component-level repair or a replacement unit; no parameter change will bring it back.
Are spare parts still available for PowerFlex 70/700 drives? Yes, though genuine 20A/20B replacement units are increasingly available only as remanufactured stock. Fans, keypads, adapters and power modules remain obtainable, and models such as 20F11ND065JA0NNNNN, 22A-A2P1N103 and 22C-B090A103 are listed in our Allen-Bradley PowerFlex replacement drives range.
