Magnetek Drive Fault Codes

OC: Over Current

What it means: Output current went above 200% of the drive's rated output current.^[3][5]

Also on: IMPULSE G+ Mini: same fault shown as oC (Over Current), same 200% trip level.

Likely causes

• Phase-to-phase short in the motor or motor wiring
• Acceleration or deceleration time too short
• Torque limits (C07-01 to C07-04) raised too high
• Erratic or missing encoder feedback, so the drive pushes more current trying to hold position

First checks, in this order

1. Check the motor and motor leads for a phase-to-phase short with an insulation tester (megohmmeter).
2. Extend the acceleration and deceleration times.
3. Check the torque limit settings C07-01 to C07-04.
4. On encoder drives, check the pulse wheel or shaft coupling alignment and the encoder cable for breaks, shorts and a poorly grounded shield.

SC: Short Circuit

What it means: The drive detected a short circuit on its output.^[3]

Likely causes

• Shorted motor winding
• Short in the motor cable or at the terminals

First checks, in this order

1. Disconnect the motor from the drive.
2. Check the motor and the motor cable for a short with an insulation tester.

F901: PCU IST FAULT

What it means: Armature current went above 300% of rated armature current (instantaneous overcurrent trip).^[1][2]

Likely causes

• Ground fault or intermittent connection in the motor armature circuit
• Faulty current measuring module
• Poor current regulator tuning
• Bad SCR gating (Magnetek application note 103 says this usually shows up as F901)

First checks, in this order

1. Check the armature circuit for grounds and loose or intermittent connections.
2. Check the current measuring module.
3. Review the current regulator tuning.
4. Check the SCR gate wire connections.

GF: Ground Fault

What it means: The drive adds up the three output phase currents; the sum went above 50% of the drive rated output current, which points to current leaking to ground.^[3]

Likely causes

• Motor winding or motor cable insulation failed to ground
• Electrical transients from brake contactor coils without surge suppression

First checks, in this order

1. Disconnect the motor from the drive and test the motor and cable insulation with an insulation tester.
2. Make sure R/C surge suppressors are fitted across all brake contactor coils.

GF: Ground Fault

What it means: Current to ground on the drive output went above 50% of rated current. On this drive, ground fault detection is switched on with L08.09 = 1 and is available on models 2025 and 4014 or larger.^[5]

Likely causes

• Motor winding or motor cable insulation failed to ground
• Electrical transients from brake contactor coils without surge suppression

First checks, in this order

1. Disconnect the motor from the drive and test the motor and cable insulation with an insulation tester.
2. Make sure R/C surge suppressors are fitted across all brake contactor coils.
3. Check that L08.09 is set as intended.

OV: DC Bus Overvolt

What it means: The main circuit DC bus voltage went above the overvoltage level. If it happens while the drive output is off (stopped), the same code shows as an alarm instead of a fault.^[3]

Likely causes

• Deceleration too fast, so regenerated energy pumps up the DC bus
• Braking unit (DBU) or braking resistor not working or wrong size
• High incoming line voltage (the usual cause when it appears while stopped)

First checks, in this order

1. Extend the deceleration time.
2. Check braking unit (DBU) operation.
3. Check the braking resistor.
4. Check the line voltage.

oV: DC Bus Overvolt

What it means: DC bus voltage went above about 410 V DC on 230 V class drives or about 820 V DC on 460 V class drives. A flashing oV means it happened while the output was off (minor fault).^[5]

Likely causes

• Deceleration too fast for the load
• Braking unit (DBU) or braking resistor problem
• High incoming line voltage
• On a mechanical load brake hoist, a gear box problem

First checks, in this order

1. Extend the deceleration time.
2. Check braking unit (DBU) operation and the braking resistor.
3. Check the line voltage.
4. If it is a load brake hoist, check the gear box.

F408: EXCESSIVE PCU CEMF FAULT

What it means: Motor counter EMF went above 118% of the rated AC input voltage, so the drive shuts down to keep from blowing fuses.^[1]

Likely causes

• Low 3-phase input voltage
• Motor field current set too high, or the field regulator misbehaving
• Speed overshoot
• Field control tuning that lets CEMF overshoot

First checks, in this order

1. Measure the 3-phase input voltage and correct it.
2. Review the field settings #49, #50, #51, #52, #54 and #55.
3. Correct speed overshoot with the velocity regulator adjustments.

UV1: DC Bus Undervolt

What it means: DC bus undervoltage lasted more than 2 seconds while a RUN command was present.^[3]

Likely causes

• Low or lost supply voltage
• Loose power wiring
• Crane collector system (runway conductors) losing contact

First checks, in this order

1. Check the power wiring.
2. Correct the line voltage.
3. Check the collector system.

UV: DC Bus Undervolt

What it means: DC bus undervoltage lasted more than 2 seconds while the drive was stopped. Shown as an alarm.^[3]

Likely causes

• Low or lost supply voltage
• Blown branch fuse
• Crane collector system losing contact

First checks, in this order

1. Check the power wiring.
2. Replace any blown branch fuses.
3. Check the collector system.

Uv1: DC Bus Undervolt

What it means: Undervoltage lasted more than 2 seconds with a RUN command present. The trip level is below about 190 V DC on 230 V class drives and 380 V DC on 460 V class drives.^[5]

Likely causes

• Low or lost supply voltage
• Loose power wiring
• Crane collector system losing contact

First checks, in this order

1. Check the power supply wiring.
2. Correct the line voltage.
3. Check the collector system.

Uv: DC Bus Undervolt

What it means: Flashing Uv: undervoltage lasted more than 2 seconds while stopped, with the same voltage levels as Uv1 (about 190 V DC on 230 V class, 380 V DC on 460 V class).^[5]

Likely causes

• Low or lost supply voltage
• Blown branch fuse
• Crane collector system losing contact

First checks, in this order

1. Check the power source wiring.
2. Replace any blown branch fuses.
3. Check the collector system.

F904: LOW LINE FAULT

What it means: AC input dropped below 80% of the nominal line voltage set in #9 for 3 cycles in a row, or below 50% for one cycle. The current reference is forced to zero and the drive shuts down.^[1][2]

Likely causes

• Supply voltage sag or outage
• Loose or failing connection upstream (breaker, transformer, fuses)
• #9 NOMINAL AC INPUT not matching the real line voltage

First checks, in this order

1. Measure the 3-phase input under load and check the upstream breaker, transformer and fuse connections.
2. Confirm #9 matches the real line voltage.
3. Do not set #9 lower than the real voltage to hide this fault; Magnetek notes this pushes the drive into CEMF limiting and ripple faults (F909).

F406: 10% LOW LINE ALARM

What it means: AC input sagged more than 10% below the nominal voltage in #9. The drive keeps running, but it is an early sign of future F904 shutdowns.^[1]

Likely causes

• Weak or drooping supply
• Upstream connection or transformer problem
• #9 set higher than the real line voltage

First checks, in this order

1. Check the incoming supply and connections before it turns into F904 trips.
2. Confirm #9 NOMINAL AC INPUT is correct.

F903: LINE SYNC FAILURE

What it means: The drive's phase-locked loop lost sync with the 3-phase input. The drive shuts down and needs a CPU reset. It often appears together with F904.^[1][2]

Likely causes

• AC input power disturbances
• Pulsating armature current from poor tuning that disturbs the supply as seen by the drive (application note 103)

First checks, in this order

1. Check the AC input power quality and connections.
2. Look for F904 in the fault list at the same time.
3. If it comes with F909, review the tuning: inertia #41 and stiffness #42.

UV2: CTL PS Undervolt

What it means: The drive lost its internal 24 V logic power supply voltage.^[3][5]

Also on: IMPULSE G+ Mini: same fault shown as Uv2 (CTL PS Undervolt).

Likely causes

• Low or interrupted supply voltage
• Power wiring or collector system problem

First checks, in this order

1. Check the power wiring.
2. Correct the line voltage.
3. Check the collector system.

UV3: MC Answerback

What it means: The pre-charge contactor opened while the drive was running.^[3][5]

Also on: IMPULSE G+ Mini: same fault shown as Uv3 (MC Answerback).

Likely causes

• Supply voltage dip or interruption
• Power wiring or collector system problem

First checks, in this order

1. Check the power wiring.
2. Correct the line voltage.
3. Check the collector system.
4. Wait 30 to 45 seconds before restarting the drive.

F902: POWER SUPPLY FAULT

What it means: The low voltage power supply (A4) output fell below 60% of rated. The drive shuts down and needs a CPU reset.^[1]

Likely causes

• Loss of 115 VAC control power
• Short on the +5 V, +/-15 V or +24 V circuits, possibly in wiring outside the drive
• Failed power supply
• Blown fuse inside the power supply

First checks, in this order

1. Check the 115 VAC control power at TB3 of power supply A4.
2. Look for shorts on external logic wiring powered by the drive.
3. Replace the power supply if the fault stays.

OH: Heatsnk Over temp

What it means: Overheat pre-alarm: heatsink temperature passed the level set in L08-02. The manual marks it as alarm or fault; L08-03 picks what the drive does.^[3][5]

Also on: IMPULSE G+ Mini: shown as flashing oH (Heatsnk Over temp), level set in L08.02.

Likely causes

• Drive cooling fan stopped
• High ambient temperature

First checks, in this order

1. Check that the drive cooling fan runs.
2. Reduce the ambient temperature.
3. Check L08-02 and L08-03.

OH1: Heatsink MaxTemp

What it means: Overheat fault: the measured heatsink temperature went above 105 °C, or the internal 24 V DC cooling fan failed.^[3][5]

Also on: IMPULSE G+ Mini: same fault shown as oH1 (Heatsink MaxTemp), same 105 °C level.

Likely causes

• Cooling fan failure
• Dirt and debris on the heatsink
• Ambient temperature above specification
• Faulty heatsink thermistor

First checks, in this order

1. Make sure the heatsink cooling fans run.
2. Clean dirt and debris off the heatsink.
3. Check that the ambient temperature is within specification.
4. Replace the 24 V DC fan, then the heatsink thermistor(s) if the fault stays.

F908: OVER TEMPERATURE

What it means: The calculated SCR junction temperature is above 125 °C, worked out from the heatsink thermistor and the armature current. The manual says it does not shut the drive down.^[1]

Likely causes

• Ambient temperature too high
• Clogged cabinet air filter
• Clogged heatsink fins
• Failed cooling fan in the power cube
• Leakage between the heatsink thermistor and its leads (false readings)

First checks, in this order

1. Check the machine room temperature.
2. Clean or replace the cabinet air filter.
3. Clean the heatsink fins.
4. Replace failed cooling fans.
5. If it repeats with no real heat, replace the thermistor and thermostats.

FAn: Cooling FAN Err

What it means: The internal cooling fan has malfunctioned. L08-32 sets whether it acts as a fault or an alarm.^[3]

Likely causes

• Worn or blocked cooling fan
• Fan at the end of its service life

First checks, in this order

1. Cycle power to the drive.
2. Check that the fan runs.
3. Check fan run time in U04-03 and the fan maintenance timer in U04-04.
4. Replace the fan.

OL1: Motor Overloaded

What it means: Drive output went above the motor overload level. The manual lists it as fault or alarm.^[3][5]

Also on: IMPULSE G+ Mini: same fault shown as oL1 (Motor Overloaded); setting is E02.01.

Likely causes

• Load too high
• Motor full load amps (E02-01) set wrong

First checks, in this order

1. Check that E02-01 matches the motor nameplate full load amps.
2. Reduce the load.

OL2: VFD Overloaded

What it means: Drive output went above the drive's own overload level. The manual lists it as fault or alarm.^[3][5]

Also on: IMPULSE G+ Mini: same fault shown as oL2 (VFD Overloaded).

Likely causes

• Load too high for the drive size
• Acceleration time too short

First checks, in this order

1. Reduce the load.
2. Extend the acceleration time.

F400: MOTOR OVERLOAD

What it means: The drive has delivered too much motor current for too long (electronic motor overload). It does not stop the drive; it switches the ALARM relay output K2 so the car controller can act.^[1]

Likely causes

• Dragging elevator brake
• Weakened motor field
• Overload time or level set wrong

First checks, in this order

1. Check #83 MOTOR OVERLD TIME and #84 MOTOR OVERLD LEVEL.
2. Check the elevator brake for drag.
3. Check the motor field.
4. See #182 for the alarm relay setting.

OH3: Motor Overheat 1

What it means: The motor thermistor on the analog input reports motor overheating at the alarm level (L01-03). OH4 (Motor Overheat 2) is the fault level, set in L01-04.^[3][5]

Also on: IMPULSE G+ Mini: same codes oH3 and oH4 (settings L01.03 and L01.04).

Likely causes

• Motor working too hard for its duty cycle
• Motor rated current (E02-01) set wrong

First checks, in this order

1. Check the motor rated current value in E02-01.
2. Increase the cycle time or reduce the load.

oL8: Klixon

What it means: Klixon circuit alarm: the motor thermal switch circuit, wired to a digital input set to 56 or 57 (H01.xx), has opened.^[5][3]

Also on: IMPULSE G+ / VG+ Series 4: same alarm shown as KLX (Klixon), input H01-0x = 56 or 57.

Likely causes

• Motor overheating
• Open or loose Klixon circuit wiring

First checks, in this order

1. Check the motor for overtemperature.
2. Check the Klixon circuit.

F941: MOTOR THERMOSTAT OPEN

What it means: The drive sees the motor thermostat open between A4TB3(2) and A4TB3(8). It does not stop the drive; it switches the ALARM relay output K2.^[1]

Likely causes

• Motor overheated
• Open thermostat wiring
• Faulty power supply input (if the circuit is closed but the fault stays)

First checks, in this order

1. Let the motor cool and check the thermostat and its wiring to A4TB3.
2. If the circuit is closed but the fault stays, replace the power supply.
3. See #182 for the alarm relay setting.

PF: Input Phase Loss

What it means: One phase of the drive's input power supply is open.^[3][5]

Also on: IMPULSE G+ Mini: same fault shown as PF (Input Pha Loss).

Likely causes

• Blown line fuse
• Loose input terminal
• Lost supply phase

First checks, in this order

1. Check the line voltage and fuses.
2. Remove power and tighten the input terminals.

F910: BLOWN FUSE

What it means: One or more of the three AC line fuses is open. Checked at power-up and during PCU Diagnostics (#998); at power-up the SCDU marks each blown fuse with the middle segment of a display digit.^[1]

Likely causes

• Blown AC input fuse
• Power wiring problem
• Faulty DSPR power relay

First checks, in this order

1. Remove power and check the line fuses.
2. Check the power wiring.
3. If all fuses test good, make sure 3-phase power and control power come on together (or the controller resets the drive after 3-phase power is applied).
4. Check the power supply test points TP1 to TP4 on the Drive Control PCB: +24 V, +15 V, -15 V, +5 V within 5%.

LF: Output Phase Loss

What it means: An open phase occurred on the drive output.^[3][5]

Also on: IMPULSE G+ Mini: same fault shown as LF (Output Phase Loss).

Likely causes

• Broken wire in the output cable
• Open motor winding
• Loose terminal

First checks, in this order

1. Check the output cable for broken wires.
2. Check the motor for an open winding.
3. Check for loose terminals.

F404: OPEN ARMATURE CIRCUIT FAULT

What it means: A large current error lasted half a second, which usually means the armature circuit is open.^[1]

Likely causes

• Blown DC link fuse F4
• Open or loose armature wiring
• Bad power poles in the DC loop contactor

First checks, in this order

1. Check DC link fuse F4.
2. Check the motor armature circuit wiring.
3. Check the power poles in the DC loop contactor.

PGO-1-S / PGO-1-H: PG Open Ch1

What it means: Encoder (pulse generator) feedback lost on the PG-X3 card in connector CN5-C: -S is found by software, -H by hardware. PGO-2-S and PGO-2-H mean the same for a card in CN5-B. F01-21 sets the stopping method or alarm only.^[3]

Likely causes

• No encoder pulses while the drive is commanded to run
• Broken or shorted encoder wiring
• Misaligned pulse wheel, loose shaft coupling or failed sensor head
• Brake not opening, so the motor cannot turn

First checks, in this order

1. Do not keep running the hoist after a PGO-x-H fault or repeated PGO-x-S faults.
2. As a precaution, set Load Float Time C08-10 to zero until the cause is fixed.
3. Check the pulse wheel alignment, shaft coupling and sensor head.
4. Check each encoder wire for continuity, shorts between wires and shorts to shield or ground.
5. Check that the brake opens, then restore C08-10.

DEV: Speed Deviation

What it means: The gap between speed reference and encoder speed stayed above F01-27 for longer than F01-28, so the drive cannot follow the commanded speed. F01-26 sets fault or alarm.^[3]

Likely causes

• Drive at its torque limit
• Snagged load or load above capacity
• Erratic or missing encoder pulses
• Brake not opening fully
• Acceleration or deceleration times shortened

First checks, in this order

1. Stop using the hoist until the cause is found; set C08-10 to zero meanwhile.
2. Check for a snagged load or a load above capacity.
3. Check the encoder pulse wheel, coupling and cable.
4. Check that the brake opens fully.
5. Check accel and decel times B05-01, B05-02, C01-02, C01-04 and C01-05.
6. Only after all that, raise F01-27, to no more than 30%.

OS: Over Speed

What it means: The motor went above the overspeed level (F01-24) for the set time (F01-25). It is usually overshoot from a speed loop tuned too aggressively, or torque control mode running with no load. F01-23 sets the action.^[3]

Likely causes

• Over-responsive speed regulator (ASR)
• Torque control mode with no load on the hook
• Wrong encoder pulses per revolution setting

First checks, in this order

1. Check the speed regulator settings in group D04.
2. Check F01-24 and F01-25.
3. Check the encoder PPR in F01-01.

F97: OVERSPEED TRIP

What it means: Encoder speed went above the trip level in #12, a percentage of rated motor RPM in #11.^[1]

Likely causes

• #10, #11 or #12 set wrong
• Poor speed regulator tuning
• Speed reference above rated speed
• Intermittent encoder

First checks, in this order

1. Check #10 ENCODER PPR, #11 RATED MOTOR RPM and #12 OVERSPEED %.
2. Check speed regulator tuning #40, #41 and #42.
3. Check that the speed reference does not exceed rated speed.
4. Check the encoder and its connections.
5. For a governor overspeed test, temporarily raise #12 above the governor trip speed.

F98: TACH/ENCODER LOSS

What it means: Encoder speed does not match the speed the drive expects from the armature voltage.^[1]

Likely causes

• Encoder not working or loose connection
• High motor resistance
• Contactor feedback at A1TB1-7 closing before the armature power poles

First checks, in this order

1. Check that the encoder works and look for loose connections.
2. On a high resistance motor, raise #14 V SENSE %; see also #15 T SENSE %.
3. Make sure the contactor feedback at A1TB1-7 does not close before the armature power poles.

F99: REVERSE TACH/ENCODER

What it means: The encoder and the motor voltage disagree on direction of rotation.^[1]

Likely causes

• Encoder leads reversed

First checks, in this order

1. Swap the encoder A and A NOT connections.

F410: SPEED ERROR FAULT

What it means: A speed error larger than #100 lasted longer than #99 seconds, so the drive shut down.^[1]

Likely causes

• Dragging brake
• Weak motor field
• Trip time or level set too tight

First checks, in this order

1. Check the brake for drag.
2. Check the motor field.
3. Check #99 SPEED ERROR TRIP TIME and #100 SPEED ERROR TRIP LEVEL.

BE1: Rollback Detect

What it means: After releasing the brake but before accelerating, the drive counted more encoder pulses than C08-05 within C08-04: the load rolled back. Usually the motor did not have enough torque to hold the load.^[3]

Likely causes

• Not enough torque at brake release
• Noisy or damaged encoder cable
• Misaligned pulse wheel or loose shaft coupling

First checks, in this order

1. Check the encoder cable for damage, noise and shield grounding.
2. Check the pulse wheel and shaft coupling alignment.
3. Only then adjust: keep C08-05 as close to 800 pulses as possible, and increase C08-21.

BE2: No Current

What it means: Torque proving fault: before releasing the brake, the drive could not build torque up to C08-16 within the C08-02 timer. This often means a failed or slipping brake.^[3]

Likely causes

• Brake slipping, worn or out of adjustment
• Motor not auto-tuned
• Open power limit switch
• Encoder cable or alignment problem

First checks, in this order

1. Do not switch power off while it is active; move the load to a safe spot and lower it.
2. Check brake operation, adjustment and wear, and run a brake torque test.
3. Make sure the motor was auto-tuned and any power limit switch is closed.
4. Check the encoder cable and pulse wheel alignment.
5. Only then adjust: C08-02 not below 0.5 s, C04-02 not below 5, C08-16 not below 50.

BE3: Brake Release NG

What it means: After releasing the brake and starting, the drive saw fewer encoder pulses than C08-07 within C08-06: the motor did not turn as expected. The load may drift until the brake sets again.^[3]

Likely causes

• Brake not opening
• Misaligned pulse wheel or loose coupling
• Damaged encoder cable

First checks, in this order

1. Check that the brake opens.
2. Check the pulse wheel and coupling alignment.
3. Check each encoder wire for continuity and shorts.
4. Only then adjust: set C08-04 to the brake's mechanical delay, raise C08-06 to no more than 1 s, lower C08-07 to no less than 10 pulses.

BE4: Brake Answer 1

What it means: At start, the brake answerback input did not arrive within C08-04 after the brake release command, so the brake is not confirmed released. The manual lists it as alarm and fault.^[3][5]

Also on: IMPULSE G+ Mini: shown as flashing BE4 (Brake Answer 1), setting C08.04.

Likely causes

• Brake not releasing
• Fault in the brake answerback (feedback) circuit
• C08-04 shorter than the brake's real release time

First checks, in this order

1. Check the brake answerback circuit.
2. Increase C08-04.
3. Check the input status in U01-10.

BE5: Brake Answer 2

What it means: At stop, the brake answerback signal did not drop within C08-11 after the brake release command was removed, so the brake is not confirmed closed. It becomes a fault only if latched (L09-07, L09-08).^[3][5]

Also on: IMPULSE G+ Mini: shown as flashing BE5 (Brake Answer 2), setting C08.11.

Likely causes

• Brake not setting
• Stuck brake answerback contact or wiring fault
• C08-11 shorter than the brake's real closing time

First checks, in this order

1. Check the brake answerback circuit.
2. Increase C08-11.

BE6: Brake Slipping

What it means: Brake proving alarm: after commanding the brake to set, the drive counted more than C08-13 encoder pulses within C08-12, so the load is moving against the brake. The drive holds the load with Load Float during the alarm. It becomes a fault only if latched.^[3][4]

Likely causes

• Failed, worn or badly adjusted brake
• Noisy or damaged encoder cable
• Misaligned pulse wheel or loose coupling

First checks, in this order

1. Do not switch power off; move the load to a safe spot and lower it.
2. Check brake operation, adjustment and wear.
3. Check the encoder cable and the pulse wheel or coupling alignment.
4. Only then adjust: set C08-11 to the brake's mechanical delay and increase C08-13.

BE7: Brake Welded

What it means: At power-up the brake answerback is already on, which says the brake is not closed (or the answerback is stuck on).^[3]

Likely causes

• Brake held open
• Welded or stuck answerback contact
• Answerback wiring fault

First checks, in this order

1. Check that the brake is closed.
2. Check the brake answerback circuitry.

BE8: Brake Slipping

What it means: While not running, the encoder shows the load moving faster than C08-23 with the brake set. The drive goes into Load Float and keeps the brake closed. It becomes a fault only if latched.^[3][4]

Likely causes

• Failed, worn or badly adjusted brake
• Noisy or damaged encoder cable
• Misaligned pulse wheel or loose coupling

First checks, in this order

1. Do not switch power off; move the load to a safe spot and lower it.
2. Check brake operation, adjustment and wear.
3. Check the encoder cable and alignment.
4. Check C08-23; if everything else checks out, the brake may need replacing.

BE0: Brake Ans Lost

What it means: While running, the brake answerback input (H01-0x = 58) was lost. The manual lists it as alarm and fault.^[3][5]

Also on: IMPULSE G+ Mini: shown as flashing BE0 (Brake Ans Lost).

Likely causes

• Brake answerback switch or wiring fault
• Brake starting to set during the run

First checks, in this order

1. Check the brake answerback circuit.
2. Check the input status in U01-10.

DIR: Direction Fault

What it means: The drive found the hoist set up so that the FWD direction moves the hook DOWN.^[3]

Likely causes

• Motor phase order or B03-04 setting gives the wrong direction
• Encoder direction not matching motor direction

First checks, in this order

1. Verify the keypad shows FWD while moving UP; change B03-04 if it shows REV.
2. Once the travel direction is verified correct, C08-34 = 0 disables DIR detection.

SNAP: Snapped Shaft

What it means: A break in the drive train was detected by comparing two encoders (needs a second PG-X3 card). C11-09 sets fault or alarm.^[3]

Likely causes

• Loose or broken coupling
• Loose encoder
• Broken shaft

First checks, in this order

1. Check for a loose or broken coupling.
2. Check for loose encoders.
3. Check for a broken shaft.

F402: CONTACTOR FAULT

What it means: The loop contactor auxiliary contact did not pick up or drop out within the allowed time (#102 selects the detection time).^[1]

Likely causes

• Defective loop contactor auxiliary contact
• Contactor coil open or mechanically binding
• Defective pilot relay LPR
• Interference from other elevator relay contact circuits

First checks, in this order

1. Check for proper feedback at TB1-7.
2. Check the contactor for an open coil or binding.
3. Check pilot relay LPR.
4. Check #102 3S LOOP FLT.

F900: PCU LOOP FAULT

What it means: The loop contactor did not close or opened unexpectedly, or motor voltage went above 30% of rated (#7) during Self-Tune (#997). The current reference is forced to zero and the drive shuts down.^[1]

Likely causes

• Contactor auxiliary feedback circuit fault
• Contactor or LPR coil problem
• No power to LPR from the power supply (internal relay failure)

First checks, in this order

1. Check the contactor auxiliary feedback circuit to TB1-7.
2. Check the contactor and LPR coils.
3. Check that LPR gets power from the power supply at TB3-5 (only momentary until F900 occurs); if not, replace power supply PCB A4.

F405: SAFETY CIRCUIT FAULT

What it means: The safety circuit wired between TB3-1 and TB3-6 on the power supply opened unexpectedly while the drive was running. The check is off below the low speed threshold (#64).^[1]

Likely causes

• Intermittent connection in the safety chain
• Safety chain closing less than 100 ms before the drive is enabled

First checks, in this order

1. Check the safety chain for intermittent connections.
2. Make sure the safety chain is closed at least 100 ms before the drive is enabled.

CE: Serial Com Err

What it means: Serial communication was disrupted. The manual lists it as fault or alarm, set by the serial fault parameters in group H05.^[3][5]

Also on: IMPULSE G+ Mini: CE (Modbus Com Err), serial data corrupted; check terminals R+, R-, S+, S- and H05.01 to H05.03 (the G+ Mini manual writes its parameters with a dot).

Likely causes

• Loose or damaged serial cable
• Wrong address, baud rate or parity
• Electrical noise on the communication line

First checks, in this order

1. Check the serial connections.
2. Check H05-01 to H05-05.

F117: 10 SEC COMM. START FAULT

What it means: Serial communication did not start within 10 seconds after drive reset or power-up.^[1]

Likely causes

• Host (car controller) not connected or not sending valid messages
• Grounding or noise problem on the serial link
• #110 set to serial mode (3) when serial control is not used

First checks, in this order

1. Make sure the host is connected and sending valid messages.
2. Look for and correct grounding and noise problems.
3. If serial communication is not used, do not set #110 to 3.

F118: 150 MSEC COMM. MSG FAULT

What it means: No valid serial message was received for more than 150 ms.^[1]

Likely causes

• Host stopped sending or sends bad messages
• Grounding or noise problem on the serial link

First checks, in this order

1. Make sure the host is connected and sending valid messages.
2. Look for and correct grounding and noise problems.
3. If serial communication is not used, do not set #110 to 3.

RR: DynBrk Transistr

What it means: The internal braking transistor has failed.^[3][5]

Also on: IMPULSE G+ Mini: same fault shown as rr (DynBrk Transistr).

Likely causes

• Braking resistor wired to the wrong terminals
• Wrong braking resistor
• Short circuit across the braking resistor

First checks, in this order

1. Verify the external braking resistor is connected to the proper terminals.
2. Confirm the proper resistor is installed.
3. Check for a short circuit across the braking resistor.

F401: EXCESSIVE FIELD CURRENT

What it means: Measured motor field current went above 125% of rated field current (#50).^[1]

Likely causes

• Partially shorted motor field coil
• Wrong settings making the field current regulator unstable
• Wrong phasing on field module A3
• Wrong current tap at A3 TB4 or wrong A3 SW1 setting
• Motor field power circuit malfunction

First checks, in this order

1. Check the motor field.
2. Review #49, #50, #51, #52, #54 and #55.
3. Verify A3 phasing, the TB4 current tap and SW1.
4. Check module A3.

F905: FIELD LOSS

What it means: Field current feedback fell below 80% of the expected value: #49 at top speed (field weakening), #50 during accel and decel (full field), #53 when standing. The drive shuts down.^[1]

Likely causes

• Open motor field or field wiring
• Motor field control hardware failure
• Loss of power or wrong phasing to the field rectifier

First checks, in this order

1. Check the motor field and its wiring for an open circuit.
2. Check the AC supply and phasing to the field rectifier.
3. Check the field control module.

F403: 5-MIN FULL FIELD FAULT

What it means: The Drive and Field Enable input at TB1-9 stayed on for 5 minutes without the drive starting, which risks burning out the motor field.^[1]

Likely causes

• Car controller relay logic leaving the enable on while idle

First checks, in this order

1. Check the car controller relay logic that drives TB1-9.

F407: EXCESSIVE DCU CEMF ALARM

What it means: Motor CEMF went above 109% of the measured AC input voltage. Warning only; the drive keeps running.^[1]

Likely causes

• 3-phase input voltage drooped or is too low
• Motor field current too high (#49 weak field set point vs. desired top speed voltage)
• Field control tuning letting CEMF overshoot

First checks, in this order

1. Check the input voltage.
2. Check #49 against the motor voltage you want at top speed.
3. Review #49, #50, #51, #52, #54 and #55.

F909: EXCESSIVE RIPPLE

What it means: Armature current repeatedly showed a high peak-to-average ratio. Magnetek added it to protect motors from running on a missing SCR phase.^[1][2]

Likely causes

• Poor tuning: inertia #41 too high, stiffness #42 or tach rate gain #107 too high
• Drive running into the CEMF limit
• Open SCR or loose gate wires
• Off-center encoder mounting
• Loose connections upstream, in the armature loop or worn motor brushes
• Repeated mechanical bumps in the hoistway

First checks, in this order

1. Run PCU Diagnostics (#998) to look for hardware faults.
2. Review tuning #41, #42 and #107.
3. Check that the encoder is concentric with the motor shaft.
4. Check 3-phase connections, the armature loop, brushes and SCR gate wires.
5. Make sure all contactor and relay coils have noise suppressors.

F911: SHORTED SCR

What it means: PCU Diagnostics (#998) found a short between the SCRs of an SCR/doubler pack. It is only checked when diagnostics run, and the drive must be powered down. F912 OPEN SCR is the companion result for an SCR that does not conduct.^[1]

Likely causes

• Failed SCR or doubler pack

First checks, in this order

1. Run PCU Diagnostics (#998); the optional handheld PCDU shows which SCR pair is bad.
2. Replace the bad SCR pack.
3. For F912, also check the SCR gate leads.

F411: MAX AUTO-RESETS ATTEMPTED

What it means: More than 5 automatic resets were needed within 20 minutes of accumulated time, so auto reset (#101) stops and a manual reset is needed.^[1]

Likely causes

• A repeating underlying fault

First checks, in this order

1. Find the repeating fault in the Fault List (Function #0) or Error List (#800) and fix it.
2. Reset the drive manually.

F926: PCU WATCHDOG TIMEOUT FAULT

What it means: The power conversion processor was reset by its own watchdog timer. Usually caused by electrical noise. The drive must be powered down.^[1]

Likely causes

• Electrical noise from relays without suppression
• 115 VAC and 24 VDC switched in the same relay without arc barriers
• Intermittent grounds in power or 24 VDC wiring
• Faulty EPROMs or sockets at U13, U14, U39 or U40

First checks, in this order

1. Make sure all panel relays, including door operator relays, have working R/C coil suppression.
2. Separate 115 VAC and 24 VDC contacts or add arc barriers.
3. Check for intermittent grounds and verify the Drive Control PCB grounding and encoder wiring.
4. Check the EPROMs and their sockets.

Prot: CORRUPTED NV RAM DATA

What it means: At power-up the drive found parameter data lost or new (weak NVRAM battery in U56, new software or a new NVRAM chip) but cannot load defaults because the NV RAM PROTECT switch is on.^[1]

Likely causes

• Weak battery inside NVRAM chip U56
• Software or NVRAM chip changed

First checks, in this order

1. Set the NV RAM PROTECT switch to OFF and press CPU RESET to load defaults.
2. Re-enter the parameters and save them with Function #994, then set the switch back to ON.
3. Replace U56 every 8 years.

CPF06: EEPROM Error

What it means: Data saved in EEPROM is corrupt, from an EEPROM circuit error or from power being switched off while parameters were saving.^[3][5]

Also on: IMPULSE G+ Mini: CPF06 (EEPROM Data Error); cycle power, replace the drive if it stays.

Likely causes

• EEPROM or control circuit fault
• Power lost during a parameter save

First checks, in this order

1. Turn off power and check the connection between the control board and the drive.
2. After an interrupted save, reinitialize with A01-05 = 5432.
3. If it continues, replace the control board or the drive (contact Magnetek).

HBB / HBBf: Hardware Base Block

What it means: One of the Safe Disable inputs (H1, H2) is open, so the output is off, the motor coasts and the brake relay output opens.^[3][5]

Also on: IMPULSE G+ Mini: Hbb (Hardware BB); if Safe Disable is not used, check that terminals HC and H1 are linked.

Likely causes

• External safety circuit opened
• Wrong sink/source selection for the digital inputs
• H1 and H2 jumpers missing when Safe Disable is not used

First checks, in this order

1. Check the signal status at input terminals H1 and H2.
2. Check the sink/source selection for the digital inputs.
3. If Safe Disable is not used, check the H1 and H2 jumpers.
4. If all is correct, replace the control board or the drive.

BB: Base Block

What it means: A digital input commanded external base block: the output is off and the motor coasts. If RUN is still on when the base block input clears, the drive resumes at the commanded speed.^[3][5]

Also on: IMPULSE G+ Mini: shown as flashing bb (Base Block); check H01.01 through H01.07.

Likely causes

• Base block input active
• Digital input programmed for base block by mistake

First checks, in this order

1. Check H01-01 through H01-08 programming.
2. Check the input status in U01-10.

EF1 to EF8: External Fault 1 to External Fault 8

What it means: An external device wired to input terminal S1 to S8 signaled a fault; the number is the terminal. Fault or alarm is set in the External Fault Selection table.^[3][5]

Also on: IMPULSE G+ Mini: EF1 to EF7 for terminals S1 to S7 (H01.01 to H01.07).

Likely causes

• Fault in the external device wired to that input
• Input programmed as external fault by mistake

First checks, in this order

1. Check the programming of the matching input (H01-01 for S1 through H01-08 for S8).
2. Check the condition of that input terminal (U01-10).
3. Check the external device.

CF: Control Fault

What it means: In Open Loop Vector control, the torque limit was reached for 3 seconds or longer.^[5]

Likely causes

• Motor data not tuned
• Wrong motor parameters

First checks, in this order

1. Perform auto-tuning.
2. Check the motor parameters (E02 group) against the nameplate.

CRST: Cannot reset

What it means: A fault reset was tried before the motor came to a complete stop, or while a RUN command was present during a fault.^[5]

Likely causes

• Reset pressed while the motor was still coasting
• RUN command held during the reset

First checks, in this order

1. Wait for the motor to come to a complete stop.
2. Reset the fault before giving a RUN command.

dnE: Drive not ready

What it means: A FWD or REV run command was already present when the drive powered up, so it will not run until the command is removed.^[5][3]

Also on: IMPULSE G+ / VG+ Series 4: shown as Cant Run (Drive Not Ready), an alarm; toggle the run command, check H01-01 to H01-08, or set B03-10 to allow run at power up.

Likely causes

• Run command held on at power-up
• Input programming error

First checks, in this order

1. Check the input terminals.
2. Check H01.01 to H01.07 programming.