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Fault code lookup

Mitsubishi FR-D700 fault codes: what they mean and what to check first

What the common FR-D700 fault codes mean, what usually causes them and what to check first – written in plain English from Mitsubishi Electric's own instruction manual, which stays the reference.

By Kunj Tapiawala, KIV Parts · Published · 8 min read

Quick answer

An FR-D700 fault shows on the operation panel as E. and a short code – for example E.OC1: the inverter shuts off its output, sends its fault signal and stays stopped until it is reset. Warnings such as OL or TH and the FN fan alarm leave the output on, but the manual says an ignored warning leads to a fault. UV is listed as a warning yet stops the output until the supply voltage recovers, and SA means the safety stop is holding it off. Find the code below, fix the cause, make sure the start signal is off, then reset with the STOP/RESET key, the RES input or a power cycle.

Jump to a code:

Safety first: lock out and tag out the inverter and the machine before you open the inverter or touch the wiring, and follow Mitsubishi Electric's precautions in the manual. The smoothing capacitors stay charged after power is removed: the manual says to wait at least 10 minutes after the power is switched off and check that the operation panel display is off; then a qualified person verifies zero voltage with a properly rated meter, checking the meter on a known source before and after, and confirms that the voltage between main circuit terminals P/+ and N/– is no more than 30 V DC (safety instructions and pp. 50, 276) – a dark display alone doesn't mean it's safe. Never bypass the safety stop inputs (S1, S2) or any other safety circuit, and never switch off a fault or raise the retry count to keep a machine running – the retry function restarts the motor by itself. The STOP/RESET key may not stop the output with some settings, so the machine needs its own emergency stop. Only qualified personnel should work on inverters, and any measurement on energized equipment follows your site's live-work and arc-flash rules.

Reading and resetting an FR-D700 fault

  1. Note the code. The operation panel's fault history shows the last eight faults, each with the output frequency, current, voltage and energization time when it happened (manual p. 252). Er.CL clears the history.
  2. Look it up in the table below – each row gives the manual page – and fix the cause first: a fault whose cause is still there comes straight back.
  3. Reset it: turn the start signal (STF / STR) off first – the manual warns that resetting with the start signal still on starts the motor without warning – then press STOP/RESET, turn on the RES signal for more than 0.1 s, or switch the power off and back on once the panel has gone dark (p. 256). The inverter is ready about 1 s after the reset.
  4. Watch the restart. If the same code returns, go back through the checks before resetting again.

The table follows the FR-D700 Instruction Manual (Applied), revision H, for the FR-D720, FR-D740, FR-D720S and FR-D710W; the page numbers are the manual's printed page numbers. Codes marked “Off in the initial setting” only appear once their function has been turned on in the parameter named in the row.

Common FR-D700 fault codes

This list covers the codes technicians run into most often, not every code. The manual has the complete list and the full corrective actions.

CodeWhat it meansLikely causesFirst checks
E.OC1Overcurrent trip during accelerationFaultManual p. 261 Output current reached about 200 % of the rated current while the motor was accelerating.
  • Acceleration time too short for the load
  • A short or ground fault on the output wiring or in the motor
  • Pr.3 [Base frequency] at 60 Hz for a 50 Hz motor, or the stall prevention level set too high
  • Lengthen Pr.7 [Acceleration time]
  • With power locked out and the DC bus confirmed discharged, inspect the output wiring and the motor for a short or ground fault
  • If it trips at every start, the manual's next step is starting with the motor disconnected (done locked out)
  • Still tripping with the motor disconnected: the manual says to contact your Mitsubishi sales representative
E.OC2Overcurrent trip during constant speedFaultManual p. 261 Output current reached about 200 % of the rated current while running at a steady speed.
  • A sudden load change or a jam
  • A short or ground fault on the output side
  • Stall prevention level set too high, or the fast-response current limit turned off
  • Keep the load steady and check the machine for jams
  • With power locked out and the DC bus confirmed discharged, inspect the output wiring and the motor
  • Review Pr.22 [Stall prevention operation level] and the fast-response current limit (Pr.156)
E.OC3Overcurrent trip during deceleration or stopFaultManual p. 262 Output current reached about 200 % of the rated current while slowing down or stopped.
  • Deceleration time too short
  • A mechanical motor brake closing too early
  • A short or ground fault on the output side
  • Lengthen Pr.8 [Deceleration time]
  • Check when the mechanical brake engages
  • With power locked out and the DC bus confirmed discharged, inspect the output wiring and the motor
E.OV1Regenerative overvoltage trip during accelerationFaultManual p. 262 Regenerated energy pushed the internal DC bus voltage over its limit while the motor was accelerating.
  • A load that drives the motor as it speeds up, for example lowering on a hoist
  • Pr.22 [Stall prevention operation level] set too low
  • A surge on the supply
  • Pr.52 = 12 shows the DC bus peak of the last run; the next start clears it (manual p. 132)
  • The manual suggests a shorter acceleration time here
  • Use the regeneration avoidance function (Pr.882, Pr.883, Pr.885, Pr.886)
E.OV2Regenerative overvoltage trip during constant speedFaultManual p. 262 Regenerated energy pushed the internal DC bus voltage over its limit while running at a steady speed.
  • The load driving the motor (regeneration)
  • A sudden load change
  • A surge on the supply
  • Pr.52 = 12 shows the DC bus peak of the last run; the next start clears it (manual p. 132)
  • Keep the load steady, or use the regeneration avoidance function
  • Add a brake resistor, brake unit or power regeneration common converter (FR-CV) where the load keeps regenerating
E.OV3Regenerative overvoltage trip during deceleration or stopFaultManual p. 262 Regenerated energy pushed the internal DC bus voltage over its limit while slowing down or stopped.
  • Deceleration time too short for the load's inertia
  • Braking too often
  • Pr.52 = 12 shows the DC bus peak of the last run; the next start clears it (manual p. 132)
  • Lengthen the deceleration time to suit the load, or make the braking cycle longer
  • Use regeneration avoidance, or add a brake resistor, brake unit or FR-CV if needed
E.THTInverter overload trip (electronic thermal O/L relay function)FaultManual p. 263 The electronic thermal protection for the inverter's output transistors tripped.
  • Load too heavy for the inverter (150 % for 60 s is its overload rating)
  • Acceleration too short or torque boost set wrong
  • Load pattern setting wrong, or a hot enclosure
  • Reduce the load or lengthen the acceleration / deceleration times
  • Check Pr.0 [Torque boost] and Pr.14 [Load pattern selection]
  • Keep the surrounding air within the rating; a reset clears the thermal count
E.THMMotor overload trip (electronic thermal O/L relay function)FaultManual p. 263 The inverter's electronic thermal protection for the motor tripped.
  • Motor overloaded, or running long at low speed with less cooling
  • Pr.71 [Applied motor] not matching the motor
  • Stall prevention set wrong
  • Reduce the load and let the motor cool; a reset clears the thermal count
  • Check Pr.9 [Electronic thermal O/L relay] against the motor's rated current
  • For a constant-torque motor, set it in Pr.71
E.FINHeatsink overheatFaultManual p. 263 The heatsink temperature sensor tripped the inverter.
  • Surrounding air too hot
  • A clogged heatsink
  • A stopped cooling fan (FN on the panel)
  • Keep the surrounding air within the rating
  • With power locked out and the DC bus confirmed discharged, clean the heatsink
  • With power locked out, replace the cooling fan if it has stopped (see FN)
E.ILFInput phase lossFaultOff in the initial settingManual p. 264, 149 One of the three input phases was lost, or the phases are badly unbalanced (three-phase input models only).
  • A blown fuse or an open breaker pole
  • A broken or loose input cable
  • A badly unbalanced supply
  • With power locked out, check fuses, terminals and the input cables
  • Checking the supply while it runs is live work for a qualified electrician, or use a power-quality recorder
  • Pr.872 [Input phase loss protection selection] = 1 turns this check on; its initial value is 0
E.OLTStall prevention stopFaultManual p. 264 Stall prevention held the output at 1 Hz for 3 s because the load was too heavy.
  • Motor overloaded or the machine jammed
  • Pr.22 [Stall prevention operation level] set too low
  • With power locked out, check that the machine turns freely
  • Reduce the load
  • Check the Pr.22 setting
E.BEBrake transistor alarm detectionFaultManual p. 264 The inverter found a fault in its brake transistor circuit.
  • Large regenerated energy from the motor
  • Braking too often, or the wrong brake resistor
  • The manual says to switch the inverter's power off at once
  • Check the load inertia, how often it brakes and the brake resistor choice
  • Its remedy is replacing the inverter
E.GFOutput side earth (ground) fault overcurrent at startFaultOff in the initial settingManual p. 264, 149 A ground fault on the output side was found when the inverter started.
  • Damaged motor cable insulation
  • A motor winding with a fault to ground
  • Moisture in the motor, the terminal box or the conduit
  • Pr.249 [Earth (ground) fault detection at start] = 1 turns this check on; its initial value is 0
  • A qualified person does any insulation test with power locked out, disconnects the motor leads from U, V, W first and never insulation-tests the inverter itself
  • Fix the grounded part before resetting
E.LFOutput phase lossFaultManual p. 264, 149 One of the output phases (U, V, W) was lost while the inverter was running.
  • An open conductor or a loose terminal to the motor
  • A motor smaller in capacity than the inverter
  • With power locked out and the DC bus confirmed discharged, inspect the motor wiring end to end
  • Use a motor that matches the inverter capacity
  • Pr.251 [Output phase loss protection selection] sets this check; it is on in the initial setting
E.OHTExternal thermal relay operationFaultOff in the initial settingManual p. 265, 116 A thermal relay or motor thermostat wired to the OH input opened.
  • The motor overheating from overload or heavy duty
  • A loose wire on the OH input
  • Reduce the load and how often it runs
  • Find the device wired to the OH input (Pr.178 to Pr.182 = 7) and why it opened
  • The inverter needs a reset even after the relay closes again
E.PTCPTC thermistor operationFaultOff in the initial settingManual p. 265 The motor's PTC thermistor on terminals 2 and 10 went over the Pr.561 resistance level.
  • The motor overheating from overload
  • A loose or broken thermistor connection
  • Pr.561 [PTC thermistor protection level] set wrong
  • Reduce the load
  • With power locked out, check the thermistor wiring to terminals 2 and 10
  • Check Pr.561; its initial value 9999 turns this check off
E.PEParameter storage device fault (control circuit board)FaultManual p. 265 The memory that stores the parameters (EEPROM) has a fault.
  • Too many parameter writes
  • A memory fault on the control board
  • The manual's remedy is contacting your Mitsubishi sales representative
  • For frequent writes over communication, Pr.342 = 1 writes to RAM only (lost at power-off)
E.PUEPU disconnectionFaultManual p. 265, 161 Communication with the parameter unit, or RS-485 on the PU connector, was lost.
  • A loose or broken parameter unit cable
  • Communication retries or the check time interval exceeded
  • Reconnect the parameter unit cable
  • Check the communication data and settings, and Pr.122 [PU communication check time interval]
  • Pr.75 sets the cable check; its initial value 14 leaves it off
E.RETRetry count excessFaultOff in the initial settingManual p. 265, 147 The retry function could not restart the inverter within the set number of tries.
  • The fault behind the retries is still there
  • Retry restarts the motor on its own: remove the start signal before working on the machine
  • Find and fix the fault that came before this one
  • Never raise the retry count (Pr.67, initial value 0) to ride over a fault
E.CPU / E.5CPU faultFaultManual p. 266 A communication fault of the inverter's built-in CPU.
  • Electrical noise from devices near the inverter
  • An internal fault
  • Deal with noise sources near the inverter
  • If it stays, the manual's remedy is contacting your Mitsubishi sales representative
E.CDOOutput current detection value exceededFaultOff in the initial settingManual p. 266, 127 Output current went over the Pr.150 detection level and Pr.167 is set to trip.
  • A heavier load than the detection level allows
  • Detection settings too tight for the machine
  • Check Pr.150, Pr.151, Pr.166 and Pr.167
  • Pr.167 = 1 makes this a trip; its initial value 0 doesn't
E.IOHInrush current limit circuit faultFaultManual p. 266 The resistor in the inrush current limit circuit overheated.
  • Power switched on and off too often
  • Use a circuit that doesn't cycle the power often
  • If it stays, the manual's remedy is contacting your Mitsubishi sales representative
E.AIEAnalog input faultFaultManual p. 266 Terminal 4 got a signal while Pr.267 and the voltage / current input switch were set differently.
  • Pr.267 [Terminal 4 input selection] and the input switch don't match
  • A voltage signal wired to an input set for current, or the reverse
  • Set Pr.267 and the switch to match the signal
  • Or give the frequency command as a current
E.SAFSafety circuit faultFaultManual p. 266 The safety circuit is malfunctioning, or the S1–SC or S2–SC safety stop line opened.
  • A safety device (relay module, door switch, e-stop) opened the circuit
  • A broken or loose wire on S1, S2 or SC
  • Never jumper S1 or S2 to SC on a machine that uses the safety stop function
  • Check the safety relay module and the S1 / S2 / SC wiring
  • Mitsubishi's safety stop function manual (BCN-A211508-000) has the causes
OLStall prevention (overcurrent)WarningManual p. 259 Overcurrent stall prevention is working: the inverter holds back the frequency to limit the current.
  • Load too heavy, or acceleration / deceleration too fast
  • Torque boost or starting frequency too high
  • Lengthen Pr.7 and Pr.8 [Acceleration / Deceleration time]
  • Reduce the load; change Pr.0 [Torque boost] in 1 % steps
  • Check Pr.22 [Stall prevention operation level] (initial value 150 %)
UVUndervoltageWarningStops the outputManual p. 260 Supply voltage dropped below about 115 V AC (200 V class) or 230 V AC (400 V class); the output stops until it recovers.
  • A low or dipping supply (about 58 V AC is the level on 100 V class models)
  • A lost phase or a loose supply connection
  • Read the DC bus on the panel first: Pr.52 = 8 shows the converter output voltage (manual p. 132)
  • Checking the supply while it runs is live work for a qualified electrician, or use a power-quality recorder
  • Look at the devices on the supply line; UV clears once the voltage is back to normal
THElectronic thermal relay function pre-alarmWarningManual p. 260 The electronic thermal value reached 85 % of the Pr.9 setting; at 100 % the inverter trips.
  • A heavy load or sudden acceleration
  • Pr.9 [Electronic thermal O/L relay] set wrong
  • Reduce the load and how often it runs
  • Check Pr.9 against the motor
RBRegenerative brake pre-alarmWarningManual p. 260 The regenerative brake duty reached 85 % of the Pr.70 setting; at 100 % an E.OV trip follows.
  • Braking too often or too hard
  • Pr.30 / Pr.70 not set for the brake resistor fitted
  • Lengthen the deceleration time
  • Check Pr.30 [Regenerative function selection] and Pr.70 [Special regenerative brake duty]
PSPU stopWarningManual p. 260, 161 STOP/RESET on the operation panel was pressed while the inverter ran from another command source.
  • Someone pressed STOP/RESET at the panel
  • Turn the start signal off, then release with the PU/EXT key
  • Pr.75 sets where the panel's stop key works
SASafety stopWarningOutput held offManual p. 261 The safety stop function is active and holds the output off.
  • A safety device opened S1 / S2
  • A broken wire on S1, S2 or SC
  • Find which safety device opened and why before restarting
  • Never jumper S1 or S2 to get a machine running
  • If SA stays with both inputs closed, the manual points to an internal failure
FNFan alarmAlarmManual p. 261 The cooling fan stopped, or isn't running the way Pr.244 [Cooling fan operation selection] sets it.
  • A worn or blocked fan
  • With power locked out, check the fan for blockage
  • For a failed fan, the manual says to contact your Mitsubishi sales representative

The name is the manual's own name for the code; the code is what the operation panel shows. The manual files UV and SA under warnings, but both hold the output off; the other warnings and the FN alarm don't trip the inverter. Other error messages and warnings in the same list that this page doesn't cover: oL, MT, HOLD, LOCD, Er1–Er4, Err., E--- – see the manual for those.

Source: Mitsubishi Electric, FR-D700 Instruction Manual (Applied), FR-D720-0.1K to 15K, FR-D740-0.4K to 15K, FR-D720S-0.1K to 2.2K, FR-D710W-0.1K to 0.75K, IB(NA)-0600366ENG-H (June 2018) – chapter 5, Troubleshooting (pages 255 to 266), with the parameter and maintenance pages named in each row – page numbers on this page are the manual's printed page numbers, read on October 17, 2026.

Meanings, causes and checks are summarized in our own words. The manual is the reference: it has every code, the full corrective actions and the safety instructions. A newer revision of the manual may add codes, so check the current revision for your drive.

FR-D700 inverters in stock

Mitsubishi FR-D700 (FR-D720, FR-D740, FR-D720S) part numbers on our shelves right now. Every item is photographed, so check the nameplate – catalog number and series – against the drive you're replacing.

  • FR-D740-160-NAMitsubishi Electric FR-D740-160-NA 23.8A 3PH AC380-480V50/60Hz
  • FR-D740-080-NAMitsubishi FR-D740-080-NA D700 VFD Inverter Drive 3 Phase 480V 3HP 2.2kW 8.0A
  • FR-D740-120-NAMitsubishi FR-D740-120-NA 16.7A 3PH AC380-480V
  • FR-D740-1Mitsubishi FR-D740-1. 5K AC380-480V 50/60Hz
  • FR-D740-1.5KMitsubishi FR-D740-1.5K FREQROL D700 VFD Inverter 1.5kW 2HP 400V 3 Phase Drive
  • FR-D720S-042-NAMitsubishi FR-D720S-042-NA Compact Inverter D700 VFD 0.75kW 1HP 200-240V 1PH
  • FR-D740-050-NAMitsubishi FR-D740-050-NA D700
  • FR-D740-5.5KMitsubishi Electric FR-D740-5.5K FR-D740-5.5K 50/60Hz

Fault won't clear?

When the checks point to the drive itself – the manual's “replace the inverter” or “contact your sales representative” – send us the fault code and the catalog number from the nameplate. We check our shelves and our sourcing network and reply with a written quote. Purchase orders are welcome; payment is due before we ship.

Frequently asked questions

How do I reset a fault on a Mitsubishi FR-D700?

Fix the cause first and turn the start signal off – resetting with the start signal still on starts the motor without warning. Then press STOP/RESET on the operation panel, turn on the RES signal for more than 0.1 s, or switch the power off and on again after the panel goes dark. A reset also clears the electronic thermal count and the retry count.

What does UV mean on a Mitsubishi FR-D700?

UV is undervoltage: the supply dropped below about 115 V AC on a 200 V class inverter (about 230 V AC on a 400 V class). The manual lists it as a warning, but the inverter stops its output until the voltage is back to normal. Read the DC bus on the panel with Pr.52 = 8, and leave checks of the live supply to a qualified electrician.

What is the difference between a fault, a warning and an alarm on an FR-D700?

A fault (E. and a code) shuts the inverter's output off and sends the fault signal until it is reset. Warnings (OL, TH, RB, PS ...) and the FN fan alarm leave the output on, though an ignored warning can turn into a fault; UV and SA are the exceptions that hold the output off.

Where can I see which faults an FR-D700 had?

In the operation panel's fault history: the last eight faults, each with the output frequency, current, voltage and energization time when it happened. Er.CL clears the history. We have separate pages for the FR-E700 and FR-E800.

Can you supply a replacement FR-D700 inverter?

Send the model from the rating plate (for example FR-D740-...) and the fault code through our quote form. We check our shelves and our sourcing network and reply with a written quote.

Send us the fault code

Tell us the code and the drive's catalog number – we'll check our shelves and our sourcing network for a replacement and quote it in writing.

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