What does Yaskawa A1000 LF Fault - Causes & Fix mean?

LF means output phase loss: the drive detects missing or unbalanced motor output phases. Check output wiring and terminals first.

How do I fix Yaskawa A1000 LF Fault - Causes & Fix?

Work through the step-by-step fix below. Start with the quick reset and the most common cause, then check the specific part this guide points to. Most fixes need only basic hand tools and the right replacement part.

Can I keep using my Yaskawa appliance with A1000 showing?

Usually not. Yaskawa appliances show this error when a part or safety circuit is out of range, so running it can stop the cycle or make the problem worse. Diagnose and clear the error before normal use.

What part is most commonly replaced for Yaskawa A1000 LF Fault - Causes & Fix?

The parts that most often fix Yaskawa A1000 LF Fault - Causes & Fix are listed in the parts section of this guide. Match the part to your exact model and serial number before you buy.

Is Yaskawa A1000 LF Fault - Causes & Fix a DIY repair or do I need a technician?

Many fixes are DIY-friendly with basic tools, such as door switches, drain pumps, water inlet valves, thermostats, heating elements, and filters. Sealed-system, refrigerant, gas, or high-voltage work should go to a licensed technician for safety.

Yaskawa A1000 LF Fault - Causes & Fix

Yaskawa A1000 LF Fault — What It Means

The LF fault on a Yaskawa A1000 variable frequency drive stands for Output Phase Loss. The drive has detected that one or more of the three motor output phases is missing or significantly out of balance. This is an output-side problem, not an input power issue. The drive monitors current flowing to the motor and trips LF when it sees loss of current on one or more phases.

Parameter L8-07 controls this detection. When L8-07 is set to 1 or 2, phase-loss detection is enabled and the drive will trip on LF if it sees an output phase problem. The fault protects both the drive and the motor from running in an unsafe unbalanced condition that can overheat windings or damage output transistors.

Before You Replace Anything

Technicians sometimes replace the drive power board when the real problem is a loose output terminal or damaged motor cable. Always inspect and measure the motor wiring and motor windings before replacing drive hardware.

Jump to Fix

Common Causes

Loose or disconnected output terminals (~35%) Output terminal screws at the drive or motor junction box are loose, corroded, or not tightened to the manufacturer’s specified torque, causing intermittent or missing phase connection.
Damaged motor cable or wiring (~25%) The cable between the drive and motor has a broken conductor, damaged insulation, burn marks, or an open connection inside the cable run.
Failed or damaged motor windings (~20%) One or more motor windings are open, shorted, or severely imbalanced due to insulation failure, overheating, or mechanical damage inside the motor.
Motor undersized for the drive (~10%) The motor’s rated full-load current is less than about 5% of the drive’s rated output current, causing the drive to see insufficient current and flag a phase loss.
Failed output transistor or power stage in the drive (~10%) An output IGBT or transistor module inside the drive has failed and is no longer switching one phase, though this is less common than wiring and motor problems.

Quick Diagnosis

Answer these to narrow it down fast.

Are all three motor output cables visibly connected and terminals tight at both the drive and motor?

Yes: Wiring connections are likely intact. Proceed to measure motor winding resistance to check for an open or damaged winding.
No: You have found a loose or missing connection. Re-land and torque all output terminals to specification and retest the drive.

With power off and motor disconnected, do all three motor windings measure similar low resistance (typically a few ohms) with no open circuits?

Yes: Motor windings are balanced and intact. The problem is likely in the cable, connections, or the drive output stage itself.
No: One winding is open or severely out of balance. The motor is faulty and must be repaired or replaced.

Is the motor's nameplate full-load current rating at least 5% of the drive's rated output current?

Yes: Motor sizing is acceptable. Focus diagnostics on wiring integrity and drive output hardware.
No: The motor is too small for the drive and may trigger phase-loss detection even when wired correctly. Consult the drive manual or resize the motor/drive pairing.

Step-by-Step Fix

Lock out and tag out the drive and verify zero voltage at the input and output terminals with a multimeter before beginning any inspection or testing.
Inspect all output wiring from the drive output terminals to the motor junction box for visible damage, burn marks, broken strands, or damaged insulation.
Check terminal tightness at both the drive output terminal block and the motor junction box using a torque wrench and the tightening torque values listed in the A1000 installation manual for your frame size.
Measure motor winding resistance with the motor disconnected from the drive: use an ohmmeter to measure phase-to-phase resistance (U-V, V-W, W-U) and confirm all three readings are present, low (typically a few ohms), and within a few percent of each other.
Verify drive-to-motor sizing by comparing the motor nameplate full-load current to the drive rated current: if the motor current is less than 5% of the drive rating, the drive may false-trip on phase loss and you should adjust L8-07 or resize the equipment.
Check parameter L8-07 in the drive using the keypad or programming software to confirm phase-loss detection is set as intended (1 or 2 enables detection, 0 disables it).
Isolate the motor and test the drive by disconnecting the motor leads and running the drive into a known-good motor or test load: if the LF fault persists with good wiring and a good motor, suspect a failed output transistor or power stage and consult a drive service center or replace the drive power board.

Parts Often Needed

Part	Notes
Motor output cable (3-conductor shielded VFD-rated)	Amazon \| Use cable rated for VFD applications with proper shielding and sized per NEC and drive manual for your motor horsepower and cable length.
Yaskawa A1000 output power board or IGBT module	Amazon \| Frame-specific replacement part available from Yaskawa or authorized service centers; confirm part number from your drive nameplate before ordering.

When to Call a Pro

Call a qualified electrician or VFD technician if you are not trained in industrial electrical work, if you cannot safely lock out and verify de-energized high-voltage terminals, or if the motor and wiring test good but the fault remains. Diagnosing and replacing internal drive components such as output transistors or power boards requires specialized knowledge, proper ESD precautions, and access to service documentation. A professional can also perform insulation testing (megohm testing) on the motor and cable, interpret parameter settings, and confirm proper drive-to-motor sizing per NEC and manufacturer guidelines.

Rough cost: A pro service call runs about $150-500.