Yaskawa Alarm Codes Explained: Complete Guide & Troubleshooting (2026)

Most Common Yaskawa Errors

Instead of guessing, you can jump directly into detailed solutions based on real-world issues:

• Pendant communication faults → see how to fix Yaskawa pendant communication errors
• Power-related shutdowns → diagnose Yaskawa A.750 power supply alarms
• Load-related stops → troubleshoot Yaskawa A.720 overload alarms
• Control instability → identify Yaskawa control board failures

Related guide: Yaskawa A.750 Alarm Codes

Overview

Yaskawa servo systems continuously monitor electrical signals, motion accuracy, and load conditions. When abnormal behavior is detected, the system generates alarm codes to protect the servo drive, motor, and mechanical components from damage.

This page serves as a central troubleshooting hub to help you:

• Quickly identify Yaskawa alarm codes
• Understand real-world causes beyond manual definitions
• Follow a structured diagnostic process
• Determine whether to repair or replace components

Whether you're dealing with an A.710 overcurrent alarm or a persistent encoder fault, this guide helps you move from symptom → root cause → solution.

How to Read Yaskawa Alarm Codes

• A.xxx → Servo, motion, or electrical alarms
• CPF / Communication → Network or control issues
• Encoder-related → Feedback signal problems

Quick Diagnosis Logic:

• Electrical → Check power supply and servo drive
• Mechanical → Check load and gearbox
• Feedback → Check encoder and cables

1. Electrical & Power Alarms

Electrical alarms are commonly associated with the servo drive power stage, although external components should always be checked first.

🔌 A.710 Overcurrent Alarm

The Yaskawa A.710 overcurrent alarm occurs when current spikes exceed safe limits, often during sudden stops or collisions.

Common causes include:

• Motor winding short circuits
• Grounding or power issues
• Internal IGBT degradation inside the drive

For detailed diagnosis, see the Yaskawa A.710 overcurrent troubleshooting guide .

A.750 Power Supply Error

The Yaskawa A.750 power supply error indicates unstable or abnormal input power conditions.

If external voltage instability is ruled out, the issue often points to internal drive circuitry degradation.

A.820 Regenerative Error

Common causes include:

• Incorrect regenerative resistor configuration
• Excessive deceleration settings
• Servo drive regenerative circuit limitations

See the Yaskawa A.820 regenerative error troubleshooting guide .

A.840 Overvoltage Error

The Yaskawa A.840 overvoltage alarm is commonly triggered during high-speed deceleration.

Typical causes include:

• DC bus sensing instability
• Internal servo drive power circuit degradation

2. Mechanical Load & Motion Alarms

Unlike electrical faults, these alarms are usually caused by external mechanical conditions rather than internal electronics.

A.720 Overload Alarm

The Yaskawa A.720 overload alarm indicates that the motor is operating beyond its continuous torque capacity.

Typical causes include:

• Gearbox wear or misalignment
• Increased friction or binding
• Long-term heavy-load operation

A.850 Position Error

The Yaskawa A.850 position error occurs when the system cannot accurately reach the commanded position.

• Mechanical backlash
• Encoder feedback inconsistency
• Parameter mismatch

A.860 Following Error

The Yaskawa A.860 following error indicates that actual motion cannot keep up with commanded motion.

• Load mismatch
• Servo tuning issues
• Feedback instability

3. Feedback & Encoder Alarms

These alarms affect signal integrity and synchronization, making them critical for motion accuracy.

A.810 Encoder Error

The Yaskawa A.810 encoder error is commonly caused by encoder cable degradation rather than encoder failure.

Typical cable-related issues include:

• Repeated cable bending
• Shielding failure
• Internal wire fatigue

A.830 Encoder Communication Error

The Yaskawa A.830 encoder communication error occurs when encoder signals cannot be transmitted reliably.

• Servo drive communication circuit failure
• Internal PCB instability

Communication Errors (CPF / A.C90)

These errors indicate communication instability between the controller and servo drive.

• Internal PCB degradation
• Control board instability
• Connector oxidation or signal loss

4. Thermal Protection Alarms

A.790 Overheat Alarm

The Yaskawa A.790 overheat alarm occurs when system temperature exceeds safe operating limits.

• Poor ventilation
• Cooling fan degradation
• High ambient temperature

A.7A0 Heat Sink Overheat

The Yaskawa A.7A0 heat sink overheat indicates excessive internal heat accumulation inside the drive.

• Restricted airflow
• Dust contamination
• Long-duration heavy-load operation

5. Quick Diagnosis Guide (By Symptom)

If you do not know the exact alarm code, match your symptom:

Symptom	Likely Alarm
Robot stops instantly	A.710 / A.750
Cannot handle load	A.720
Position inaccurate	A.850
Motion lag	A.860
Encoder signal unstable	A.810 / A.830
Speed instability	A.840
Overheating shutdown	A.790
Stops during deceleration	A.820

6. Why Yaskawa Alarms Appear

In practical applications, alarms are commonly triggered by:

• Mechanical resistance increase
• Cable wear in dynamic applications
• Servo drive internal degradation
• Power instability
• Improper motion parameters

Key Insight

When multiple alarms appear together, they often originate from one underlying failure point rather than multiple unrelated problems.

• Servo drive failure
• Encoder or power cable degradation
• Mechanical overload cascade

7. 5-Minute Troubleshooting Strategy

Step 1 – Identify the category

• Electrical
• Mechanical
• Feedback / encoder related

Step 2 – Isolate external components

• Motor
• Encoder cable
• Mechanical load

If the alarm remains after isolation, the fault is likely inside the servo drive.

Step 3 – Observe when the alarm occurs

Scenario	Likely Cause
At startup	Electrical or drive issue
During motion	Load or feedback issue

Step 4 – Verify external conditions

• Power supply stability
• Cable integrity
• Mechanical resistance

🔧 Field Pattern

• Intermittent alarms → usually cable-related
• Persistent alarms without load → drive failure is highly likely

8. Recommended Yaskawa Spare Parts

Most Yaskawa robot alarms can be traced back to a few critical components.

Servo Drives

• Electrical alarms persist
• Multiple alarm types appear simultaneously
• Motion instability

Typical failures include:

• Internal circuit degradation
• IGBT damage
• DC bus instability

Servo Motors

• Overload alarms
• Overheating
• Abnormal torque behavior

Common motor failures include:

• Bearing wear
• Insulation breakdown
• Winding damage

Cables (Most Frequently Replaced)

Cable failures are one of the most overlooked causes of intermittent alarms.

• Encoder signal loss
• Communication instability
• Random alarm resets

Replacing encoder or signal cables often resolves intermittent faults quickly.

Decision Tip: If multiple unrelated alarms continue after isolation testing, replacing the servo drive resolves the issue in most cases.

Related Troubleshooting Guides

• How to fix Yaskawa pendant communication errors
• Yaskawa A.750 power supply alarm troubleshooting
• Yaskawa control board failure diagnosis guide
• Yaskawa A.720 overload alarm repair guide

9. Repair vs Replacement

Repair

• Lower initial cost
• Higher uncertainty
• Risk of repeated faults

Replacement

• Faster recovery
• Stable long-term performance
• Lower production risk

Practical rule: If alarms persist after isolation testing, replacing the servo drive is usually more reliable than repeated repair attempts.

FAQ

What is the most common Yaskawa alarm code?

• A.710 Overcurrent
• A.720 Overload

Can one alarm have multiple causes?

Yes — alarm codes indicate symptoms, not exact failure points.

Why do multiple alarms appear together?

Multiple alarms often originate from a single failing component, especially:

• Servo drives
• Encoder cables
• Power cables

Can alarms be ignored if they reset?

No — even temporary alarms indicate abnormal system stress.

What is the fastest way to fix recurring alarms?

Use a structured process: Isolate → identify → replace the faulty component.