What Are the Common Failures of Encoders?
In elevator and escalator control systems, the encoder is an important electronic component used for speed detection, position feedback, and synchronous control. It functions like the “sensor of the elevator’s brain,” responsible for telling the main control system “at what speed and in which direction the elevator is running, and where it has reached.” Once the encoder malfunctions, the elevator or escalator will immediately enter an abnormal state, and may even become unable to operate.
Today, the technical team from A-FLY Elevator & Escalator Parts Supplier will summarize the most common encoder failure types and how to determine whether replacement is needed.
1. Common Failure 1: No Signal Output / Signal Loss
This is the most common encoder failure and often the cause of shutdowns. Symptoms include:
- Elevator cannot start
- Escalator enters locked state
- Main board displays “encoder no feedback”
Possible causes:
- Encoder power failure
- Signal cable disconnection or poor contact
- Internal sensor chip failure in the encoder
This type of failure typically requires direct encoder replacement or cable repair.
2. Common Failure 2: Unstable Signal / Intermittent Pulse Loss
If the elevator runs irregularly—sometimes fast, sometimes slow—or if the escalator shows intermittent vibration, the encoder signal may be unstable.
Common symptoms:
- Speed fluctuations
- Frequent false alarms
- Slight vibration during elevator operation
Common causes include:
- Encoder bearing wear
- Magnet deterioration
- Off-center installation
- Vibration-induced signal jitter
Encoders are precision components, and once stability drops, they can no longer be used long-term.
3. Common Failure 3: Incorrect Direction Recognition
When the encoder misidentifies direction, the elevator may show:
- “Up becomes down” direction errors
- Escalator unable to switch direction
- Main controller reports “direction error”
Common causes:
- A/B phase signal sequence error
- Incorrect wiring
- Encoder direction settings modified
Direction errors will trigger system protection and must be checked immediately.
4. Common Failure 4: Resolution Distortion / Pulse Count Deviation
When encoder resolution decreases, the main control system cannot obtain accurate speed or position information.
Symptoms include:
- Speed change points occurring too early or too late
- Inaccurate floor leveling
- Unstable escalator speed
Possible causes:
- Contamination on the encoder disc (oil, water, dust)
- Aging of optical sensor
- Magnetic encoder magnet weakening
This is a typical aging problem and often requires encoder replacement.
5. Common Failure 5: Mechanical Damage (Shaft Breakage / Housing Cracks)
Encoders exposed to long-term vibration may experience:
- Encoder shaft breakage
- Bearing seizure
- Housing damage
- Loosened mounting bracket
These physical damages cause complete signal failure and are severe, non-repairable failures.
6. Common Failure 6: Environment-Related Damage
Many encoder failures are not due to quality issues but environmental factors such as:
- Hoistway humidity causing internal short circuits
- Escalator pit water accumulation causing corrosion
- High temperature leading to chip failure
- Oil contamination preventing correct optical recognition
Such problems are more likely to occur in metro stations, basements, and shopping malls.
7. How to Determine Whether the Encoder Should Be Replaced?
Generally, if any of the following occurs, replacement is recommended:
- Long-term unstable encoder signal
- Frequent direction error alarms
- Obvious looseness or abnormal noise from the encoder shaft
- Elevator leveling deviation beyond allowed range
- Frequent “Encoder Fault / SPD Error” on main controller
- Encoder exceeding service life (5–8 years)
Encoders are precision positioning components directly related to safe operation. Once problems occur, they are not very repairable and often require replacement.
8. A-FLY — Providing Full-Series Encoder Solutions for Elevators and Escalators
As a leading elevator & escalator parts supplier, A-FLY provides high-quality encoders compatible with multiple brands, including:
- Elevator machine encoders
- Escalator drive encoders
- Magnetic encoders
- Photoelectric encoders
- Replacement encoders for traction units
- Encoder retrofit kits for machine upgrades
Compatible with major mainstream elevator and escalator systems.
A-FLY encoders feature:
- High-precision pulse output
- Anti-vibration design
- Enhanced protection for high-temperature and humid environments
- Long-life bearings
- International standard wiring compatibility
Whether for maintenance replacement, modernization, or machine upgrades, A-FLY provides reliable and highly stable encoder solutions.
9. Summary: The Encoder May Be Small, But It Affects the Entire Elevator’s Safety
Encoder issues are often not immediately obvious, yet they play a decisive role in speed control, position detection, and operational smoothness. Regular inspection and timely replacement are essential tasks in maintenance.
Choose A-FLY to make your elevators and escalators operate more accurately, more stably, and more safely.
