When a dosing pump motor fails to start, it can disrupt the entire chemical dosing process, leading to inaccurate chemical injection or system downtime. Understanding the possible reasons behind a dosing pump motor not working helps ensure timely maintenance and reliable operation. This article explores the most common electrical, mechanical, and control-related causes and offers effective troubleshooting methods.

🔌 1. Electrical Causes

1.1 Power Supply Failure or Voltage Issues

Possible Causes:

• Power switch not turned on

• Blown fuse or tripped circuit breaker

• Loose wiring or open circuit

• Low voltage or phase loss

Troubleshooting:

• Use a multimeter to check the voltage at the power input.

• Inspect for blown fuses, loose terminals, or missing phases.

• Verify that contactors and circuit breakers are working correctly.

1.2 Motor Burnout or Short Circuit

Possible Causes:

• Continuous overload operation

• Moisture or chemical ingress leading to insulation failure

Troubleshooting:

• Measure the insulation resistance (should be above 0.5 MΩ).

• Check for unusual smell, heat, or smoke from the motor.

• If necessary, disassemble the motor and inspect the windings.

1.3 Control Circuit Fault

Possible Causes:

• Loose control wiring

• Faulty start/stop button or relay failure

Troubleshooting:

• Tighten all control wiring connections.

• Test the start/stop switch and relay operation.

• Replace defective components if needed.

1.4 Overload or Thermal Protection Activated

Possible Causes:

• Excessive current draw due to mechanical blockage

• Overload relay tripped

Troubleshooting:

• Check and reset the thermal overload relay.

• Verify that the pump is not jammed before restarting.

⚙️ 2. Mechanical Causes

2.1 Pump Head or Drive Assembly Jammed

Possible Causes:

• Chemical crystallization inside the dosing head

• Foreign particles blocking valves or diaphragms

• Plunger stuck due to lack of lubrication

Troubleshooting:

• Disconnect power and manually rotate the motor fan to test for free movement.

• If stiff or stuck, remove the pump head and clean all components thoroughly.

2.2 Coupling Misalignment or Damage

Possible Causes:

• Loose or misaligned coupling between the motor and pump head

Troubleshooting:

• Inspect the coupling for loosened bolts or wear.

• Align the motor and pump shafts correctly.

2.3 Bearing Failure or Poor Lubrication

Possible Causes:

• Lack of lubrication or contaminated grease

• Bearing wear due to extended operation

Troubleshooting:

• Check for unusual noise or vibration.

• Replace damaged bearings and add fresh lubricant.

🧠 3. Control and System Causes

3.1 Frequency Converter or Controller Failure

Possible Causes:

• Inverter alarm or protection mode triggered

• Internal circuit fault

Troubleshooting:

• Check the inverter display for alarm codes.

• Refer to the user manual to reset or replace faulty parts.

3.2 PLC or Automation Signal Failure

Possible Causes:

• No start signal in automatic mode

• PLC output or relay malfunction

Troubleshooting:

• Switch to manual mode and test if the pump runs.

• Check PLC output terminals and relay conditions.

✅ 4. Summary: Quick Diagnosis Guide

💡 Maintenance Tips to Prevent Motor Failure

• Regularly clean and inspect the pump head and valves to prevent chemical buildup.

• Ensure proper ventilation and avoid continuous overload operation.

• Test the insulation resistance of the motor quarterly.

• Keep all control wiring dry and properly tightened.

• Schedule preventive maintenance based on dosing frequency and chemical type.