How to Check a Faulty Forklift Motor (DC & AC Motors)

How to Check If a Forklift Motor Is Faulty – Accurate & Practical Guide

The motor is the core component of an electric forklift. When the motor fails, the forklift may run weakly, overheat quickly, or even stop working although the battery is still charged.

This article provides a step-by-step guide to checking a faulty forklift motor, suitable for both DC motors and AC (3-phase) motors, commonly used in electric forklifts.

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Signs of a Faulty Forklift Motor

A forklift motor usually does not fail suddenly. Common warning signs include:

• Forklift runs weakly, even with light loads

• Motor overheats quickly and smells burnt

• Forklift moves jerkily or vibrates abnormally

• Unusual noise such as humming, screeching, or knocking

• Forklift does not move although the battery has power

• Controller reports motor-related error codes (AC forklifts)

👉 If 2–3 signs appear, inspect the motor immediately.

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How to Check a Forklift Motor Without Disassembly

1. Visual inspection

• Motor housing turns blue or black → overheating

• Power cables are burnt, cracked, or brittle

• Heavy carbon dust or oil contamination

2. Listen to motor noise

• Smooth and steady → normal

• Loud humming → worn bearings

• Knocking sounds → bearing damage or rotor misalignment

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Checking a Forklift Motor Using a Multimeter

1. Measure motor winding resistance

DC forklift motor:

• Measure between two carbon brushes

• Stable low resistance → normal

• 0 ohms → short circuit

• OL / infinite → open winding

AC (3-phase) motor:

• Measure U–V, V–W, U–W

• Similar readings → motor OK

• Large difference → damaged winding

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2. Insulation (ground) test

• One probe on motor housing

• One probe on winding

✅ No reading → good insulation
❌ Resistance detected → motor grounded (rewind or replace)

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Mechanical Inspection of the Motor

1. Motor shaft

• Rotates smoothly → normal

• Hard to rotate or stuck → bearing failure

2. Bearings

• Shaft play

• Grinding noise
  👉 Worn bearings can cause overheating and winding burn

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Motor Fault or Controller Fault – How to Tell?

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When Should You Repair or Replace a Forklift Motor?

Repair if:

• Light winding burn

• Worn bearings

• Worn carbon brushes

Replace if:

• Windings completely burnt

• Rotor deformed

• Severe grounding damage

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Conclusion

Checking a forklift motor is not complicated. The most important steps are:

• Measure winding resistance

• Check insulation to ground

• Monitor heat and noise

Early inspection helps reduce repair costs and avoid controller damage.

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Frequently Asked Questions (FAQ)

Q: The forklift has power but does not move. Is the motor faulty?
A: Possibly. Check whether voltage reaches the motor. If voltage is present but the motor doesn’t rotate, the motor is likely faulty.

Q: Is it dangerous if the forklift motor overheats quickly?
A: Yes. Overheating may cause winding failure and damage the controller.

Q: Are DC and AC forklift motors checked differently?
A: The measuring points differ, but the inspection principles are similar.

Q: Can a faulty forklift motor be rewound?
A: Yes, if the damage is not severe and the rotor is intact.

Q: How often should forklift motors be inspected?
A: Every 6 months, or immediately when abnormal symptoms appear.