The electric motor's own bearings are failing. Similar symptoms to airend bearing failure but the noise comes from the motor end.

What you'll see

Grinding or whining noise from the motor. Increased vibration at the motor end. The motor may feel hotter than normal. If the drive-end bearing fails repeatedly, check alignment between motor and airend: misalignment destroys motor bearings.
Before you assume this is the problem

Use a stethoscope to confirm the noise is from the motor, not the airend or coupling.

See all causes of unusual noise →

How to diagnose

  1. Isolate to the motor

    Place a stethoscope or screwdriver on the motor body. Compare the noise level with the airend body. If it's clearly louder at the motor, the motor bearings are the problem.

    Result: Noise at motor = motor bearings.

  2. Check for repeated failures

    If the drive-end bearing keeps failing, check motor-to-element alignment. Misalignment puts side load on the bearing that it's not designed for. Also check if the motor is unbalanced.

    Result: Repeated failure = alignment or motor balance issue.

How to fix it

  1. Replace motor bearings

    Have the motor bearings replaced by a motor shop. If the bearing failure repeats, send the motor for a complete overhaul including balance check and alignment verification.

Common mistakes

Don't keep replacing bearings without checking alignment. Misalignment is the number one cause of repeated motor bearing failure on direct-drive compressors.

Parts & tools

Motor bearing replacement (motor shop work). Alignment tools.

Review safety precautions before starting →

This issue can also cause

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