Squealing, slipping, or flapping belts. Common on belt-driven compressors: the belt may be worn, loose, misaligned, or the wrong type.

What you'll see

A squealing or chirping noise, especially during startup or when load changes. The belt may be visually worn, cracked, glazed, or loose. In severe cases, the belt slips under load, the motor spins but the element doesn't reach full speed, causing reduced output.
Before you assume this is the problem

See all causes of unusual noise →

How to diagnose

  1. Visual inspection

    Stop the machine, remove the belt guard, and inspect the belt. Look for cracks, glazing (shiny hard surface), fraying, or chunks missing. Check tension: the belt should deflect about 10-15mm under moderate thumb pressure at the midpoint.

    Result: Worn, cracked, or loose belt = replace.

  2. Check pulley alignment

    Use a straight edge across the pulleys. They should be perfectly aligned. Misalignment causes uneven belt wear and noise.

    Result: Misaligned pulleys = realign.

How to fix it

  1. Replace the belt and check alignment

    Install a new belt of the correct type and size. Tension it per manufacturer spec. Verify pulley alignment. If pulleys are worn (groove damage), replace them too.

Common mistakes

Don't overtighten belts. Excessive tension wears motor and element bearings prematurely. Follow the manufacturer's tension specification.

Parts & tools

Replacement belt (correct type and size). Straight edge for alignment check. Tension gauge if available.

Review safety precautions before starting →

Safety

Never work near a running belt drive without guards in place. Shut down and disconnect power before inspecting belts.