Loud Noises in Millwood, WA

AC systems make noise for mechanical, electrical, and refrigerant-related reasons. Here's what's actually happening inside the system when each sound appears.

Banging or Clanking

This is almost always a physical impact - something loose or broken hitting another component. Common sources include a loose blower wheel (the fan that moves air through your ducts), a broken connecting rod inside the compressor, or a detached mounting bracket.

Millwood context: Many homes near the Millwood Historic District and along the Argonne Road corridor were built during the construction booms of the late 1990s and early 2000s. Builder-grade AC units installed 15–20 years ago are now at or past their expected service life. Worn fasteners, degraded vibration dampeners, and fatigued metal components are common in systems of this age - and they tend to announce themselves loudly.

Millwood's climate accelerates this wear. Summer temperatures in the Spokane area regularly climb into the 90s and occasionally past 100°F, pushing AC systems to run long, hard cycles for weeks at a stretch. That sustained heat stress strains fasteners and metal components that are already 15–20 years old. Then, when temperatures drop sharply in fall and winter, the repeated expansion and contraction of those same components loosens what the summer heat weakened. By the time a unit starts banging or rattling, the climate has often been working against it for years.

Rattling

Rattling is usually one of three things: debris (leaves, sticks, or small objects) inside the outdoor condenser unit, a loose panel or access cover, or a failing motor bearing that hasn't fully seized yet. Debris rattling in the condenser is the least serious. A bearing starting to fail is a countdown.

Squealing or Screeching

On older systems with belt-driven blowers, a worn or slipping belt produces a high-pitched squeal. On direct-drive systems (most units built in the last 15 years), squealing points to a motor bearing that's running dry or beginning to fail. Either way, this sound gets worse quickly.

Grinding

Grinding means metal contact that shouldn't be happening. The most common sources are a blower motor bearing that has lost its lubrication, or debris caught between the fan blade and housing. Left alone, grinding leads to motor failure.

Hissing or Bubbling

A steady hiss near the refrigerant lines or indoor air handler often indicates a refrigerant leak. Refrigerant moves through a closed loop under pressure. When that loop develops a crack or a loose fitting, refrigerant escapes - and the system loses its ability to transfer heat efficiently.

Bubbling or gurgling sounds in the refrigerant lines can indicate air or moisture in the system, which also points to a leak that has allowed contamination.

Clicking (Repeated or Continuous)

A single click when the system starts and stops is normal - that's the contactor (an electrical switch) engaging. Rapid, repeated clicking during startup usually means the capacitor is failing. The capacitor gives the compressor and fan motors the electrical jolt they need to start. A weak capacitor causes repeated failed start attempts, which you hear as clicking.

Before you call, there are a few safe checks you can do yourself. These won't diagnose the problem, but they can rule out simple causes and give us useful information.

Check the outdoor condenser unit: - Look through the grille for visible debris - leaves, sticks, or small objects near the fan blade. - Do not reach inside the unit. Do not remove the top panel. - If you see something obvious, note it for when you call.

Check the air filter: - A severely clogged filter restricts airflow and forces the blower motor to work harder, which can cause rattling and strain-related noises. - If the filter is visibly grey and packed with dust, replace it with the correct size before calling.

Listen carefully and note the sound: - Where is it coming from - indoor unit, outdoor unit, or the ductwork? - When does it happen - startup, steady operation, or shutdown? - Is it constant or intermittent?

This information helps us narrow the diagnosis before we arrive.

When to stop and call immediately: - The sound is sudden, loud, or metallic (banging, grinding, screeching). - You hear hissing near the refrigerant lines or indoor unit. - The system shuts itself off after making the noise. - You smell burning plastic or electrical odor near the air handler.

> If you smell burning or see smoke, shut the system off at the thermostat and the breaker. Call (208)916-1956. Do not restart the system.

> If you or anyone in the home has a headache, nausea, or dizziness and the HVAC system has been running, get to fresh air immediately. Seek medical help if symptoms are present. Then call us. These can be signs of carbon monoxide exposure.