A whistling sound from your AC isn’t always a sign of serious damage, but it’s not something to ignore either. Usually it’s the system telling you air is being forced through somewhere it shouldn’t. Here’s what causes an AC to whistle and what to do about it.

What Causes the Whistling

Restricted airflow

This is the most common cause. A clogged filter, blocked vent, or closed registers force the blower to push air through a tight space, which creates a high-pitched whistle. The fix is often as simple as a new filter and open vents.

Leaky or undersized ductwork

Air escaping through gaps in your ducts, or moving too fast through ducts that are too small, whistles as it goes. This is common in older or poorly designed duct systems.

A refrigerant leak

A hissing or whistling near the refrigerant lines can mean escaping refrigerant under pressure. This one needs a pro, and soon.

A failing expansion valve or compressor

High internal pressure can produce a whistle from the system’s components, a more serious cause worth diagnosing.

Don’t Let It Whistle On

Start with the filter and vents. If the whistle continues, restricted airflow is straining your system and driving up your bills, and a refrigerant or component issue only gets worse with time.

Track Down the Source

If a fresh filter doesn’t quiet it, Bearcat will find what’s causing the whistle and fix it right. See our AC repair services, or call (509) 891-5110.