Bad Smells in Cheney, WA

AC smells fall into a few distinct categories. Each one points to a different part of the system.

Musty or Moldy Smell

This is the most common complaint we hear from Cheney homeowners, especially after the first hot stretch of the year. The cause is almost always moisture sitting somewhere it shouldn't.

The condensate system is the first place to look. Your AC pulls humidity out of the air and that moisture drains away through a condensate pan and drain line. When that line clogs - and it does clog, with algae, dust, and debris - water backs up and sits. Standing water in a dark, warm environment grows mold and mildew fast.

The evaporator coil itself can also harbor mold. The coil sits inside your air handler and gets cold and wet every time the system runs. If airflow is restricted or the coil doesn't dry out properly between cycles, biological growth takes hold on the coil surface and gets pushed through your vents every time the fan runs.

Ductwork is the third culprit. Cheney has seen significant housing growth over the past 15–20 years, and a lot of that construction used builder-grade duct systems - flex duct with thin liners, minimal insulation, and connections that weren't always sealed well. Over time, those ducts can accumulate moisture, especially in unconditioned spaces like crawlspaces or attics. Wet duct liner is a mold factory. No amount of coil cleaning fixes that.

Burning Smell

Dust burning off at the start of the season is normal and short-lived. If the smell persists or smells like plastic or electrical components, that's different.

Electrical burning smells can come from a failing capacitor, a motor winding that's starting to break down, or wiring that's overheating. These are not DIY fixes. Shut the system off and call.

A burning smell from the vents combined with reduced airflow can mean a blower motor is working too hard - often because of a dirty filter or a restriction in the duct system. The motor overheats, and you smell it.

Dirty Sock Syndrome

This one has an actual name in the industry. It's a sharp, locker-room odor that hits when the system first starts up, then fades. It's caused by bacterial growth on the evaporator coil - a specific type of bacteria that thrives on the coil surface during the off-cycle when the coil is warm and damp.

It's more common in systems that cycle frequently or sit idle for long stretches. Homes near Eastern Washington University's campus that sit empty over summer breaks, for example, can fire up in the fall with this exact problem.

Chemical or Sweet Smell

A sweet, chemical odor - sometimes described as ether or acetone - can indicate a refrigerant leak. Refrigerant itself isn't typically dangerous in small amounts in a well-ventilated space, but a leak means your system is losing its ability to cool and the root cause needs to be found and repaired, not just recharged.

Before you call, here are a few things you can check safely:

• Check your air filter. A clogged filter restricts airflow, causes the coil to stay wet longer, and can contribute to both musty smells and burning odors. If it's gray and packed, replace it.
• Look at the condensate drain pan (usually visible under the air handler). If there's standing water or visible slime, the drain line is likely clogged.
• Check your vents and registers for visible mold or dust buildup around the grilles.
• Run the system for 15 minutes and note whether the smell gets stronger, fades, or changes character. That information helps us diagnose faster.
• Check your CO detectors to confirm they're functional and not expired. Replace batteries if needed.

Do not open the air handler cabinet, handle refrigerant lines, or attempt to clear a drain line with anything other than water or a wet-dry vac. If you're not sure, stop and call.