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AC Running but House Stays Humid
in Spokane, WA
Spokane's normal summer air is dry, but afternoon thunderstorms in July and August can push indoor humidity up fast. Your AC is supposed to pull moisture out of the air as it cools it. If the system isn't doing that, the air feels clammy even when the temperature is right. This usually means the unit isn't running long enough or isn't operating at the right pressure to remove moisture.
Quick Answer
An AC that cools but doesn't dry the air is usually oversized, running too short of cycles, or has a refrigerant problem. Spokane summers are normally dry, but when humidity spikes after afternoon thunderstorms, an oversized or poorly tuned system can't wring the moisture out before shutting off. Call (509) 472-2017 to have the system checked and the refrigerant charge verified.
Telltale Signs
Warning Signs to Watch For
- Indoor humidity stays above 60 percent even with the AC running
- Windows fog up on the inside during humid evenings
- The house feels sticky and heavy even when the thermostat shows a comfortable temperature
- Condensation appears on cold surfaces like drinks or tile floors
- A musty smell builds up in the house after a few humid days
Root Causes
What Causes AC Running but House Stays Humid?
Oversized Unit Short Cycling
Removing humidity from the air takes time. The AC has to run long enough for moisture to condense on the evaporator coil and drain away. An oversized unit cools the air temperature so fast that it shuts off before it can dehumidify. Spokane homes that had large units installed in the late 1990s often run into this problem every July.
The Fix
System Sizing Review and Replacement
The fix is a correctly sized unit that runs in longer cycles. In some cases, a whole-home dehumidifier can help manage humidity without replacing the unit right away, but the sizing problem doesn't go away.
Incorrect Refrigerant Charge
Humidity removal depends on the evaporator coil being cold enough that moisture condenses on it. If the refrigerant charge is off, the coil runs too warm and lets moisture pass right through into the house. Even a small variance from the correct charge level changes how well the system handles humidity.
The Fix
Refrigerant Charge Verification and Adjustment
A tech checks the charge against the manufacturer's specifications for your outdoor temperature conditions. Getting the charge exactly right often noticeably improves how the system handles humid days.
Self-Diagnosis
Which Cause Applies to You?
Check the signs you're observing to narrow down the likely root cause before your inspection.
| What You're Seeing | Oversized Unit Short Cycling | Incorrect Refrigerant Charge |
|---|---|---|
| System cools the house in under 10 minutes and shuts off frequently | ||
| Humidity problem is worse on days over 90 degrees when the system runs longer | ||
| Problem started after a refrigerant service by another company | ||
| Humidity is fine in winter with a heat pump but bad every summer with AC | ||
| Evaporator coil looks dry when the system is running on a humid day |
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