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AC Short Cycling
in Spokane, WA
A normal AC runs in cycles of 15 to 20 minutes. If yours is turning off after 2 or 3 minutes and then starting right back up, something is wrong. Short cycling is hard on every part of the system, especially the compressor, because starting up is the hardest work a compressor does. The longer this goes on, the more damage it causes.
Quick Answer
Short cycling means the AC starts, runs for a minute or two, shuts off, then starts again. It usually points to a refrigerant problem, an oversized unit, or a failing compressor. Spokane homes that had AC units added in the 1990s often got units that were oversized. Call (509) 472-2017 because short cycling puts hard wear on the compressor every time it starts.
Telltale Signs
Warning Signs to Watch For
- The outdoor unit turns on and off more than three times in 10 minutes
- The house never fully cools down even though the system runs constantly
- You can hear the compressor starting up over and over from inside the house
- The circuit breaker trips after several short cycles in a row
- The system runs fine for a few hours then starts cycling rapidly when the outdoor temperature peaks
Root Causes
What Causes AC Short Cycling?
Oversized AC Unit
A unit that is too large for the home cools the space so fast that the thermostat is satisfied before the system completes a proper cycle. It shuts off, the temperature creeps back up, and it starts again within minutes. Many Spokane homes that added AC in the early 1990s got units that were sized too large, often because contractors used rough estimates instead of proper calculations.
The Fix
Load Calculation and System Replacement
The only real fix for an oversized unit is replacing it with a correctly sized one. A proper load calculation accounts for your home's square footage, insulation, window area, and orientation.
Low Refrigerant or Refrigerant Overcharge
Both too little and too much refrigerant cause pressure problems that make the system's safety controls shut it off early. This creates a rapid on-off pattern that looks similar to an oversized unit but is usually more erratic. Spokane's dry heat accelerates small leaks as metal components expand during hot afternoons.
The Fix
Refrigerant Level Check and Correction
A tech measures the refrigerant charge and adjusts it to the correct level. If it's low, they find and fix the leak first. If it's overcharged from a previous service, they recover the excess.
Failing Compressor
A compressor that is wearing out will often overheat quickly and trigger its internal protection switch. That shuts the system off, the compressor cools down, then it tries to start again. Units that have been short cycling for any reason end up with compressors that fail faster because every startup puts stress on the windings.
The Fix
Compressor Diagnostic and Replacement
A tech checks compressor amp draw and temperatures to confirm it's failing. Compressor replacement is a major repair, and sometimes replacing the full outdoor unit makes more financial sense depending on the age of the system.
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 AC Unit | Low Refrigerant or Refrigerant Overcharge | Failing Compressor |
|---|---|---|---|
| House reaches set temperature in under 5 minutes on a 90-degree day | |||
| Refrigerant lines show frost during short cycling episodes | |||
| Outdoor unit feels extremely hot to the touch before shutting off | |||
| Short cycling started right after a refrigerant recharge by another company | |||
| Unit is less than 5 years old but cycles rapidly from day one | |||
| Compressor hums loudly and then cuts out within 60 seconds |
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