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The compressor in a central AC system starts and stops dozens of times on a hot day, and the contactor and capacitor absorb that cycling every time. Homes in Washington County, MO run cooling about three months a year, from June through August. By late summer, a unit that has run hard through June, July, and August has put real hours on those parts. A contractor diagnosing a fault here checks the capacitor first, because a weak one causes the compressor to strain on startup and can take out the contactor shortly after. Both components are inexpensive to replace and expensive to ignore.
Ducting in a house this old was sized and routed for whatever system replaced the original, and that system was itself often replaced again. By the time a contractor opens the current unit, the equipment may be well into a product cycle its manufacturer has already closed. Half the homes in Washington County, Missouri were built in 1985 or earlier (2020-2024 ACS 5-year). That matters for repair work specifically: a failed capacitor or contactor on a newer model ships the next day, but a board or motor on a unit that was mid-life when this county's median house already had two owners behind it can take days to source or cannot be sourced at all. That gap between what the house has and what parts suppliers stock is where repair jobs in Washington County stall.
The Parts of a Central AC a Contractor Checks During a Repair
The outdoor condenser unit sits outside the house, usually on a concrete pad, and it carries the compressor and the condenser coil. These are the pieces a contractor reaches first when the system stops cooling. Inside, the air handler or furnace holds the evaporator coil, which is a common failure point when airflow drops or the unit freezes up.
The refrigerant lines run between the two units, and a leak anywhere along them shows up as lost cooling capacity. The thermostat on a wall inside the house controls the whole system, and a fault there can look exactly like a mechanical breakdown elsewhere.
The drawing shows a typical layout, and a licensed contractor determines which components are relevant to your specific house and system.
Get matched in Washington CountyWashington County, Missouri, by the numbers
64 severe weather events were recorded in Washington County, Missouri between 2015 and 2024.
NOAA National Centers for Environmental Information, Storm Events Database, bulk CSV export, events 2015-01-01 through 2024-12-31.Half the homes in Washington County, Missouri were built in 1985 or earlier (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesWashington County, Missouri holds 10,734 housing units (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesOwners occupy 78.4% of the occupied homes in Washington County, Missouri (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesRules & Standards Behind Central AC Repair in Washington County, Missouri8 sourced rules and standards
What HVAC Repair Looks Like in Washington County
Split-system central air conditioners rated below 45,000 Btu/h manufactured on or after January 1, 2023 must meet a federal minimum of 13.4 SEER2.
Split-system central air conditioners rated at or above 45,000 Btu/h manufactured on or after January 1, 2023 must meet a federal minimum of 13.4 SEER2.
Split-system central air conditioners manufactured between January 1, 2015 and December 31, 2022 had to meet 13 SEER, the metric that preceded SEER2.
Single-package central air conditioners manufactured on or after January 1, 2023 must meet a federal minimum of 13.4 SEER2.
Space-constrained central air conditioners manufactured on or after January 1, 2023 must meet a federal minimum of 11.7 SEER2.
Federal efficiency standards for split-system central air conditioners and heat pumps are set on each certified combination of outdoor unit and indoor coil rather than on the outdoor unit alone.
Residential and light commercial air conditioning and heat pump systems assembled in the field, including mini-splits and unitary systems, may not be installed on or after January 1, 2025 using a refrigerant with a global warming potential above 700.
A field-assembled system whose specified components were all manufactured or imported before January 1, 2025 carries no installation compliance date under the refrigerant restrictions and may still be installed.
Severe Weather Events in Washington County
Extreme weather puts real stress on central AC systems, cycling them hard and shortening the life of components that are already working against the heat. How much of that load a system carries depends on what the local climate actually delivers, which is why the record below is part of the picture for repair work in Washington County.
64 severe weather events, 2015–2024. Source: NOAA National Centers for Environmental Information, Storm Events Database.