Century motor replacement
AO Smith's Century brand produces replacement motors for most residential pump applications. For an AO Smith jet pump that has a failed motor but a functional pump end, Century replacement motors are the cost-effective repair option. Identify the motor frame size (NEMA frame number -- stamped on the existing motor nameplate), voltage/phase, and HP. Century sells replacement motors matching these specifications through electrical supply distributors (Rexel, Wesco, WESCO) and pump supply dealers. Cost: $80-$200 for a replacement motor vs $250-$400 for a full pump replacement. Motor-only replacement is practical for jet pumps where the pump end is accessible; submersible motor replacement requires pulling the pump from the well.
Pressure switch -- Square D 9013 series
The pressure switch on AO Smith well systems is typically a Square D 9013 series (or equivalent) -- a 30-50 or 40-60 PSI switch with an adjustable differential. These are universal components, not AO Smith-specific. Purchase at any electrical supply house ($25-$50). Replace the switch by: (1) shutting off power at the breaker; (2) removing the existing switch from the supply piping (1/4-inch NPT connection with a tee fitting); (3) threading the new switch onto the same tee; (4) reconnecting the wiring per the terminal labels (L1, L2 for 240V; T1, T2, and ground). Adjust the cut-in pressure by turning the main spring nut; adjust the differential by turning the range spring nut.
Impeller and diffuser service
The pump end of an AO Smith jet pump consists of an impeller and diffuser. If the pump motor runs but flow is reduced (decreased GPM without a change in well yield or pressure switch settings), the impeller may be worn or debris-clogged. Disconnect power and water, remove the pump end from the motor (typically 4 bolts), and inspect the impeller. Replace the impeller and diffuser set (Sold as a matched set -- order by AO Smith model number from a pump supply dealer, $40-$100) if the impeller is damaged. Clean if only clogged.
AO Smith warranty service
AO Smith backs residential well pumps with a limited warranty (typically 1-3 years depending on model). Contact AO Smith at 1-800-527-1953 with the pump model and serial number for warranty service. Parts and service for well pumps are provided through AO Smith's licensed pump contractor network rather than direct consumer service. Retain proof of installation by a licensed contractor to validate warranty coverage -- self-installation may void warranty coverage on submersible models.