Aquavar ABII AB2S010 is a variable‑speed pump controller that uses a built‑in PLC to modulate motor frequency and maintain constant pressure via an integrated pressure transducer. Common failure modes include loss of power or ground fault on the 115/230 V supply, tripped contactor or relay contacts due to overheating, corrupted control board firmware, and degraded pressure sensor wiring or transducer output. First‑check diagnostics: verify input voltage and continuity of the power feed; inspect the motor contactors and relays for burn marks or loose connections; read any stored error codes from the controller’s LCD or diagnostic port; and perform a visual inspection of the pressure transducer cable for corrosion or disconnection.[oss-gpt-20b]