The Gardner Denver 89864799 is an AirSmart compressor controller that monitors pressure set points, alarm thresholds and language settings while managing low‑voltage 24 VDC operation for both variable‑ and fixed‑speed compressors. Common failure modes include loss of power or voltage drop at the 24 VDC input, faulty LCD/indicator panels, misconfigured pressure set points leading to runaway compressor cycles, and internal relay or contactor wear that disrupts compressor regulation. First‑check diagnostics: verify a stable 24 VDC supply to the controller, inspect all I/O connections for corrosion or loose contacts, examine the LCD/indicator panel for display faults, and review any stored error codes via the controller’s diagnostic interface.[oss-gpt-20b]