The Vickers KDG4V‑5 is a 30 bar hydraulic proportional valve that uses a single‑solenoid throttle design to control flow in direct proportion to an electrical command signal. Common failure modes include loss of proportional response due to solenoid coil degradation, internal wear or contamination causing reduced flow accuracy, and electrical faults such as open/short circuits in the drive wiring or damaged contactors. For initial troubleshooting, verify that the supply voltage matches the valve’s rated 24 VDC (or specified) and measure coil resistance; check the hydraulic pressure on both inlet and outlet ports for abnormal drops or spikes; perform a visual inspection of the solenoid contacts and surrounding housing for corrosion, wear, or fluid ingress.[oss-gpt-20b]