R-Pro › Field cases › Heat pumps
Hot Gas Defrost Valve Stuck
Likely causes
Hot gas bypass solenoid valve coil burned out or open-circuit
Check: Inspect with instruments or visually
What to do: Measure solenoid coil resistance (typically 10–30Ω) — if open/burned, replace coil only (more economical than full valve replacement)
Mechanical seizure due to debris (sludge, metal chips) inside valve
Check: Inspect with instruments or visually
What to do: If coil is normal, measure coil voltage during valve open command — verify rated AC/DC voltage is applied
Sludge from degraded refrigeration oil blocking valve port
Check: Inspect with instruments or visually
What to do: Lightly tap valve body to attempt to free the stuck valve (temporary measure only)
Valve seat worn or corroded
Check: cannot fully open or close
What to do: Recover refrigerant, then disassemble and clean valve or replace — recommend line flushing before installing new valve
Open command is normal but valve fails to operate due to insufficient pilot line pressure
Check: Inspect with instruments or visually
What to do: For pilot-operated valves, inspect and clean pilot line filter
On-site valve stuck check: if outdoor coil temp does not rise within 30 seconds of defrost command, hot gas is not flowing — verify by checking temperature difference between valve inlet and outlet pipes.
All 565 cases work offline in R-Pro, with error codes for 62 brands and P-T data for 108 refrigerants.
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