R-Pro › Field cases › Components
Oil Return Line Check Valve Seized — Compressor Fails to Start
Likely causes
Foreign matter wedged in check valve ball/disc causes failure to close
Check: Measure pressure before and after check valve — reverse pressure above 0.05 MPa confirms seizure; touch oil return line during startup — warmth indicates backflow heating oil
What to do: Close oil return ball valve → remove check valve, inspect ball, spring, and seat → clean with solvent if sludge stuck; replace entire valve if ball surface scratched → manually verify directional flow after reassembly
Return line orifice clogged — oil level rises excessively in separator
Check: Check oil level via sight glass — if above 1/2, suspect orifice clog; typical orifice diameter 0.8–1.2 mm
What to do: If orifice clogged, drill clear or replace orifice → drain oil to return level to 1/2 then resume operation
When compressor fails to start, touch oil return line by hand — if warm, high likelihood of check valve backflow since reverse pressure heats the oil
All 565 cases work offline in R-Pro, with error codes for 62 brands and P-T data for 108 refrigerants.
Open R-Pro →Related cases
- Liquid Refrigerant Entering Compressor (Flooded Start / Liquid Slugging)
- Compressor Motor Burnout / Ground Fault
- High Compressor Discharge Temperature (>107°C scroll, >120°C recip)
- Scroll Compressor Reverse Rotation — 3-Phase Miswiring
- Scroll Tip Seal Wear — Volumetric Efficiency Loss and Reduced Cooling Capacity
- Scroll Poppet Valve Fails to Close — Reverse Rotation Noise After Shutdown