R-Pro › Field cases › Components
Check Valve Back-Flow — Condenser to Evaporator Leakage
Likely causes
Disc/ball seat face worn — cannot fully seal
Check: After compressor stops, watch low-side gauge for rapid rise within 1~2 min — abnormally fast pressure equalization suggests back-flow; isolate with bypass valve and measure differential (converging to 0 confirms)
What to do: Disassemble check valve → polish disc and seat (determine reusability) or replace new → always verify installation direction arrow during replacement → follow manufacturer torque spec
Spring fatigue fracture or foreign debris on seat
Check: Measure spring free length — replace if shortened more than 10% from normal; check for foreign debris (sludge, metal particles) on seat — also inspect oil separator condition
What to do: Replace spring with new; if cause is foreign debris, inspect oil separator and replace filter-drier; if cause is disc chattering from liquid flooding, readjust expansion valve superheat
Back-flow is easily caught by watching the low-side gauge rise within 1~2 minutes after compressor stops. Abnormally fast pressure equalization should immediately raise suspicion.
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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