R-Pro › Field cases › Air conditioning
AC Intermittent Cooling — Repeated Auto ON/OFF (Short Cycling)
Likely causes
Step 1 — Identify short-cycling cause (clearance, overcharge, EEV, sensor)
Check: Outdoor unit clearance insufficient = exhaust recirculates → condensing pressure spikes → high-pressure cutout → restart after cooldown. Overcharge = abnormal discharge pressure rise. EEV/TXV fault = subcooling hunting. Indoor temp sensor fault = false setpoint detection. Normal cycle = ≥7–10 min per run.
What to do: Measure airflow space around outdoor unit (insufficient = short cycling). Use manifold gauge for suction/discharge → distinguish overcharge / EEV fault / non-condensables. Read PCB error code or self-diagnostic for sensor faults. Time the cycle (normal ≥7–10 min).
Step 2 — Action by cause and verify normal cycling
Check: Insufficient clearance = relocate outdoor or remove obstacles. Overcharge = recover portion. EEV/TXV fault = clean or replace (self-test: listen for EEV click after system OFF). Sensor fault = measure resistance vs B-constant table, replace. Run 1 hour and verify ≥7 min per cycle.
What to do: Insufficient clearance = relocate outdoor or remove obstacles. Overcharge = recover excess and re-measure pressure. EEV/TXV fault = disassemble-clean or replace. Sensor fault = compare with B-constant table and replace. Run 1 hr after action and verify cycle ≥7 min.
Short cycling = directly shortens compressor life (peak load on start/stop). Cycle <5 min = diagnose immediately. Inverter units cycle less frequently — when they do, suspect PCB/communication fault. Educate user: have them log cycle time and count for 1 week.
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