R-Pro › Field cases › Air conditioning
AC Weak Cooling — Comprehensive Diagnosis (Filter, Coil, Refrigerant, Airflow)
Likely causes
Step 1 — Air-side check (filter, indoor coil, outdoor coil, airflow)
Check: Filter = most common cause (overall #1). Clogged → 30–50% airflow drop → evaporator coil freezes. Indoor coil = dust/mold fouling reduces heat exchange. Outdoor coil = leaves/debris/dust = higher condensing pressure. Blower = verify RPM (variable or fixed speed).
What to do: Replace/clean filter (every 3 months). Indoor coil = spray coil cleaner then vacuum. Outdoor coil = soft brush leaves/dust + use fin comb if aluminum fins are bent. If blower RPM is off = inspect motor/blades (separate case).
Step 2 — Refrigerant-side check (superheat, subcooling, pressure, leak)
Check: High superheat + low subcooling = undercharge = suspect leak → trace with detector. Low superheat + high subcooling = overcharge. Low suction + normal discharge = clogged TXV/EEV or liquid line restriction. Both suction and discharge high = non-condensable gas (air/moisture) contamination.
What to do: Undercharge = trace leak → repair → vacuum → recharge by weight (see separate case). Overcharge = recover portion with recovery unit. TXV/EEV blocked = disassemble/clean or replace. Non-condensables = full recovery → vacuum → recharge by weight.
Weak cooling = compound causes more common than single. Diagnose air-side → refrigerant-side. Never blindly add refrigerant (unrepaired leak + overcharge = compressor damage). Record all 5 datasets (indoor/outdoor temp + airflow + pressure + superheat/subcool).
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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