Compressor oil acidity test — using an Acid Test Kit and interpreting results

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Types of acid test kits and oil sampling procedure. Check: Kit types: ① Color-change (most common) — drop the sample in the reagent vial; yellow → red/green color shift. Fast and cheap (field). ② Titration — exact mgKOH/g value. For lab/precision work. Sampling: ① After operating, stop the compressor for 30 min (oil settles at the bottom). ② Take from the compressor's own oil port or sight glass, not from the liquid line. ③ About 30–50 mL into a clean sample bottle. ④ At sampling, also log ambient temperature, runtime and compressor temperature. What to do: Safety: ① When sampling, recover refrigerant or stop the system and confirm pressure safety. ② Acidic oil irritates skin and eyes — wear gloves and goggles. ③ Reagents may be flammable/hazardous — ventilate, keep away from children/food. ④ Dispose of sample bottle and used reagent per environmental regulations. ⑤ Check kit expiration (usually 2–3 years) — expired reagent gives unreliable color shifts. Interpreting results + actions — color-change kit reference. Check: Result tiers: ① Yellow/pale yellow — normal (≈0–0.05 mgKOH/g). No action. ② Orange/pale red — borderline (0.05–0.1). Monitor and retest at next service. ③ Deep red/dark — acid progressing (>0.1). Action required. ④ Black/brown + burnt smell — suspect burnout (see prior compressor-motor-overheat case); beyond a routine acidity issue. Compare against the kit's color chart under daylight or white LED — fluorescent lights can distort the color. What to do: Tiered actions: ① Normal — only retest at the next scheduled service. ② Borderline — replace the filter-drier (it adsorbs acid) + audit operating conditions (ambient, load). Retest in 1–2 months. ③ Acid progressing — a) recover system → replace compressor oil with the same type/viscosity (e.g., POE replaces POE) → install a fresh filter-drier and an acid burnout filter-drier in the liquid line → evacuate → recharge. b) Retest in 1 week. If acid progresses again, suspect burnout. ④ Burnout — apply the clean-up procedure from the compressor-motor-overheat case.

Compressor oil acidity test — using an Acid Test Kit and interpreting results

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Types of acid test kits and oil sampling procedure

Interpreting results + actions — color-change kit reference

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