Cafe Unit Barely Cooling: Years of Grease Sludge on the Evaporator Coil

• –Compressor running and cycling normally — no short-cycling, no overload trips, no abnormal sound from the outdoor unit.
• –Airflow strength was normal but supply air temperature was several degrees warmer than expected for the set point — heat exchange was compromised, not airflow.
• –Evaporator coil fins were completely caked with a thick layer of orange-brown residue — a mixture of cooking grease, dust, and biofilm that had built up over years of operation in a food-service environment.
• –The buildup extended deep into the coil — surface cleaning during general servicing had only touched the outermost layer, leaving the interior blocked.

The evaporator coil had accumulated years of grease-laden dust and biological growth across its entire depth. In a cafe environment, airborne cooking oil particles settle on the wet coil surface and bind with dust, forming a sticky residue that hardens over time. General servicing cleans the filters and drain pan but does not disassemble the unit or apply chemical solution to the coil fins. Each quarterly service restored filter airflow but left the coil insulation untouched — a steady decline in heat exchange that looked identical to a compressor losing capacity.

We recommended a full chemical overhaul rather than compressor replacement. The unit was dismounted from the wall, the coil assembly was stripped down, and an alkaline chemical solution was applied under pressure to dissolve the grease and biofilm. The drainage system was also flushed. After reassembly, we ran the unit and measured supply air temperature — it had dropped significantly compared to before the overhaul, confirming the coil was now exchanging heat properly.

Full cooling restored after the chemical overhaul. No compressor replacement needed, no parts required. We recommended switching to six-monthly chemical overhauls given the grease-heavy environment — general servicing alone would not prevent the same buildup from returning.

Why general servicing stops working in food-service environments.

• –General servicing cleans filters, flushes the drain line, and wipes down accessible surfaces. It does not touch the evaporator coil fins. In a clean home, that is enough for years. In a commercial environment with cooking grease, dust, and heavy use, the coil accumulates residue that general servicing cannot reach.
• –Grease and biofilm insulate the coil surface. Refrigerant still flows and air still blows, but heat exchange drops because the fins cannot make contact with the passing air. The compressor works harder for less result — which looks exactly like compressor weakness from the outside.
• –A chemical overhaul strips the indoor unit down and pressure-washes the coil with alkaline solution. It is the only way to remove deep-seated buildup. If cooling returns after an overhaul, the compressor was never the problem.