Flat Not Cold: Condenser Fins Caked in Exhaust Grease

A flat cooling poorly, with the outdoor unit positioned near the exhaust from commercial kitchens below. Its coil carries a dark, tacky coating. The indoor unit is clean and cooling weakly rather than not at all.

An outdoor coil this heavily coated explains the loss without anything else being wrong, so the diagnosis takes moments and the useful part of the visit is what comes after it. A coil in ordinary air takes years to reach this state. One sitting in a stream of cooking exhaust reaches it within months, which makes the position the fault rather than the maintenance. That distinction decides what the household should spend money on.

Cooking exhaust carries oil in fine droplets that stay airborne and settle on whatever they meet. An outdoor unit draws large volumes of that air through its coil every hour it runs, concentrating on the fins what the surrounding air holds thinly. The film insulates the metal and blocks the gaps between fins at the same time, so both heat transfer and airflow fall together. The equipment is correct and the position it was given is not.

Degreasing restores the coil until the film rebuilds on it. What actually changes the outcome is addressing the exposure: relocating the unit clear of the exhaust plume, or fitting a barrier that keeps the plume off the intake face. Cleaning more often manages a problem that siting created, and over any real span of years it costs considerably more than dealing with the position once.