CH38 in One Bedroom Only: Pinhole Leak in That Indoor Coil

One bedroom losing cooling steadily while every other room on the same system continues to perform normally. The outdoor unit is behaving exactly as it should. The affected indoor unit is clean and its filter is clear.

A single room failing on a shared system points into that room, and on a refrigerant fault the candidates in one room are short. The branch pipework serving it, the connections at either end of that branch, and the coil inside the unit itself. Testing the branch and its joints separately from the coil is what distinguishes a pipe repair from a part replacement, and the two cost very different amounts. It is worth doing properly before anyone commits.

An indoor coil is thin-walled tube in close contact with fins and moisture, sitting in a wet environment for hours a day. Corrosion can start where the tube meets a fin, or where a manufacturing stress concentrates, and it works through the wall to a pinhole. The loss is slow because the opening is small. It will not be found by examining any joint, because no joint is involved.

Replacing the coil as a component, then evacuating and charging the system properly, is the repair. The cost is real and it deserves an honest comparison against the value of the unit it sits in. On an older indoor unit, replacing the whole unit is sometimes the better answer, and the way to settle that is to price both rather than to assume either.