LG CH38 on a Cassette: A Loose Fitting, Not Corrosion

A cassette code raises talk of corroded pipework or an ageing system. Whether the fault is decay or something never done correctly.

By Team Snowflake | Updated 24 Aug 2026

How this presents

A fault code showing on a unit that is cooling poorly, on a system with no visible corrosion anywhere on it. Pipework and connections look sound throughout. The loss appears to have been gradual and constant rather than sudden.

Setup: LG Cassette10-12 yearsCondoBukit Panjang
Misread as: Corroded pipework needing sections replaced, or a system approaching the end of its life.
Check first: Whether the pipework shows corrosion at all before the joints are examined

What else produces this

Clean, sound-looking pipework changes the shape of the search rather than ending it. Refrigerant escapes through openings, and an opening does not require damaged metal: a joint that was under-tightened, over-tightened or made up on an imperfect surface will pass gas from the day it was assembled. Checking the joints themselves, rather than the pipe, is what separates this from a corrosion problem.

No visible corrosion anywhere on the exposed pipework removes the usual explanation.
A gradual constant loss rather than an abrupt one fits a small permanent opening at a joint.
A connection at the outdoor unit found loose accounts for the escape without any damage.
Sound metal and clean sealing surfaces at that joint show it can be remade rather than replaced entirely.

Why it happens

A flared connection seals by pressing a shaped copper face against a fitting under controlled force. Too little force and the faces never seat fully. Too much and the flare distorts and cracks. Either way the joint passes refrigerant slowly from the moment it is made, and a system can run for years before enough has escaped to affect the cooling anyone notices. Nothing has degraded at all; it was never right in the first place.

What resolution involves

Remaking the connection to the correct specification and recharging the system is a short repair on components that are otherwise sound. The wider point is about assumptions. An ageing system with a leak is not automatically a corroded system, and checking the joints before condemning the pipework can be the difference between an hour of work and a section replacement.

How to tell it worked

Pressure held after the joint is remade, tested before the system is charged. A joint that seals correctly does so immediately, so there is no reason to prove it with refrigerant in the system.

Before you approve a quote

A leak does not need damaged metal to exist

A joint made up incorrectly leaks from the day it was assembled, on pipework that looks perfect.
No visible corrosion narrows the search to the joints rather than ending it.
Check the connections before condemning the pipe. One is an hour of work and the other is not.

Questions this case answers

Can a nine-year-old aircon losing gas still be worth repairing?

Yes, and it is more common than the age of a system would suggest. A joint that was never made up correctly passes refrigerant slowly from the start, and it can take years for enough to escape to be noticed.

How does a pipe fitting work loose without any corrosion?

Corrosion is visible on the pipe and usually affects a length of it. A joint problem sits at a connection on otherwise sound metal, and the loss tends to be slow and steady rather than accelerating.

What happens if the leak point is never actually found?

Both under-tightening and over-tightening cause it. The seal depends on a specific force applied to a correctly shaped face, so too little never seats and too much distorts or cracks the flare.

Can the same loose fitting turn up on other units of similar age?

Usually, yes. Where the metal and the sealing faces are sound, the joint is remade and the system recharged. Replacement only comes in where the flare itself has cracked or the fitting has been damaged.

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