One side of the room always warmer: stuck louver vane
One corner of the living room stayed warm while the rest cooled fine. The owner expected a failing compressor or low gas. A single stuck vane and a fouled coil section behind it were the whole story.
By Team Snowflake | Reviewed 3 Mar 2026
Case summary
Daikin Cassette6 years oldHDBGeylang, Singapore
- Concern
- Worry was that the compressor was failing or the gas charge was low.
- Found
- One louver vane stuck closed, coil fouling on that quadrant
- Key check
- Opened cassette panel and checked all four vane mechanisms in sequence
- Result
- Even cooling returned on the same visit with no parts needed. We advised servicing the cassette every six months, since units in sealed ceiling voids foul faster than wall-mounted ones.
What we were told
One side of the living room had stayed warmer than the other for about two months. The owner thought the unit was losing capacity, and a gas top-up had already been suggested. It had not been serviced in two years.
What we checked
Low gas would cool all four corners poorly and evenly, so the one-sided warmth pointed away from refrigerant before we opened anything. We took the cassette panel off and worked each of the four vanes by hand to feel for stiffness. Then we checked each coil section for fouling. The aim was to clear the mechanical causes that explain a single warm corner before going near the gas.
Three of the four vanes moved freely, opening and closing as normal.
The vane on the warm corner was seized near-closed. The motor still ran, but the linkage had locked up.
The coil section behind that stuck vane carried visible scale and dust the other three sections did not.
Gas readings came back normal on both sides, with the charge correct.
What we found
Each vane swings on a small pivot driven by a motor. Over two years without servicing, dust and moisture had built up on this vane's pivot until the friction was too high for the motor to move it. Stuck near-closed, the vane let almost no cooled air out of that corner. Less air over that coil section meant slower drying, so moisture lingered and pulled in more dust. The fouling fed on itself, which is why the warm corner crept worse across two months.
What fixed it
We cleaned the seized pivot and linkage with a degreasing solvent, then applied a light lubricant rated for the operating temperature. All four vanes were cycled several times to confirm smooth, full movement. The fouled coil section was cleaned to match the other three. We ran the unit for fifteen minutes and measured airflow at each outlet with a hand-held meter. All four corners read balanced and normal. No parts were replaced and no gas work was done. We advised a six-month service interval so the pivot does not seize again in the ceiling void.
Outcome
Even cooling returned on the same visit with no parts needed. We advised servicing the cassette every six months, since units in sealed ceiling voids foul faster than wall-mounted ones.
What this case teaches us
One warm corner points to one vane, not the whole system
- A cassette pushes cooled air through four separate vanes. When only one corner stays warm, the fault sits in that one vane, not the gas charge.
- Low gas would cool the whole room poorly and evenly. An asymmetric warm spot rules refrigerant out before any quote.
- Tell us which corner or side stays warm. That pattern alone tells us whether the fault is local or system-wide.
Related reading
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