Two bedrooms losing cooling together: pinhole coil leak
Two bedrooms kept losing cooling together, while the living room held. Repeated gas top-ups bought a few cold days, then both rooms went warm again. The owner feared the whole multi-room setup needed replacing. The fault was much smaller, and on one coil.
By Team Snowflake | Reviewed 3 Mar 2026
Case summary
Panasonic Wall-mounted9 years oldHDBSembawang, Singapore
- Concern
- Worry was that the entire multi-room setup needed full replacement
- Found
- Pin-hole leak at indoor coil return bend on one fan coil
- Key check
- Combined pressure hold with targeted dye and bubble tracing around coil return bends
- Result
- The targeted repair held the pressure retest. Steady cooling returned to both bedrooms, and the repeat top-up cycle stopped. No coil was replaced.
What we were told
Both bedrooms cooled well for a while after each top-up, then went warm again together. The living room stayed cooler than the bedrooms the whole time. The owner had paid for several top-ups already and wanted to know if the setup needed replacing.
What we checked
Two rooms fading together while the living room held pointed to the shared bedroom branch, not a system-wide gas problem. We ran a pressure hold test first to confirm the system was actually losing gas, rather than topping it up blind. With leakage confirmed, we worked inward. The pipe joints at each indoor unit were checked with soap solution, since loose joints are a common leak point and quick to rule out. Those came back clean, so we moved to the coils, adding UV dye at the service port and running the system under load to carry it through the indoor units.
Operating pressure sat below the expected range, confirming gas was leaking out.
The two bedrooms on the shared branch declined first; the living room held.
Soap-solution checks at every indoor pipe joint stayed clean.
UV dye traced the leak to one return bend on a single indoor coil.
What we found
A pin-hole leak had opened at a return bend on one indoor coil. Return bends are the tight U-shaped copper sections that join the coil tubes. They take the most stress as the coil warms and cools each cycle, so over years a tiny crack can form and let gas seep out slowly. That explains the pattern. Both bedrooms drew from the same gas branch as the leaking coil, so each room lost cooling at the same pace. The living room sat on a separate branch that still held enough gas.
What fixed it
We laid out two options. The first was a targeted copper repair at the confirmed return bend, which seals the pin-hole and keeps the existing coil. The second was a full coil replacement, more thorough but far more costly and with longer downtime. The leak was a single point, and the rest of the coil showed no corrosion. On that basis we recommended the targeted repair, and noted that if the seal held a pressure retest, the system would run normally with no major part replaced.
Outcome
The targeted repair held the pressure retest. Steady cooling returned to both bedrooms, and the repeat top-up cycle stopped. No coil was replaced.
What this case teaches us
A repeating gas top-up means find the leak, not refill it
- If cooling fades again weeks after a top-up, gas is leaking out somewhere. Refilling treats the symptom, not the cause.
- Which rooms lose cooling, and which hold, narrows the search. Two bedrooms fading together pointed to one shared branch, not the whole system.
- A confirmed single leak point can often be sealed at the coil. Ask whether a targeted repair fits before agreeing to replace the unit.
Related reading
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