New install cooling issue traced to swapped control wires
Aircon case in Bukit Panjang, Singapore: post-service issue traced to two indoor-to-outdoor signal wire pairs were swapped after targeted diagnosis checks.
Case details
What client reported
Two rooms sometimes ignored commands and cooled unevenly. The behavior changed depending on which zone was started first.
What we found
The pattern suggested a control-link issue, so we checked terminal mapping before any part replacement.
- Power supply and protection readings were stable
- Zone behavior changed based on start order
- Terminal labels did not match actual zone response
- Two signal wire pairs were swapped at the interconnect point
During install, two indoor signal wire pairs were landed on the wrong terminals. Commands reached the wrong zones and caused erratic behavior.
What we did
No major part replacement was needed. We corrected terminal mapping, checked each zone, and confirmed stable operation across all rooms.
Each room responded correctly after rewiring. Cooling and command behavior became consistent.
Timeline
Day 1
Newly installed system showed unstable zone behavior
Day 1
We traced each terminal pair and saw two zone links were reversed
Day 1
Signal wire pairs remapped and verified
What we learned
Why new systems can fail from mapping, not hardware.
- New equipment can still behave poorly if wiring assignments are wrong.
- Zone behavior that changes with start order is a strong mapping clue.
- Terminal verification should happen before any outdoor-unit replacement decision.
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