Quality / Service Technical Reference
Unit Will Not Power On - Missing Fuse Holder and Fuses
Affected model: AOTG30LFTC
A quality assurance investigation was completed after an AOTG30LFTC outdoor unit could not be powered on. Inspection found that the fuse holder and fuses were missing from the outdoor unit.
Affected Unit
| Model | AOTG30LFTC |
| Serial number | T014795 |
| Reported symptom | Unit could not be powered on |
Reported Problem
The technician found that the fuse holder and fuse components were missing from the outdoor unit.
Sample Unit Inspection
The returned sample unit was inspected and the following physical evidence was recorded:
- The fuse holder, TLC 25A fuse and FSV 10A fuse were not attached.
- Marks were present where the fuse holder mounting screw had previously been fitted, indicating that the fuse holder had been installed at some point.
- Marks were present where fuse wiring had previously been connected.
- File/tool marks were visible on the PCB.
- The FSV 10A fuse was not fitted.
- The fuse cover and FSV 10A fuse were found loose/fallen.
Inspection finding: Physical marks indicated that the fuse holder and wiring had previously been fitted or connected.
Factory Operating Confirmation
The missing components were refitted to the sample unit:
- Fuse holder
- TLC 25A fuse
- FSV 10A fuse
After the components were correctly installed, the sample unit operated normally.
Manufacturing Record Check
The manufacturing record for the affected unit was reviewed.
Finding: No abnormality or problem was recorded when the product was manufactured.
Reproduction Test and Suspected Cause
FGL reproduced a condition consistent with the reported failure.
The suspected sequence was:
- The TLC 25A fuse was absent.
- The fuse wiring was connected directly to the terminal.
- The indoor unit was then powered on.
- This condition caused the FSV 10A fuse to short/fail.
Reproduction result: The condition could be recreated during testing using the above wiring arrangement.
Investigation Conclusion
Based on the physical evidence, factory operating confirmation, manufacturing records and reproduction testing, FGL's opinion was that the reported condition did not originate from the factory manufacturing process.
Conclusion: The investigation indicated that the fuse holder/fuse arrangement had likely been altered after manufacture rather than omitted during factory assembly.
Service Guidance
- If an AOTG30LFTC will not power on, inspect the outdoor electrical section for the presence and condition of the fuse holder and associated fuses.
- Confirm that the TLC 25A and FSV 10A fuse arrangements match the wiring diagram.
- Do not bypass the fuse holder or connect fuse wiring directly to terminals.
- Inspect the PCB, terminals and wiring for signs of modification, tool marks or previous repair work.
- Where components are missing or wiring has been altered, photograph the condition before rectification.
- After restoring the correct fuse arrangement, confirm normal unit operation.
Information to Collect if Escalating
| Item | Details Required |
|---|---|
| Unit identification | Full model and serial number |
| Fuse arrangement | Confirm whether TLC 25A and FSV 10A fuses and holder are fitted |
| Evidence | Photos of fuse holder, fuses, PCB and terminal wiring before repair |
| Modification history | Any known service, repair or electrical work performed previously |
| Test result | Whether the unit operates after restoring the correct fuse arrangement |
Safety: Isolate the electrical supply before inspecting or replacing fuse components. Electrical testing and wiring repairs must only be completed by suitably qualified personnel.