AOTG36LATL - Error 11 Investigation After ACTPM Replacement

This article summarises the quality assurance investigation into an AOTG36LATL where Error 11 remained after replacement of the ACTPM spare part.

Issue Summary
  • Outdoor unit: AOTG36LATL
  • ACTPM spare part number: 9707592016
  • Reported fault: Error 11 remained after ACTPM replacement
  • Returned ACTPM showed resistance values different from a normal sample on some terminal combinations.
  • Factory testing did not confirm a fault with the ACTPM itself.

Problem Description

An ACTPM spare part, part number 9707592016, was installed in an AOTG36LATL that was displaying Error 11. The replacement did not clear the error.

The ACTPM was subsequently returned for investigation. Resistance measurements taken in Australia showed differences compared with a normal ACTPM on some terminal combinations.

ACTPM Resistance Measurements

Tester (+)Tester (-)
TerminalReturned SampleNormal Sample
+-360 kΩ359 kΩ
+P874 kΩ707 kΩ
+N360 kΩ359 kΩ
-P506 kΩ248 kΩ
-N--
PN540 kΩ359 kΩ
Important: The original QA report states that there was no established residual impedance judgement criterion available at the time. The resistance values above should therefore not be used by themselves as a pass/fail specification unless an approved ACTPM judgement standard is available.

Factory Analysis

1. Returned ACTPM Check

  • The resistance readings reproduced the values previously measured in Australia.
  • FGE, the ACTPM manufacturer, inspected the returned component.
  • No fault was found with the ACTPM itself during the manufacturer's investigation.

2. Operational Test on Outdoor Unit

The ACTPM was connected to an AOTG36LATL outdoor unit and tested in operation.

  • The outdoor unit operated correctly.
  • Cooling operation was tested.
  • The unit was checked under conditions where operating current reached its maximum value.
  • No abnormal operation was identified during the test.

3. Assessment of Error 11

The factory did not consider the returned ACTPM to be directly responsible for the Error 11 condition.

Possible fault area: The QA report suggests the Error 11 may instead have been related to a transmission error between the Main PCB and Inverter PCB. The report also notes that the posistor may become active.

Investigation Conclusion

The factory was unable to identify a definitive root cause from the returned component and testing performed.

  • The returned ACTPM showed some resistance differences compared with a normal sample.
  • However, no ACTPM fault was confirmed by the component manufacturer.
  • The ACTPM operated normally when connected to an AOTG36LATL during factory testing.
  • The site Error 11 was therefore considered more likely to involve communication between the Main PCB and Inverter PCB than the ACTPM itself.
  • The factory advised that similar future cases should be monitored and investigated again if the issue recurs.

Service Guidance

If Error 11 remains after ACTPM replacement on an AOTG36LATL:

  1. Do not assume the replacement ACTPM is faulty solely because Error 11 remains.
  2. Confirm all ACTPM connections and terminal seating.
  3. Inspect wiring and connectors between the Main PCB and Inverter PCB.
  4. Check for poor contact, loose connectors, damaged harnesses or signs of overheating.
  5. Investigate the inverter power circuit and posistor condition in accordance with the applicable service manual.
  6. If resistance testing of the ACTPM is carried out, compare results only against an approved judgement criterion where one is available.
  7. If no fault can be identified and Error 11 persists, escalate the case with measured values, PCB condition and wiring checks recorded.
Technical summary: In this investigation, replacing the ACTPM did not resolve Error 11 and the returned ACTPM was not proven faulty. The factory considered communication between the Main PCB and Inverter PCB to be a more likely area for further investigation.