KMCA / CMCA - IPM & Inverter PCB Replacement Procedure
This article explains the replacement procedure for the inverter PCB / IPM assembly used on selected AOTG KMCA and CMCA outdoor units. The IPM manufacturer and physical IPM size were changed, resulting in a different heatsink screw-hole arrangement. Replacement service parts therefore include the PCB, heatsink, heat paste and replacement procedure.
Important: Before replacing the PCB, identify whether the existing board is Type A (K11BS / SIP IPM) or Type B (K16FY / DIP IPM). Type A requires the heatsink to be replaced. Type B does not require the new heatsink.
Applies To
- AOTG18KMCA
- AOTG22KMCA
- AOTG24KMCA
- AOTG18CMCA
- AOTG24CMCA
Serial Number Cut-In for New IPM
Units from the following serial numbers onward are fitted with the newer IPM arrangement:
| Model | New IPM From Serial Number |
|---|---|
| AOTG18KMCA | E058521 or later |
| AOTG22KMCA | E016415 or later |
| AOTG24KMCA | E101497 or later |
| AOTG18CMCA | E005551 or later |
| AOTG24CMCA | E008646 or later |
Replacement PCB Part Numbers
| Model | Original PCB Part No. | New Assembly Part No. |
|---|---|---|
| AOTG18KMCA | 9709680070 (K11BS-1301HUE-C1-SV) | 9709681466 (K16FY-1601HUE-C1-SV) |
| AOTG22KMCA | 9709680087 (K11BS-1302HUE-C1-SV) | 9709681473 (K16FY-1602HUE-C1-SV) |
| AOTG24KMCA | 9709680094 (K11BS-1303HUE-C1-SV) | 9709681459 (K16FY-1600HUE-C1-SV) |
| AOTG18CMCA | 9709680209 (K11BS-1306WUE-C1-SV) | 9709681480 (K16FY-1603WUE-C1-SV) |
| AOTG24CMCA | 9709680216 (K11BS-1307WUE-C1-SV) | 9709681497 (K16FY-1604WUE-C1-SV) |
New service assembly contents: PCB, heatsink, heat paste and replacement procedure sheet.
Identify the Existing PCB Type
| PCB Type | Identification | Replacement Path |
|---|---|---|
| Type A | PCB name begins K11BS IPM: SIP type Pins on one side | Replace original heatsink, then install new PCB. |
| Type B | PCB name begins K16FY IPM: DIP type Pins on both sides | Do not replace the heatsink. Install the replacement PCB directly. |
Replacement Procedure
- Isolate power to the outdoor unit and confirm the inverter DC bus has discharged before working on the inverter assembly.
- Remove the original inverter PCB from the inverter case.
- Check the PCB identification and determine whether it is Type A (K11BS) or Type B (K16FY).
- Type A only: remove the original heatsink using the hook-release procedure below.
- Type A only: install the new heatsink in the correct orientation and confirm all four retaining hooks are engaged.
- Install the new service PCB into the inverter case.
Removing the Original Heatsink - Type A Only
The heatsink is retained by four hooks: Hook 1, Hook 2, Hook 3 and Hook 4.
- Press the heatsink in the direction shown by the service procedure while releasing Hook 4.
- Release Hook 3 in the same manner.
- From the opposite side, press Hook 2 while pushing the heatsink in the required direction and release Hook 2.
- Release Hook 1 in the same manner.
- Remove the original heatsink from the inverter case.
Caution: Do not force the inverter case or hooks excessively. Release each retaining hook in sequence as shown in the bulletin to avoid damaging the inverter case.
Installing the New Heatsink - Type A Only
- Orient the new heatsink correctly. The side with four holes must face the Hook 1 / Hook 2 side.
- Press the heatsink into Hook 1 and Hook 2.
- Press the opposite side into Hook 3 and Hook 4.
- Confirm the heatsink is securely retained by all four hooks.
Install the Replacement PCB
- Apply the supplied heat paste as required by the replacement assembly.
- Install the new PCB into the inverter case.
- Reconnect all wiring exactly as originally fitted.
- Confirm connectors are fully seated and no wiring is trapped or under strain.
- Complete normal electrical checks before restoring power.
Quick Technician Check
| Check | Requirement |
|---|---|
| Existing PCB | Identify K11BS or K16FY before dismantling heatsink. |
| Type A / K11BS | Replace heatsink and PCB. |
| Type B / K16FY | Reuse existing heatsink; replace PCB only. |
| New heatsink orientation | Four-hole side toward Hook 1 / Hook 2. |
| Heatsink retention | All four hooks fully engaged. |
| Final inspection | All connectors secure, wiring routed correctly and unit checked before energising. |
Source: Service Bulletin RAC-0072, issued 29 August 2016 - "Service work with the IPM change".