General Assist Technical Reference
Active Filter Module Testing
Open / short-circuit, diode and DC output voltage checks
Part No.: 9707278019 | Active Filter Module (AFM)
Purpose: Verify the electrical integrity and output performance of the Active Filter Module, which controls power factor and the DC voltage supply to the outdoor unit inverter circuit.
Electrical safety: Testing includes high-voltage DC circuits. Isolate the unit before resistance or diode testing and confirm the DC bus has discharged before touching terminals. Live voltage measurements must only be carried out by qualified service personnel using suitable test equipment and safe working practices.
1. Open / short-circuit inspection
Procedure
- Disconnect power and remove the connector from the Active Filter Module.
- Using a digital multimeter, check for open or short circuits between the specified terminals.
- Compare the readings with the reference values below.
| Terminal / Check | Tester (+) | Tester (-) | Normal Resistance | Remarks |
|---|---|---|---|---|
| + to N1 | - | N1 | 360 kΩ ± 20% | Normal |
| - to P | + | P | 720 kΩ ± 20% | Normal |
| L1 to L2 | L1 | L2 / Control Box | ∞ Ω | No continuity expected |
| L1 to N2 | L1 | N2 | 1.01 MΩ / 761 kΩ | Within reference |
| L2 to N2 | L2 | N2 | 1.65 MΩ / 1.14 MΩ | Within reference |
| P to N1 | P | N1 | 360 kΩ ± 20% | Normal |
Replace the Active Filter Module if a reading is 0 Ω or significantly deviates from the specified reference value.
2. Diode test (D1)
Measure between L2 and P in both directions. Reference readings can vary depending on the multimeter used.
| Direction | Tester (+) | Tester (-) | Reference Reading |
|---|---|---|---|
| L2 to P | L2 | P | 1.32 MΩ / 663 kΩ |
| P to L2 | P | L2 | 1.01 MΩ / 762 kΩ |
Meter variation: Measurements may vary slightly depending on multimeter type. The source reference lists FLUKE 11 and SANWA PM3 values.
3. Output DC voltage test - P to N1
Procedure
- Measure the DC voltage between P and N1 with the compressor stopped.
- Measure the same voltage again with the compressor operating.
- Compare the two readings. The operating voltage must not be lower than the stopped voltage.
Defective AFM: If the DC voltage measured while the compressor is operating is lower than the voltage measured while it is stopped, replace the Active Filter Module.
4. Quick judgment summary
| Test Item | Terminal(s) | Expected Result | Judgment / Action |
|---|---|---|---|
| Open / Short Circuit | + ↔ N1 | 360 kΩ ± 20% | Replace AFM if reading is 0 Ω or significantly outside reference. |
| Diode Test | L2 ↔ P | Approx. 1 MΩ, with meter-dependent variation | Replace if abnormal. |
| Output Voltage | P ↔ N1 | Stable or higher during compressor operation | Replace if voltage drops under load. |
5. Reference image
Use the terminal identification shown in the service reference when carrying out these checks.
General Assist technical reference — Active Filter Module 9707278019