Overview
The Intelligent Power Module (IPM) — also referred to as the TR PCB — is a key inverter board component responsible for switching and driving the compressor motor. It regulates the DC to AC conversion required for variable-speed compressor operation.
This diagnostic procedure is used to confirm the integrity of the IPM’s internal transistors and diodes.
Safety Warning
⚠️ High Voltage Hazard
Always isolate power and discharge capacitors before testing.
Failure to do so may result in electric shock or permanent PCB damage.
Testing Conditions
Power must be OFF and isolated.
Disconnect all control harnesses and the compressor terminal harness (U, V, W) before measurement.
Use a digital multimeter set to Diode Test Mode.
Procedure
Identify the terminal layout on the IPM board:
U, V, W – Compressor output phases
P – Positive DC bus
N – Negative DC bus
(Refer to board diagram for terminal locations.)
Place the black test lead on the P terminal.
Measure to U, V, and W terminals using the red test lead.
Expected reading: 0.4 V for each terminal.
Place the red test lead on the N terminal.
Measure to U, V, and W terminals using the black test lead.
Expected reading: 0.4 V for each terminal.
Measure between P and N terminals.
Black to P / Red to N: 0.7 – 0.9 V
Black to N / Red to P: Open circuit (O/L)
Reference Values
| BLACK LEAD | RED LEAD | EXPECTED VALUE |
|---|---|---|
| P → U | 0.4 V | |
| P → V | 0.4 V | |
| P → W | 0.4 V | |
| U → N | 0.4 V | |
| V → N | 0.4 V | |
| W → N | 0.4 V | |
| P → N | 0.7 – 0.9 V | |
| N → P | O/L |
Diagnosis and Interpretation
| Observation | Diagnosis | Recommended Action |
|---|---|---|
| Readings within specification | Normal operation | No action required |
| 0 V across all measurements | IPM short circuit | Replace IPM board |
| O/L (Open) on all readings | Internal transistor open circuit | Replace IPM board |
| Low or inconsistent readings | Partial short or leakage | Replace IPM board |
| Fuse or breaker trips during power-up | Internal IPM fault or DC bus short | Replace IPM and inspect power board |
Technical Notes
Always confirm ACTPM and power supply boards are functioning correctly before replacing the IPM.
If replacing the IPM, apply fresh thermal compound between the module and heat sink.
Ensure all electrical connectors are clean, tight, and moisture-free.
