Aircon Compressor Failed, Confirmed Faulty

Case Details

What We Checked

• Run capacitor tested within 5% of rated value — within range, not the cause.
• Relay contacts were clean and closing correctly — relay ruled out.
• Manual start tried — compressor drew high current and tripped within three seconds.
• Winding tested at all three posts — one phase showed open circuit.

The Diagnosis

One of the three motor windings inside the compressor had developed an open circuit. Over twelve years of thermal cycling — the repeated heating and cooling every time the compressor starts and stops — the insulation on the copper wire gradually breaks down. Once the insulation fails, the winding opens and the motor can no longer create the rotating magnetic field it needs to spin. When we forced a manual start, the remaining two windings tried to carry the full load, which drew excessive current and tripped the thermal protection within seconds. No external component — capacitor, relay, or wiring — can cause an open winding reading. The failure is inside the sealed compressor shell.

What Fixed It

We explained that the winding failure is inside the sealed compressor shell and cannot be repaired on-site. We then presented two clear options with costs for each. Option one was a compressor swap — sourcing a replacement compressor, brazing it into the existing system, vacuuming the circuit, and recharging refrigerant. On a twelve-year-old unit, this is technically possible but expensive, and the rest of the system — capacitors, PCB, expansion valve — has the same age and wear. Option two was a new system. We showed the client the cost comparison side by side and gave an honest view: at this age, the repair cost gets close to new unit cost, and a new system comes with a warranty on every component.

The client chose a new unit after seeing the costs. We wrote up the test results so they had a clear record of what was checked.

Why This Happens

Confirming compressor failure vs. relay or capacitor fault.

• A capacitor or relay fault causes clicking or humming because the compressor tries to start but cannot build enough torque to spin. The motor windings are still intact — it just lacks the electrical push to get moving. These are inexpensive fixes.
• Compressor winding failure looks different: the unit hums briefly then trips on thermal overload, or the outdoor side goes completely silent. The difference is that the motor itself has failed, not the components that help it start.
• The definitive test is a winding resistance check across all three compressor terminal posts. An open circuit reading on any pair means the copper coil inside has broken. No external part — capacitor, relay, or wiring — can produce that reading.
• Ask your technician to show you the meter reading at the compressor terminals. A legitimate diagnosis should include this step. If they condemned the compressor without a winding test, the diagnosis is incomplete.