Compressor Troubleshooting Guide

Properly diagnosing compressor issues is crucial to avoid unnecessary replacements and ensure effective repairs. Follow these steps to troubleshoot both single-phase (1ph) and three-phase (3ph) compressors.

Single-Phase (1ph) Compressor Troubleshooting

Step 1: Resistance Testing (Ohms Test)

1. Get your electrical meter.

2. Set the meter to ohms (resistance mode).

3. Test the windings:

   • Measure between Start (S) and Common (C).

   • Measure between Run (R) and Common (C).

   • Measure between Start (S) and Run (R).

4. Compare your readings:

   • The total resistance from Start to Run should equal the sum of Start to Common and Run to Common.

   Formula:
   S→R=(S→C)+(R→C)

   If this condition is not met, the compressor has an internal winding issue.

Step 2: Grounding Test (Short-to-Ground Test)

1. Measure between each winding and the copper discharge pipe (or an unpainted section of the compressor case).

2. Expected Results:

   • The meter should read OL (open line/infinite resistance) or at least 20 megaohms.

   • If you read continuity (low resistance), the compressor is grounded and must be replaced.

   • Verify also that start capacitor, run capacitor, and potential relay are correct and working properly. Not all compressors will have the start relay and start capacitor.

Three-Phase (3ph) Compressor Troubleshooting

Step 1: Resistance Testing (Ohms Test)

1. Set your meter to ohms.

2. Measure resistance between each pair of windings:

   • Test between L1 - L2, L1 - L3, and L2 - L3.

3. Expected Results:

   • All three readings should be equal or very close in value.

   • Uneven resistance values indicate a damaged winding.

Step 2: Grounding Test (Short-to-Ground Test)

1. Test each winding to the copper discharge pipe (or an unpainted metal surface on the compressor body).

2. Expected Results:

   • The meter should read OL or at least 20 megaohms.

   • If you read continuity (low resistance), the compressor is grounded and must be replaced.

Additional Tips for Accurate Testing

✅ Always isolate the compressor by disconnecting all wiring before testing.
✅ For single-phase units, label wires before removing them to avoid confusion.
✅ Use a reliable digital multimeter with a megaohm scale for precise results.
✅ If readings are inconsistent or borderline, repeat the test to confirm results.

Following these steps will help you accurately diagnose compressor failures and determine whether a replacement is necessary.