Single Phase Compressor Winding Test Guide

This guide applies to single-phase domestic compressors that have a Starter, PTC and Capacitor.

If the compressor is not running, this test will determine if the compressor is faulty from an electrical aspect.

DISCONNECT ALL POWER FROM THE FRIDGE BEFORE WORKING!

On a typical compressor, you will notice a connector. The image above indicates the connectors and what they mean. It also shows the winding configuration inside the compressor.

C(Common) is the common line which can either be Live or Neutral.

S(Start) is the Starting winding which helps to start turning the compressor. This builds up the torque due to the high pressure of refrigerant in the system.

R(Run) is the Running Winding which powers up once the compressor has started turning.

Testing for Earth Leakage

Typically an earth fault can occur where the winding insulation has deteriorated. This causes an “Earth Leak” between the winding and the chassis of the compressor. When this occurs, the breakers usually trip.

There have been many instances where the earth has been completely removed if there is an earth leak. This will KILL SOMEONE!

If there is an earth leak, replace the compressor IMMEDIATELY.

Performing the Earth Leak Test

Ensure that the power for the fridge is disconnected first!

1. Remove the starter and the PTC from the compressor.
2. You will need a multi-meter set on OHM.
3. Place one probe of the multi-meter on the metal chassis of the compressor, making sure it has good contact.
4. With the other probe, touch the C, S and R terminals one at a time.
   1. If there is an Ohm Reading, then there is an earth leak, in which case, replace the compressor.
   2. If there is no reading, then the compressor has passed the earth-test.

Testing the windings

Sometimes the windings need to be checked in order to test if there is an electrical fault.

The windings between C, S and R need to be calculated.

Performing the winding test

Ensure that the power for the fridge is disconnected first!

1. Remove the starter and the PTC from the compressor.
2. You will need a multi-meter set on OHM.
3. Place one probe of the multi-meter on the “C” terminal.
   1. Test the Start winding by placing the other probe on the S. Write the Ohm reading down.
   2. Test the Run winding by placing the probe on the R. Write the Ohm reading down.
4. Test the S and R windings by placing one probe on the S and the other on the R.
5. Add the reading from C to S and C to R. The sum should equal the reading from S to R.

If there is no reading on either of the tests, this means the winding has burnt out, in which case, the compressor will need to be replaced.

Compressor Component Test Guide #1

This guide applies to single phase domestic compressors that have a Starter, PTC and Capacitor.

Often the starting components can fail and will need replacing. To ensure that these components are functioning, follow this guide.

DISCONNECT ALL POWER FROM THE FRIDGE BEFORE WORKING!

Testing the capacitor

Remove starter, PTC and capacitor from the compressor.

Discharge the capacitor by shorting out the capacitor terminals. A small arc should occur if there is charge in the capacitor. Do this regardless in order to safe-guard your test instrument and to prevent an inconvenient shock.

You will need a multi-meter that can test Farads.

Test the capacitor Farads with the instrument. The reading should be within 10% of the Farad reading shown on the capacitor. If there is no reading on the instrument, replace the capacitor with an equivalent type.

Testing if the compressor or if the starter is faulty

Sometimes you will need to test if the compressor is indeed faulty or if the starting components are at fault.

This test can also help to “jump-start” a compressor which is stuck.

DISCONNECT ALL POWER FROM THE FRIDGE BEFORE WORKING!

Remove the starter, PTC and the capacitor from the compressor.

Using the diagram below, create a “jump-starter” to test if the compressor or the starting equipment is faulty.

If the compressor runs with this test, then the start and PTC will need to be replaced.

This test should be done only for a few seconds.

Thermostat Test Guide

This guide has a step-by-step guide to test mechanical thermostats (Non digital).

A three wired thermostat has Power, Motor and Defrost Heater/Solenoid terminals.

A two wired thermostat has Power and Motor terminals only.

Before continuing ensure that the power to the fridge is off.

• Locate the thermostat and take note of the wiring colours on the thermostat.
• Disconnect all the wires from the thermostat.
• Turn the thermostat clockwise. This is the maximum “warm” setting.
• Set your multimeter to “Ohm” setting.
• Place one probe on the “power” terminal and the other probe on the “motor” terminal. 
• You should see a reading on your meter. If there is no reading, turn the thermostat dial in the opposite direction. If you still do not have a reading, replace the thermostat.