When a fridge stops cooling, the compressor is often the first part people blame. In practice, a large share of “compressor” call-outs turn out to be a relay, fan, sensor, control board or defrost fault. Testing properly before replacing anything saves time and money.
This guide explains how a refrigerator compressor is tested, which basic checks are safe for you to do and which steps must be left to a qualified technician.
How to Test a Refrigerator Compressor: The Short Answer
Start with safe checks: listen for the hum and click pattern, feel whether the compressor housing is warm and vibrating, and clean the condenser coils. A full compressor test involves a multimeter check of the windings for resistance and short to earth, testing the start relay and overload, and measuring running current. Those steps involve live electrical parts and should be done by a qualified technician. Refrigerant pressure testing requires an ARC licence.
Safe Checks You Can Do Yourself
1. Listen
A healthy compressor produces a steady, low hum when running. Note what you hear:
- Steady hum and the fridge is cooling: the compressor is probably working.
- Click, brief hum, click again a few minutes later: the compressor is trying to start and the overload is cutting it off.
- Complete silence and a warm fridge: could be the compressor, but also the relay, control board, thermostat or power supply.
2. Feel for warmth and vibration
The compressor is the black, dome-shaped unit at the back bottom of most fridges. Carefully place the back of your hand near the housing. Warm with a slight vibration means it is running. Cold and still means it is not starting. Very hot and cycling off can mean overheating.
3. Clean the condenser and check airflow
Switch the fridge off at the wall, then vacuum dust from the condenser coils and fan. Make sure the fridge has clearance at the back and sides. An overheating compressor sometimes recovers once airflow is restored.
4. Check settings and power
Confirm the fridge is plugged in, the power point works and the temperature setting has not been changed accidentally.
Still not cooling after these checks? Call Ace Fridge Repairs on 0452 462 556 to book a compressor test.
How a Technician Tests the Compressor
The following steps are listed so you understand what happens during a service visit. They involve live components, stored electrical energy and sealed system work, so they are not DIY tasks.
- Check the supply and controls. Confirm the control board or thermostat is actually calling the compressor to run.
- Test the start relay and overload. These inexpensive parts fail often and can stop a healthy compressor from starting.
- Measure winding resistance. With the power isolated, a multimeter is used across the compressor terminals. Readings are compared with the expected values for that compressor.
- Test for a short to earth. Any continuity between the windings and the compressor body means the compressor is unsafe and must be replaced.
- Check running current. A clamp meter shows whether the compressor is drawing the right amount of current while running.
- Test the inverter board where fitted. Many modern fridges drive the compressor with an electronic board. The board can fail while the compressor is fine.
- Check system pressures if needed. If the compressor runs but the fridge will not cool, the technician may check for a refrigerant leak or restriction. This requires an ARC licence.
Do Not Assume It Is the Compressor
These faults cause very similar symptoms:
- faulty start relay or overload
- failed condenser or evaporator fan
- faulty thermostat, sensor or control board
- defrost system failure blocking airflow
- worn door seals making the system work harder
For the full list of warning signs, read our guide on signs of a bad fridge compressor.
Is a Compressor Repair Worth It?
If the fault is a relay, overload or board, repair is usually very worthwhile. If the compressor has failed, the decision depends on the fridge age and condition. Our repair vs replace guide can help.
Compressor Testing and Repairs Across Sydney
Ace Fridge Repairs tests and repairs compressors in household fridges and commercial refrigeration across Greater Sydney from 93B Pagoda Crescent, Quakers Hill NSW 2763. All repairs carry a 12-month warranty on parts and labour. See the suburbs we service.
For residential fridge repairs, call 0452 462 556, 24/7.
Frequently Asked Questions
How can I tell if my fridge compressor is running?
Carefully feel near the compressor housing at the back bottom of the fridge. Warm with a slight vibration and a low hum means it is running. Cold and silent means it is not.
Can I test a fridge compressor with a multimeter myself?
Multimeter testing involves live and stored electrical energy, so it should be done by a qualified technician. You can safely listen, feel for warmth, and clean the condenser coils.
What is the difference between a bad relay and a bad compressor?
Both can cause clicking and no cooling. A relay is a small, inexpensive part and should always be tested before the compressor is condemned.
Can a fridge compressor be repaired, or does it need replacing?
Compressors are sealed units, so internal faults mean replacement. Many problems blamed on the compressor are actually relay, overload or board faults that can be repaired.