To troubleshoot a compressor in a Refrigerator or Freezer, it’s essential to understand how it functions and the typical signs of failure. Here’s a detailed guide to diagnosing and potentially resolving compressor-related issues:
1. Listen for Unusual Noises
- Normal Compressor Sound: When working properly, the compressor will produce a low, steady hum or buzz. Occasional clicks may also be heard as it cycles on and off.
- Signs of Trouble:
o Loud Humming or Buzzing: Could indicate the compressor is trying to start but can't.
o Clicking: Repeated clicking could mean the compressor is trying to start, but it's either overheating or the
relay is failing.
o No Sound: If the compressor is completely silent when the freezer should be cooling, it may indicate a
failure.
2. Check Compressor Temperature
- Touch Test: Carefully touch the compressor’s surface (use caution as it may be hot).
o Too Hot to Touch: A compressor that’s excessively hot may be overheating due to overwork or
malfunction. It could also point to problems with the start relay or capacitor, preventing the compressor
from functioning efficiently.
o No Heat: If the compressor isn’t warm at all, it may not be running.
3. Test the Start Relay
- The start relay helps the compressor kick into gear. If the relay is defective, the compressor won't start.
o Procedure:
1. Unplug the Freezer: Always start by cutting off power to the unit.
2. Locate the Start Relay: It’s usually mounted on the side of the compressor.
3. Shake Test: Remove the start relay and gently shake it. If you hear a rattling sound, it’s likely
burned out.
4. Multimeter Test: Use a multimeter to test the relay’s continuity. If there’s no continuity, it’s
defective and needs replacing.
4. Inspect the Capacitor
- The start capacitor provides the extra boost of power the compressor needs to start.
o Signs of Failure: If the capacitor is defective, the compressor may not start at all, or you may hear a
humming noise.
o Testing the Capacitor:
1. Unplug the Freezer.
2. Locate the Capacitor: It’s usually near the start relay.
3. Discharge the Capacitor: Use a screwdriver to discharge any stored energy (be careful when
handling capacitors).
4. Multimeter Test: Switch your multimeter to capacitance mode and connect its probes to the
capacitor’s terminals. The polarity of the probes is not important for this test. Compare the
multimeter’s reading with the capacitor’s printed value. A good capacitor’s measured capacitance
should fall within the manufacturer’s specified range. A significant deviation from this range
indicates a malfunctioning capacitor that likely needs replacement.
5. Set the multimeter to the ohm (Ω) setting and test the capacitor. A good capacitor should
gradually show increasing resistance. If it shows no reading or zero resistance, it’s faulty and
needs replacement.
5. Check the Overload Protector
- The overload protector cuts off power to the compressor if it overheats or draws too much current.
o Testing Procedure:
1. Unplug the Freezer.
2. Locate the Overload Protector: It’s typically attached to the start relay or compressor.
3. Multimeter Test: Test for continuity using a multimeter. If there’s no continuity, the overload
protector has failed and will need to be replaced.
6. Check for Refrigerant Issues
- Refrigerant Low/Leaks: If there’s a leak, the compressor will run continuously without cooling effectively.
However, refrigerant-related issues typically require professional attention due to the specialized tools needed for
detection and repair.
• Signs of a Leak:
o Compressor runs constantly but the device doesn’t reach the set point.
o Ice buildup in certain areas.
o Hissing or bubbling noises near the evaporator coils.
7. Compressor Running But No Cooling
- Blocked Refrigerant Lines: If the compressor is running but no cooling is happening, there may be a blockage in the refrigerant lines, restricting the flow of refrigerant. This requires a professional to flush or replace the lines.
- Internal Compressor Failure: If the internal mechanisms of the compressor (e.g., motor windings, valves) are
damaged, it will need to be replaced. Testing the windings with a multimeter can confirm this, but it’s a
complicated process that often requires a technician.
8. Final Step: Replacing the Compressor
- If the compressor itself has failed (e.g., due to internal damage, seizing), replacing it is a major repair.
Compressor replacement requires:
o Evacuating the refrigerant from the system.
o Replacing the compressor.
o Recharging the system with the correct amount of refrigerant.
o Testing for leaks and proper operation. - Note: Compressor replacement is generally a job for a licensed refrigeration technician.
Conclusion
If the compressor is noisy, running hot, or not running at all, start by checking the simpler components like the start relay, capacitor, and overload protector. If these seem to be functioning, you may need to call a professional for deeper troubleshooting, refrigerant checks, or compressor replacement.
To test and troubleshoot the compressor in detail, here’s how you can proceed, focusing on diagnosing the issue, checking key components, and potentially repairing or replacing the compressor.
Step 1: Prepare for Testing
Before working on the compressor, follow these safety steps:
- Unplug the Freezer: Always disconnect the freezer from the power source to avoid electrical hazards.
- Gather Tools: You’ll need a multimeter, a screwdriver, and a socket wrench if you need to remove parts like the compressor cover.
Step 2: Locate the Compressor
The compressor is typically located at the back or bottom of the freezer. It’s a sealed metal unit, usually black or silver, and about the size of a football.
- Remove the Access Panel: If necessary, use a screwdriver to take off the panel at the back or bottom of the
freezer to expose the compressor and associated components (start relay, capacitor, and overload protector).
Step 3: Inspect the Compressor for Physical Issues
Before testing the electrical components, perform a quick visual check:
- Check for Oil Leaks: Any oil around the compressor indicates a refrigerant leak.
- Burn Marks: Inspect for any burnt wires or components around the compressor.
Step 4: Testing the Compressor’s Electrical Components
To determine whether the compressor is functioning properly, test the following components:
1. Test the Start Relay
The start relay helps the compressor start. A faulty relay can prevent the compressor from running.
- Locate the Start Relay: It’s attached to the side of the compressor, usually in a small plastic housing.
- Remove the Relay: Pull the relay off the compressor. Be gentle to avoid damaging it.
- Shake Test: Shake the relay gently. If you hear rattling or loose parts inside, the relay is likely faulty.
- Multimeter Test:
1. Set the multimeter to the lowest ohm setting (continuity test).
2. Place one probe on the terminal leading to the compressor and the other on the terminal leading to the
capacitor. A working relay should show continuity. If not, replace the relay.
2. Test the Start Capacitor
The capacitor gives the compressor an electrical boost to start. If this component fails, the compressor may hum but won’t start.
- Discharge the Capacitor: Capacitors store electrical charge, so carefully discharge it by shorting the terminals with a screwdriver with an insulated handle.
- Multimeter Test:
1. Set the multimeter to the capacitance setting (labeled as "µF").
2. Place the multimeter probes on the capacitor terminals.
3. Compare the reading to the capacitor's rated value (written on the capacitor). If the reading is significantly
lower or shows zero, the capacitor is faulty and needs to be replaced.
3. Test the Overload Protector
The overload protector shuts down the compressor if it overheats or draws too much current.
- Locate the Overload Protector: It’s often mounted on or near the start relay.
- Multimeter Test:
1. Set the multimeter to continuity mode.
2. Place one probe on each terminal of the overload protector. There should be continuity (low resistance). If
there’s no continuity, the overload protector has failed and needs replacement.
Step 5: Testing the Compressor Windings
The compressor has internal windings (start, run, and common windings) that you can test with a multimeter. If these windings are damaged, the compressor will need to be replaced.
1. Identify the Compressor Terminals
You will see three metal prongs sticking out from the side of the compressor. These are the electrical terminals labeled as:
- C (Common)
- S (Start)
- R (Run)
2. Set Up the Multimeter
- Set your multimeter to the ohms (Ω) setting to measure resistance.
3. Test the Windings
- Between C and S (Start): Place one probe on the common terminal (C) and the other on the start terminal (S). Record the reading.
- Between C and R (Run): Place one probe on the common terminal (C) and the other on the run terminal (R).
Record the reading. - Between S and R (Start and Run): Place the probes on the start (S) and run (R) terminals. Record the reading.
4. Analyze the Results
- Reading Interpretation:
o The sum of the resistance between C and S plus C and R should roughly equal the reading between S
and R.
o If the readings are way off or show no continuity (infinite resistance), the compressor windings are likely
damaged, and the compressor will need to be replaced.
Step 6: Check for Ground Faults
Sometimes the compressor can short to the ground, which can cause it to fail or trip breakers.
- Multimeter Test:
1. Set the multimeter to the continuity setting.
2. Place one probe on a compressor terminal (C, S, or R) and the other probe on the compressor’s metal
casing.
3. If you detect continuity, the compressor is grounded, which indicates an internal short, and the
compressor will need to be replaced.
Step 7: Conclusion and Repair
After running these tests:
- If the Start Relay, Capacitor, or Overload Protector are Faulty: Replace the faulty component. Many of these
parts are relatively inexpensive and easy to replace without needing a professional. - If the Compressor Windings are Damaged or it’s Grounded: The compressor itself has likely failed. In this
case, you will need to replace the entire compressor. This is a more complex job that typically requires a
professional technician.
Compressor replacement involves:
- Recovering the refrigerant.
- Disconnecting the compressor.
- Installing a new compressor.
- Recharging the system with refrigerant.
Replacing a compressor in Freezer is a complex task that involves handling refrigerant, electrical components, and sealed systems. It’s highly recommended to involve a certified refrigeration technician due to safety concerns and the need for specialized tools (e.g., a refrigerant recovery machine, vacuum pump, etc.). However, if you’re familiar with refrigeration systems and want a general guide, here’s how the process works:
Tools and Materials Needed
- Replacement compressor (ensure it matches the specifications of the old one)
- Refrigerant recovery machine (to safely remove the old refrigerant)
- Vacuum pump (to remove air and moisture from the system)
- Brazing torch (for copper pipe connections)
- Pipe cutter
- Refrigerant (ensure you have the right type for your system, e.g., R290A or another low-temperature refrigerant)
- Filter/drier (replace this when changing the compressor)
- Manifold gauges and hoses (for refrigerant charging and recovery)
- Nitrogen tank (for leak testing and cleaning)
- Multimeter
- Safety gear (gloves, goggles, etc.)
Step-by-Step Guide to Replacing a Compressor
1. Recover the Refrigerant
Before starting, ensure that the freezer is unplugged and that the refrigerant is safely recovered from the system.
- Connect the Refrigerant Recovery Machine: Attach the manifold gauges to the system’s high and low-pressure service ports and connect the recovery machine.
- Recover the Refrigerant: Follow the recovery machine’s instructions to remove all the refrigerant from the
system and store it in a recovery tank. - Verify the System is Depressurized: Check the manifold gauges to confirm that no pressure remains in the
system.
2. Disconnect the Old Compressor
Now that the refrigerant is safely removed, you can disconnect the compressor.
- Disconnect Electrical Wiring: Carefully remove the electrical connections to the compressor, including wires for the start relay, capacitor, and overload protector.
- Cut the Refrigerant Lines: Use a pipe cutter to cut the refrigerant lines connected to the compressor (usually two copper lines: one for the suction side and one for the discharge side). Leave enough length for re-brazing the new compressor.
- Remove the Compressor Mounting Bolts: Use a socket wrench to remove the bolts holding the compressor in place.
- Remove the Compressor: Carefully lift out the old compressor and set it aside for proper disposal.
3. Prepare and Install the New Compressor
With the old compressor removed, you can now install the new one.
- Position the New Compressor: Place the new compressor in the same location and secure it with mounting
bolts. - Clean the Refrigerant Lines: Use nitrogen to blow through the lines and remove any debris or dirt