Maintaining and Troubleshooting Domestic Refrigerators: Chapter 2
Refrigerator Troubleshooting: Secondary Components
In this module, we will discuss the common refrigerator problems associated with secondary components.
We will also learn how to fix these problems. Skip to quiz!
Diagnosing malfunctions
The problems in the refrigerator can occur due to the malfunctioning of secondary components. These include:
Evaporator fan motor, and
Condenser fan motor
Let us go over each of them.
Evaporator Fan Motor
The common problems due to faulty evaporator fan are:
The refrigerator is not cooling
The evaporator fan motor is noisy
The evaporator fan motor does not run at all.
Recall that the evaporator fan blows air across the evaporator coils and through the refrigerator cabinet for cooling. If our refrigerator isn’t cooling well, the fan isn’t running or blowing cool air like usual.
The evaporator fan may fail to run because of:
The faulty electronic control board
Possible broken wires
Faulty fan motor
Let us discuss how to troubleshoot them.
First, test if the evaporator fan runs in the diagnostic test mode. Recall that the instructions for activating diagnostic test mode are available in the tech sheet provided by the manufacturer.
Recall that the control board senses the compressor needs to operate. Then it sends voltage to the compressor and fans to begin the cooling cycle. If the evaporator fan runs in test mode, it means the faulty control board is not sending voltage to the fan.
We need to replace the faulty control board. Let us look at the video that shows steps to replace the control board.
To replace the control board remove the screw that holds the control box. Remove the control board wiring harness. Connect the wires to the new control board and mount the control box in place.
If the evaporator fan doesn't run in the diagnostic test mode, check for a break in the wiring. Remove the screw that holds the control box and lower the control box. Check the wire for visible damage. Repair the wire if it's pinched or broken.
If the wire isn’t visibly damaged, check for electrical continuity in the wires supplying power to the fan. Put a multimeter lead on the wire going to the fan and control board. If the wire is intact, the multimeter reads near 0 ohms. Check the light blue wire in the same way.
If both wires have continuity, the problem is with the fan motor or the electronic control board. If neither wire has continuity, then we should look for pinched or broken wires.
If there is no issue with the wiring and control board, we must check the evaporator fan motor. The evaporator fan motor has a control board inside the motor casing, so you can’t check for continuity. Instead, remove the support bracket and fan motor cover to examine the fan control board for damage.
We need to replace the evaporator fan motor if the board has visible burn marks. If you don’t see any damage, test the evaporator fan.
For testing the evaporator fan, put the multimeter on the Ω setting. Connect the multimeter lead to two wires of the evaporator fan. If the multimeter reads resistance in the range of 10 Ω to 100 Ω, the evaporator fan is working fine. Let us look at the video that shows this.
If the multimeter reads less than 10 Ω resistance, we should replace the evaporator fan motor. Let us look at the video that shows how to replace the evaporator fan motor.
We need to push the evaporator fan cover up and pull the fan blade off the motor shaft. Then, lift the motor out of the mounting bracket. We then insert the new fan motor in the mounting bracket. The next video shows stepwise troubleshooting of the fan.
Condenser Fan Motor
The complaints associated with the failure of the condenser fan motor are:
The refrigerator temperature is warm.
The condenser fan motor does not run at all.
Noisy fan motor
Much like an evaporator fan, the condenser fan may fail to run because of:
A faulty electronic control board
Possible broken wires
Faulty fan motor
We will have to troubleshoot these issues the same way.
If there is no problem with the control board and wiring, we need to replace the fan motor. Let us look at the video that shows how to replace the fan motor.
We need to pull the fridge away from the wall. Then, we should remove the thin panel on the back near the bottom to access the condenser fan.
Next, we should remove the wires connected to the old fan. Connect the new fan with wire connectors. Screw the new fan to the bracket and reinstall the fan and bracket in the fridge.
The evaporator fan and condenser fan may fail to run because of:
A faulty electronic control board
Possible broken wires
Faulty fan motor
We troubleshoot these components to keep the refrigerator cool.
Refrigerator Troubleshooting: Defrost System - Part 1
In this module, we will discuss the common refrigerator problem associated with defrost system.
We will also learn how to fix these problems. Skip to quiz!
Diagnosing malfunctions
The most common problems due to faulty defrost system in our refrigerator are:
The refrigerator/freezer does not defrost
The freezer is cool, but fridge stays warm
The reasons behind the refrigerator defrost problem are:
Defective defrost heater
Defective defrost thermistor
Defective thermostat
Faulty defrost timer
Let us take a look at how to troubleshoot each of them.
Defrost Heater
Recall that a defrost heater melts the frost developed over the evaporator coil. To troubleshoot the heater first, check if it turns on when in diagnostic test mode.
We should check whether the frost starts to melt in the test mode. If the frost melts in the test mode, the heater is working fine. Unplug the refrigerator to exit the test mode.
If the defrost heater doesn't work in the test mode, check for continuity through the defrost heater circuit. For checking the continuity of the circuit, the refrigerator temperature should be below 46℃.
We need to remove the control panel down to access the electronic control board. Then, check the defrost heater circuit by putting multimeter leads on the wires connected to the control board. Let us look at the video that shows how to troubleshoot the defrost heater.
The circuit has continuity if the multimeter reads about 10 to 150 ohms. If the circuit has continuity, then defrost heater is working fine.
If the defrost heater circuit does not have continuity, then defrost heater is faulty. We need to replace the faulty defrost heater. Let us look at the video that shows how to replace a faulty defrost heater.
We need to remove the mounting screws from the evaporator cover to access the defrost heater. Disconnect wiring harness connected to defrost heater. We should slide the defrost heater out and insert a new defrost heater back up under the evaporator.
Defrost Thermistor
Recall that the defrost thermistor sends a signal to the control board to control the defrost heater during the automatic defrost cycle. If the heater is working fine, there might be a problem with the thermistor or control board.
If the defrost thermistor fails, the control board won't control the defrost heating element correctly. Let us look at the video that shows how to test a defrost thermistor.
We need to remove the temperature sensor from the refrigerator. Grab the evaporator panel, pull it. Then, disconnect the wiring harness by depressing the locking clip and pulling it out. Next, remove the sensor from the refrigerator.
We need to visually inspect the temperature sensor for any cracks, breaks in the wires. For testing the temperature sensor, we will need a multimeter that can measure at least 20,000 ohms.
The refrigerator service manual contains a chart representing the relationship between temperature, resistance, and voltage. The image to the right shows the Temperature-Resistance-Voltage chart for the refrigerator sensor. This table gives exact resistance at a particular temperature for working sensor.
The temperature sensor is tested at two different temperature levels: One at room temperature and one in a glass of ice water. To test the temperature sensor, touch each of the two probes to each of the two wires of the temperature sensor.
Our room temperature is approximately 77℉. So, our multimeter reading should be in the range of 5000 ohms. If it is not in the range specified on the chart, then the sensor is faulty.
We should insert our temperature sensor into a glass of ice water to test it for other temperatures. With our cup of ice water just above 32℉, we should get a multimeter reading in the range of 13000 ohms. If it doesn't fall in the given range, we should replace it. Let us look at the video of this.
The most common problems due to faulty defrost system in our refrigerator are:
The refrigerator/freezer does not defrost
The freezer is cool, but fridge stays warm
The reasons behind the refrigerator defrost problem are:
Defective defrost heater
Faulty defrost thermistor
Defective thermostat
Faulty defrost timer
We will go over troubleshooting of thermostat and timer in the next topic.
Refrigerator Troubleshooting: Defrost System - Part 2
In this module, we will discuss the common refrigerator problem associated with defrost system.
We will also learn how to fix these problems. Skip to quiz!
Defrost Thermostat
Recall that defrost thermostat sends a signal to the control board during the automatic defrost cycle to terminate the defrost cycle. If we didn't get continuity through the heater circuit, there might be a defective bi-metal thermostat. Let us look at the video that shows troubleshooting of the thermostat.
To test our defrost thermostat, we will need to unplug the refrigerator and disconnect the wires to the thermostat. If the thermostat has continuity, it will function properly. If there is no continuity means the electrical path is broken and the thermostat has failed.
We need to set the multimeter dial to the Ω setting. Since a temperature change activates the thermostat, we need to place it in a glass of ice water for one or two minutes.
We should connect the multimeter probe to one of the thermostat terminals and the second probe to another terminal. If the multimeter reading shows zero ohms of resistance, the thermostat has continuity.
There is no continuity if the multimeter reading shows OL or 1 in the far left digit. This means the thermostat has failed and will need to be replaced. Let us look at the video that shows how to replace the defrost thermostat.
We need to remove the mounting screws from the evaporator cover. Then, we need to pull the cover out of the freezer. Unplug the wires from the defrost heater and release the defrost bi-metal thermostat from the evaporator coils.
Then, we should connect the new bi-metal thermostat to the supply wires using the wire connectors. We then attach the defrost bi-metal thermostat to the evaporator. Put the evaporator cover in position and reinstall the mounting screws.
Defrost Timer
Recall that defrost timer has four pins labeled from 1 to 4. The main input power is attached to pin 1. When pin 1 connects to pin 2, the timer turns off the compressor, and defrost cycle begins.
When the timer is not in defrost mode, pin 1 connects to pin 4, which activates the compressor and fan. Pin 3 is our ground. For troubleshooting the timer, we should check continuity across these pins. Let us look at the video that shows how to test the defrost timer.
For the cooling cycle, we should get continuity between pin 1 and pin 4. This is because when the timer is not in defrost mode, pin 1 connects to pin 4. If we do not get continuity, there may be a problem with defrost timer.
We need to rotate the manual dial on the defrost timer to put it into the defrost mode. Then put the multimeter lead on pin 1 and pin 2 to check continuity.
If we have continuity between pin 1 and 2, it means the timer activates defrost cycle. This is because in the defrost mode, pins 1 and 2 get connected. If we do not get the continuity, we need to replace the timer. Let us look at the video that shows this.
Remove the screws that secure the timer to the refrigerator. Remove the wires connected to the timer and take out the old-timer.
Then, we need to reattach the wiring to the time. We then secure the timer back to the refrigerator with screws.
When pin 1 connects to pin 2, the timer turns off the compressor, and defrost cycle begins. When the timer is not in defrost mode, pin 1 connects to pin 4, which activates the compressor and fan. We check continuity across these pins in both the mode to troubleshoot the timer.
If the multimeter reading shows zero ohms of resistance, the thermostat has continuity. If there is no continuity if the multimeter reading shows OL or 1 in the far left digit and the thermostat is defective.
Question #1: Why does the refrigerator evaporator fan fail to run? (select all that apply)
Faulty electronic control board
Faulty thermistor
Faulty defrost heater
Faulty fan motor
Scroll down for the answer...
Answer: Faulty electronic control board
Faulty fan motor
The evaporator fan may fail to run because of:
The faulty electronic control board
Possible broken wires
Faulty fan motor
Question #2: If the wire is pinched or broken, there will be no electrical continuity in the circuit.
True
False
Scroll down for the answer...
Answer: True
True.
If the wire isn’t visibly damaged, or broken the circuit is not continuous. We need to check for the electrical continuity of such wire using a multimeter.
Question #3: Why does the refrigerator condenser fan fail to run? (select all that apply)
Faulty electronic control board
Faulty thermistor
Faulty defrost heater
Faulty fan motor
Scroll down for the answer...
Answer: Faulty electronic control board
Faulty fan motor
The condenser fan may fail to run because of:
The faulty electronic control board
Possible broken wires
Faulty fan motor
Question #4: What is the reason behind the faulty defrost system of the refrigerator? (select all that apply)
Defective thermostat
Defective ice bucket auger
Defective defrost heater
Defective door sensor
Scroll down for the answer...
Answer: Defective thermostat
Defective defrost heater
The reasons behind the refrigerator defrost problem are:
Faulty defrost timer
Defective defrost heater
Defective thermostat
Question #5: How do we troubleshoot defrost heater of the refrigerator?
By measuring heating time
By checking continuity of the defrost circuit
By checking heater color
By checking heater temperature
Scroll down for the answer...
Answer: By checking continuity of the defrost circuit
We check the continuity of the defrost circuit to troubleshoot the defrost heater. If the circuit has continuity, then defrost heater is working fine.
Question #6: What resistance value should the multimeter display for the functioning thermistor of the refrigerator?
Less than 100 ohms
A value corresponding to the temperature resistance chart
Infinite
Less than 10 ohms
Scroll down for the answer...
Answer: A value corresponding to the temperature resistance chart
We should get a resistance value corresponding to the temperature resistance chart on the multimeter for a particular temperature.
Question #7: How do we know there is no continuity in the defrost thermostat of the refrigerator?
Multimeter reading shows more than 100 ohms
Multimeter reading shows 10 ohms to 100 ohms
Multimeter reading shows OL or 1
Multimeter reading shows 10 ohms
Scroll down for the answer...
Answer: Multimeter reading shows OL or 1
If the multimeter reading shows OL or 1 in the far left digit, then there is no continuity in the defrost thermostat of the refrigerator.
Question #8: The defrost timer should show continuity between pins 1 and 2 for a cooling mode of the refrigerator.
True
False
Scroll down for the answer...
Answer: False
False.
The defrost timer should show continuity between pins 1 and 2 for a defrost mode of the refrigerator.