What is an open and closed thermostat?
A thermostat is an open and closed switch. They are usually round in shape, like the one shown above, and they open within a set temp range and close within a set temp range. The one shown above is a Carrier Defrost Thermostat, and it closes at 30 degrees +/- 3 degrees and opens at 65 degrees +/- 5 degrees.
How does a defrost thermostat work?
A defrost thermostat is part of a refrigerator. When a defrost cycle begins, the metal alloy switches of the defrost heater are triggered by the timer to switch to warm. When the circuit closes again, it will then cool off the metal. As the thermostat detects this new temperature, it prompts the heater to turn off.
What temperature does a carrier defrost thermostat close at?
The one shown above is a Carrier Defrost Thermostat, and it closes at 30 degrees +/- 3 degrees and opens at 65 degrees +/- 5 degrees. In this case, because this particular sensor closes in colder than 32-degree temps, you can't even use a (freshwater) ice bath to test it.
Why is my freezer not defrosting properly?
However, if after 20 minutes the freezer still has not begun to defrost, then you will need to remove the back wall, and look at the thermostat itself. This should be stuck to the evaporator coil. Turn off your power, and then remove the wiring from the thermostat, and connect them to your defrost heater.
How do I know if my defrost thermostat is working?
2:264:44How To Test Your Defrost Thermostat & How They Work - YouTubeYouTubeStart of suggested clipEnd of suggested clipPlace one of each of the meters probes on each of the defrost thermostat wires while the thermostatMorePlace one of each of the meters probes on each of the defrost thermostat wires while the thermostat is colder than the closing temperature. The thermostat should have continuity.
How do you test a refrigerator defrost thermostat?
Set your multitester to the R X 1 ohms setting. Place each of the multitester's leads on a thermostat wire. When your thermostat is cold, it should produce a reading of zero on your multitester. If it is warm (anywhere from forty to ninety degrees Fahrenheit), then this test should produce a reading of infinity.
What's the purpose of a defrost thermostat?
A defrost thermostat works separately to the refrigeration system and is responsible for stopping frost forming on evaporators, in order to avoid the increased costs of less efficient refrigeration.
What causes a refrigerator to not defrost?
One of the most common reasons your fridge may not be defrosting is a faulty timer. Issues with these parts are easy to diagnose, but the timer itself cannot easily be repaired. The best solution is to replace the timer.
What happens when defrost thermostat fails?
How it fails: The failed defrost thermostat will not accurately sense the temperature around the evaporator coils. So, even when the coils get far too cold while ice and frost continue to build up around them, the thermostat will fail to allow power to flow to the heater.
How does a defrost termination thermostat work?
The function of this temperature-activated switch is to terminate defrost when the evaporator coil has been defrosted, and to delay the evaporator fans from coming on immediately after defrost. Defrost time clocks can be programmed for certain defrost duration periods.
Do freezers automatically defrost?
While most refrigerators, freezers, and refrigerator-freezers on the market today have automatic defrost controls, some models are available with manual defrost. Automatic defrost refrigerators work by heating the interior refrigerator coils at regular intervals.
How do I know if my defrost heater is bad?
0:552:47How To Test A Defrost Heater On A Refrigerator or Freezer - YouTubeYouTubeStart of suggested clipEnd of suggested clipYou should get an approximate reading of 10 to 150 ohms. If the display on the meter does not changeMoreYou should get an approximate reading of 10 to 150 ohms. If the display on the meter does not change or if your own reading is far off for mass then you have a bad email.
How do you reset the defrost button on a refrigerator?
To reset the refrigerator defrost timer, Tepte simply states to locate the circular notch on the timer and turn it counterclockwise with a flathead screwdriver. It needs to be turned until the fan stops, which means your fridge has reset the defrost button.
How to test a heat pump defrost?
Most involve “forcing” a defrost by shorting out pins on the board or advancing the time of the defrost initiation and installing a factory-provided pin jumper. Lots of pins and jumping are involved.
What is a defrost sensor?
A defrost “sensor” is generally a thermistor. A thermistor changes resistance based on the temperature it is exposed to. To test it, you can measure the ambient temperature, make the sensor is removed and acclimated, measure the ohms of resistance, and compare the value to the manufacturer chart.
Can you run a defrost thermostat in heat mode?
Otherwise, you can just run it in heat mode with the outdoor fan off and see when it closes by using an ohmmeter and testing against a line temperature clamp in the same location. On a defrost thermostat, you can also easily jump it out to test the board since it is just open and closed. A defrost “sensor” is generally a thermistor.
Why is the defrost thermostat on my refrigerator important?
The defrost thermostat on your fridge is an important piece of equipment which prevents your freezer from becoming too cold. However, from time to time, these devices can apparently fail, and cause problems which include leaks upon the floor, a warm refrigerator portion, or a freezer section which has ice forming across the back.
How to bypass thermostat on freezer?
Bypass the Thermostat. Turn off your power, and then remove the wiring from the thermostat, and connect them to your defrost heater. This should be easily managed when you are looking at the thermostat, the wires will be evident. Turn the freezer back on, and wait for 10 minutes.
How long does it take for a freezer to defrost?
This should automatically trigger a warming of the freezer section. However, if after 20 minutes the freezer still has not begun to defrost, then you will need to remove the back wall, and look at the thermostat itself.
How to check if thermostat is failing ohms?
Inspect the Connections. Once the thermostat has failed the Ohms test, then you should check the connections at the back. Pry off the connectors, using a pair of thin pliers if necessary, and remove the wires.
How to check temperature on thermostat?
Check the Temp. Open up the thermostat, and find the small vial of mercury that measures the temperature. This can sometimes come out of alignment, and will need to be re-set. Using your pliers, turn the nut on the mercury screw until the connection pops out.
How to check continuity of thermostat?
You should check the voltage continuity of your thermostat, using a multimeter. Connect your probes to the thermostat, and turn it on. When the thermostat has a consistent reading, you should see a Ohms setting of 0.
How does a defrost thermostat work?
Working in conjunction with a timer the defrost thermostat controls the heater which turns on briefly when the bi-metal strip closes the circuit. The duration of the heat cycle is controlled by the timer. This action is not triggered by the frost itself, but rather by the freezer temperature. Even if there is actually no frost present the defrost cycle takes place.
Why is my freezer frost free?
Did you ever wonder why your frost free freezer is indeed frost free? It's because inside every one of these appliances is a heater. This heater melts any frost before it can accumulate and evaporates the moisture away. The little device that makes this possible is the bi-metal, or defrost, thermostat. It is called a bi-metal thermostat ...
What happened before frost free freezers?
In the old days, before frost free freezers, this ice would build up to the point where a freezer door could not be shut. When this happened it was necessary to remove everything from the freezer and melt the ice away. Advertisement.
What is a bi metal thermostat?
It is called a bi-metal thermostat because at its heart is a strip made of two metals with different expansion rates, which when heated begins to curve. This property is used to make a switch which opens with a temperature change.
Where does frost come from?
All that pesky frost comes from the moisture in the air, which condenses out when the air is cooled. The more times the door is opened, especially in the summer time, the greater the potential for frost.
