Question about Refrigerators

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Cooling coils in freezer icing up

I believe the defrost timer or heater not working. How do I determine which one it is

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  • captainb6 Jun 05, 2009

    How can I test the heater? if I remove it can I apply 110 current to test or is there an ohm value I could test for. How can I test the timer?



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Testing the defrost timer:

The first thing you will have to do is turn off the breaker that supplies power to the refrigerator or unplug it from the wall outlet. Either way will suffice, as long as you do not try working on your refrigerator while it is powered.

Find the defrost timer. Depending on the make and model of your refrigerator, it may be found in one of the following areas:

Behind the front grill in the freezer
Behind the cover plate in the freezer
Behind the freezer near the compressor
Inside the temperature control console

Once you locate the defrost timer, look on the timer and find the advance screw. Turn it clockwise until you hear it click. Turn the power back on to the refrigerator. If the refrigerator was stuck in cool mode previously, this will advance it into defrost mode. Wait for about 30 to 40 minutes and then check it again to see if it advances back into the cooling mode. You will know when it begins cooling again, as the compressor will turn on.

If after 30 to 40 minutes you discover that the defrost timer is not advancing, then turn the power off to the refrigerator and remove the timer. The plug that connects to the timer can only be connected one way, so it's not important to draw a wiring schematic for this job.

If the timer did advance as it was designed to do, then you will now have to test the timer electronically. With the power off to the refrigerator, remove the defrost timer. Take the timer to a clean workspace.

Set your multitester to read ohms. This is usually the RX1 or X1 setting depending on the model of tester. If you look at the defrost timer, there should be four terminals. Find the terminal that is labeled "C" or "3." If the timer is not labeled, look at the connector plug to determine which terminal gets connected to the white wire; that is the common terminal.

Touch one of your tester's probes to the common terminal. Then, touch the other probe to each of the remaining terminals on the timer. As you touch the other terminals, one or two of the terminals (depending on the timer's current setting) should read "zero" and the remaining one or two should read "infinity."

Turn the advance screw again until you hear the click and then reprobe the terminals. This time, the results should be reversed. The terminal(s) that read "zero" earlier should now read "infinity" and the other(s) should now read "zero." It the timer does not pass this test, then it should be replaced. If it does operate correctly, then return it to its position in the refrigerator. The problem with your refrigerator may be caused by another issue like a bad defrost heater or thermostat.


Before you begin to test your defrost heater, make sure you disconnect the appliance's power supply. The easiest way to do this is to unplug the unit from the wall. Alternatively, you could trip the appropriate switch in the circuit breaker panel, or you could remove the appropriate fuse from your home's fuse box.

Consult with an appliance repair technician if you do not feel you have the skill or the ability to successfully complete this repair.

  1. Locate your defrost heater. It can be located behind the back panel of the freezer section of your refrigerator, or under the floor of your refrigerator's freezer section. Defrost heaters are commonly located beneath a refrigerator's evaporator coils. You will have to remove any objects that are in your way such as the contents of the freezer, freezer shelves, icemaker parts, and the inside rear, back, or bottom panel.

  2. The panel you need to remove may be held in place with either retainer clips or screws. Remove the screws or use a screwdriver to release the clips holding the panel in place. Some older refrigerators may require that you remove a plastic molding before you can gain access to the freezer floor. Exercise caution when removing the molding, as it does break fairly easily. You could try warming it with a warm, wet towel first.

  3. Defrost heaters are available in one of three primary types: exposed metal rod, metal rod covered with aluminum tape, or a wire coil inside a glass tube. Each of these three types is tested in exactly the same way.

  4. Before you can test your defrost heater, you have to remove it from your refrigerator. A defrost heater is connected by two wires, and the wires are connected with slip-on connectors. Firmly grasp these connectors and pull them off the terminals. You may need a pair of needle-nosed pliers to help you. Do not pull on the wires themselves.

  5. Use your multitester to test the heater for continuity. Set your multitester to the R X 1 scale. Place the tester's leads on one terminal each. This should produce a reading anywhere in between zero and infinity. If your multitester produces a reading of zero, or a reading of infinity, then your defrost heater should most definitely be replaced. There are many different kinds of elements, and so it is difficult to say what exactly the reading should be for your defrost heater. But it definitely should not be zero or infinity. If it is, replace the mechanism.

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Posted on Jun 05, 2009

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Its probably the heater.

Have a look at this HVAC refrigerator repair video I saw on youtube few days ago, in that case the heater is faulty and you can clearly see it on the video.

So check the heater if it looks good and heats then its not the problem and its the timer most likely. if its obviously faulty as you see on the video then replace the heater.

Posted on Jun 04, 2009


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The refrigerator is supposed to self-defrost approximately four times in every 24 hour period. If one of the components in the self-defrosting system fails, the refrigerator continues to try to cool. Eventually, though, so much frost builds up on the evaporator coils that the circulating fan can't draw air over the coils. There may still be a small amount of cooling because the coils are icy, but with no air flow over the coils, cooling in the refrigerator compartment is quite limited. Poor cooling is often the result of a heavy frost build-up on the evaporator coils. You can't see these coils without removing a panel on the inside of your freezer. A sure sign that there is a build-up is the presence of any frost or ice build-up on the inside walls, floor, or ceiling of the freezer. Such a frost build-up usually indicates a problem in the self-defrosting system or damaged door gaskets.Here's an inexpensive, though inconvenient, way to determine if the problem is with the self-defrosting system. Remove all of the perishable food from the refrigerator and freezer, turn the thermostat in the refrigerator to Off, and leave the doors open for 24 to 48 hours. (Be sure to have several towels ready in case the melting frost and ice causes the drip pan to overflow). This allows the refrigerator to defrost "manually." When the frost and ice build-up has completely melted away, turn the thermostat back to a normal setting. If the refrigerator then cools properly, it indicates a problem with one of three components in the self-defrosting system: The defrost timer The defrost thermostat (also called the bi-metal switch) The defrost heater. To determine if the defrost heater is burned out, watch this part testing video

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If / when you do call for service, having the freezer emptied & defrosted already - will save the cost of defrosting time by the repair person.

I hope this was helpful and good luck. Please rate my reply. Thank you.

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When the timer has enabled the defrost cycle, the cooling mode ceases; the compressor shuts off and power is sent through the terminator to the heater. The heater warms and melts any ice build up on the freezer coil. The water drips to a pan and flows down the tube to a pan under the fridge - where it is evaporated off. The heater warms the freezer coil until either a) the timer returns to cooling mode or b) the terminator senses a preset rising temperature on the freezer coil. Once either condition is present, power is interupted and heating stops. The compressor is energized through the adjustable thermostat in your fridge. Since it is warm, the compressor turns on and cooling begins.

If any of the components listed above (1,2 or 3) have failed, the defrost cycle never warms the freezer coil and the ice never melts to clear the freezer coil as intended. Air can not be circulated through the freezer coil since it is choked with ice, so even though the compressor runs, the fridge and freezer spaces never get colder. The adjustable thermostat never sees the temperature you've set so the compressor never shuts off.

Water dripping in the fridge is melting ice from the freezer space - as the freezer is not getting colder - only the protected space around the freezer coil is.

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I hope this helps.

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