Defrost Problems – The #1 Most Common Refrigerator Issue
Back in the old days a Refrigerators freezer would frost up fairly quickly, if you were opening them frequently to retrieve the food that they keep moisture within the air confined in the freezer.
Compartment quickly collects on cold surfaces and freezes forming frost the more moist air allowed to enter the freezer compartment the more frost would accumulate.
That’s one reason why keeping a good door seal is important. The same is true today. However, if everything is working properly you never see any of the frost because of the invention of the defrost cycle needing to manually Defrost your refrigerator every two months. Is not very convenient, so most modern refrigerators have this automatic defrost cycle.
There are Three Main Components in This Defrost System:
- A timer that keeps track of compressor runtime
- A small Bi-metal thermostat that senses if the evaporator needs defrosting
- And a heater that melts accumulated frost by generating thermal energy when it is supplied with 120 Volts.
Learn How to Fix Common Refrigerator and Freezer Problems
It’s not all gumdrops and rainbows though food cannot be preserved quite as long in an automatic. Defrosting refrigerators freezer as it can in a manually defrosting one due to the short rise and temperature from time to time to eliminate ice. One other issue is that you expect it to function properly in the days of manually defrosting. Refrigerators people would understand that they needed to let their appliance melt down every now and then to work properly.
But today if this unseen automatic system fails and frost appears or that cool glass of milk You just poured a suddenly room temperature people freak out because they don’t know what to do.
Air flow is crucially important for your refrigerator freezer to work properly. All cold Air is generated in the freezer compartment. And then it is circulated and forced into the refrigerator compartment by a freezer fan called the evaporator fan. Cold air from the Freezer is forced into the refrigerator and the slightly warmer. Air in the refrigerator is forced back into the freezer area to have the heat that it contains removed. If either of these air passages becomes blocked with frost or the automatic temperature controlling duct door called a diffuser sticks closed. The refrigerator will not receive any cold air from the freezer and even if the evaporator fan is blowing cold air directly into the refrigerator, if the air return is frozen closed.
It’s like blowing through a straw with your finger on the other side. The defrost timer is supplied power by the refrigerator’s main thermostat. Whenever the compressor is running in this way it calculates how frequently a defrost cycle may need to be performed. Most timers are set to initiate the defrost cycle after the compressor has run a collective eight to ten hours. Because the compressor is cycled on and off as needed by the refrigerators control thermostat – this could take 10 hours, if the compressor is running continually or a few days if the doors stay closed.
Most timers are mechanical however some models use a circuit board to perform the same task.
A defrost cycle starts when the defrost timer sends electricity to a small thermostat attached to a cooling coil called the evaporator. For more information about how a refrigerator works visit “How To Clean Refrigerator Colis”.
What is Bi-metal Thermostat
This thermostat is called a bi-metal thermostat. Because it has two small contact strips that flex with temperature change to open or close a circuit. In this case the bi-metal thermostat closes allowing electricity to flow through. When it is cold in this way the refrigerator will not energize the defrost heater, if there is no ice to melt. This thermostat is basically an automatic switch it is on. When it is cold if the thermostat is cold enough to be closed. Electricity passes through it allowing the heater to be energized. The heater temporarily becomes red-hot melting all the accumulated ice and tell the timer stop supplying power or the Bi-metal thermostat warms up enough to open breaking electrical flow.
The Most Common Cause of Defrost Problems
So now you know a little bit about how it works. Let’s see what can go wrong in order of Likelihood. The most common cause of defrost problems or ice buildup is user error. And let’s just say you have one too many cold ones and forget to close the refrigerator door in the morning. You sluggishly enter the kitchen for a cup of coffee and notice that the door is open. So you close it all that moist air accumulated in the refrigerator diffuser duct and became frost blocking cold air from entering the refrigerator.
Later that day you’re thinking about a nice cool beverage only to discover that the milk is warm and smells funny. You could call a repair service. But this scenario can usually be corrected by unplugging the appliance and allowing it to thaw out the old-fashioned way.
The most common mechanical failure
The most common mechanical failure is the Bi-metal thermostat failing to close and allowing power to flow through to energize the heater. The thermostat can be checked for continuity when it is cold if everything is frozen and the thermostat has infinite resistance. It needs to be replaced sometimes the defrost timer will fail to send electricity when it should. Mechanical timers can be manually advanced with a flathead screwdriver in the clockwise direction slowly. Until a click is heard at this point electricity should be sent through the hear to the thermostat some simple voltage tests can determine where the problem lies.
The circuit board style of defrost timer is a little more complicated to trick into a defrost cycle. So I’m not going to explain that but you can see how need do it on this video. Doing it wrong will definitely destroy the timer even if it was fine before and if you’re not careful. You can be electrocuted the last and least likely to fail is the heater itself. To test the heater unplug its contacts and do a resistance test. The defrost heater should have some resistance however an infinite resistance reading would mean that it needs to be replaced.
The entire defrost circuit can be tested when the freezer is cold by checking for. Continuity from before the thermostat through the defrost heater if the thermostat is closed. You should have a low resistance reading and you can assume that the defrost timer is not sending electricity.
We hope this article was helpful and saves you a bunch of money for more information on using test equipment and appliance repair troubleshooting. However you always can make an appointment visit appliance repairman by this phone (800) 657-0765