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-   -   Magic Chef Refrigerator not cooling (http://www.houserepairtalk.com/f11/magic-chef-refrigerator-not-cooling-7148/)

grmorse 07-21-2009 03:20 PM

Magic Chef Refrigerator not cooling
 
My Magic Chef side by side refrigerator (model number GS22Y8D) appears to have stopped cooling. I just noticed that milk is warm and ice cream is soft. I have heard no unusal noises. I am not sure if this is related but the ice maker has not been working for some time and i just filled the bin with store bought ice.

Nestor_Kelebay 07-21-2009 11:13 PM

If your fridge has digital displays showing the actual fridge temperature and target temperature and stuff like that, then it's possible that the circuit board that controls the fridge is shot.

However, if your fridge doesn't have digital electronic controls like this, and this is a problem that's just come on with no warning, then I'd suspect your defrost timer is stuck in the defrost mode. Read on...

Every frost free fridge, whether it's a freezer-on-top model or a side-by-side will have something called a "defrost timer", which is the "brains" of the fridge.

It's very possible that your fridge's defrost thermostat is stuck in "defrost mode". In that case, your fridge won't cool at all. It'll just keep trying to defrost itself until the defrost timer advances and puts the fridge back into normal operation.

The defrost timer diverts power from the thermostat (or "cold control") for about 20 minutes every 12 hours or so, and sends that electrical power to the defrost heater instead. The defrost heater melts any frost off the evaporator coils of the fridge, and that melt water drains down a tube to a receiving pan typically located on or around the warm compressor of the fridge where that water evaporates into the air in your kitchen. Typically, the fridge's thermostat (or "cold control") will energizes both the fridge's compressor and the evaporator fan at the same time to start the fridge cooling. So, typically both the compressor and evaporator fan will start and stop at the same time. Thus, when the defrost timer diverts power away from the thermostat at the beginning of a defrost cycle, both the compressor and evaporator fan (the fan that causes he slight breeze in the freezer compartment) will go off simultaneously. And, will both come on simultaneously at the end of the defrost cycle when power is restored to the thermostat if the thermostat is calling for cold at the end of the defrost cycle.

DURING the defrost cycle, the power will be diverted to the defrost heater who's job it is to melt any accumulated frost off the evaporator coils (which is where the refrigerant evaporates, thereby absorbing heat from it's surroundings). If the styrofoam parts in that area of the fridge get too warm, they'll melt, and so a defrost thermostat wired in series with the defrost heater will shut off the current to the defrost heater if things get too warm in the vicinity of the evaporator coil during the defrost cycle. If the defrost thermostat shuts off the defrost heater, then the fridge will just sit there as if in a coma until either that area cools down again and the defrost thermostat allows power to flow to the defrost heater again, or the defrost timer completes the defrost cycle and diverts power back to the fridge's thermostat (which controls the fridge's compressor and evaporator fan).

But, defrost timers in fridges typically have tiny motors that can get stuck from a bit of friction, and that can cause a problem from no cooling at all to no defrosting at all so that frost starts to form inside the freezer compartment. If the defrost timer sticks in the defrost mode, then there's no cooling. If it sticks in the normal operating mode, then there's no defrosting. And, an intermittently sticking defrost timer can give you everything in between. My personal view is that it's a good idea to replace the defrost timer on a frost free fridge every 10 years just as preventive maintenance.

Defrost timers will have an output shaft that turns the cams in the defrost timer that make and break the electrical connections, and you should be able to easily access that output shaft. The output shaft will be designed in such a way that you can only turn it in one direction with a slot screw driver. That's because you can wreck a defrost timer by turning it backward.

I'd contact my local Magic Chef factory authorized repair depot and ask them where to find the defrost timer on your model of fridge. Once you find the defrost timer, located the shaft on it, and turn it until you hear the defrost timer "click". If the fridge fires up and starts cooling again, then you had a stuck defrost timer, and you need to replace the defrost timer with a new one.

If turning the output shaft of the defrost timer doesn't cause the fridge to come to life, then I'd suspect that the fridge isn't stuck in defrost mode, but that the fridge's thermostat is the problem (it's not calling for cold). If, when the defrost thermostat "clicks", the evaporator fan comes on, but not the compressor motor, then I'd expect the start relay on the compressor is the problem. You can diagnose problems like this because typically the fridge compressor and the fan that causes the slight breeze in the freezer section of the fridge will always go on and go off simultaneously. So, if one comes on but not the other, then you can assume the problem is with the evaporator fan or compressor if it doesn't start working when the other one does.

grmorse 07-27-2009 09:09 AM

defrost heater
 
thank you so much for the detailed reply. I have now taken off the back which revealed much frost buildup. I tested the defrost heaters and got no reading on the ohm meter. I did not test the defrost timer since I figured it is the heater that is the problem. However, the defrost time is only 10$ part so I think I will just replace it per your suggestion as preventative maintenance. thanks.

Nestor_Kelebay 07-27-2009 11:19 AM

If you didn't get continuity across the defrost heater, then your defrost heater is gone and that's the reason why your fridge isn't defrosting. That in itself can cause a cooling problem because if the frost builds up to cover the vents where the cold air enters the freezer compartment, then your fridge appears to have stopped cooling.


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