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Freezer cold / fridge warm PDF Print E-mail

QUESTION

My freezer seems to be cold but my fridge part is too warm. The back wall of my freezer seems to have a little bit of frost on it. Is this a big problem?

ANSWER

Your refrigerator is a large heat transfer device. It simply takes heat from one place ( inside the fridge) and puts it somewhere else, usually in the surrounding area. Anything that interferes with this process can cause cooling problems.

Freezer cold/fridge (fresh food part) warm is not an uncommon problem in a fridge that has a separate freezer compartment.

There are a few possible reasons for this to occur but the two most likely are:

1) The fresh food (fridge) part of your refrigerator gets its cold air from the freezer . (There are exceptions to this rule in some generally more expensive units) . The ‘cold’ part of the freezer is called an evaporator. It is usually behind the back wall or in some cases under the floor of the freezer compartment.  If something is interfering with the air flow, you can have a not cold enough fridge but the freezer seems OK.

Most modern refrigerators use a fan to move air in the freezer through the evaporator and push it into the fridge compartment. Sensor(s) tells the control when the required temperature is reached and turns the compressor off. The sensor may be located in the fresh food (fridge) part because if the fridge part is at the right temperature, usually the freezer is cold enough.

If your evaporator fan, (located in the freezer),  isn’t running, the air can’t be moved through the evaporator but it will still run the compressor because the fridge sensor wants it to be colder. This means that your freezer will be cold but the fresh food (fridge) part won’t.

If your compressor is running and the evaporator fan in your freezer isn’t, that could be the problem. In some cases, a very noisy evaporator fan can be the culprit. It may be running intermittently as a result of overheated bearing, etc. Note that there are makes of refrigerators where the evaporator fan turns off when you open the freezer door. You may have to push the door switch in to make the fan run. If there is no visible door switch on the freezer door, you may have a magnetic reed switch, suggest you call your local appliance service company for advice on how to activate the switch with the door open.

2) From the above answer, there is another possibility. When the air passes through the evaporator in your freezer, it is cooled down and loses moisture resulting in cold dry air. The lost moisture freezes onto the evaporator itself resulting in a layer of frost forming. This frost actually slows down the heat transfer between the air and the evaporator. Too much frost (ice) can block the air flow and substantially slow down any heat transfer. No air movement, slow heat transfer - your freezer can be cold but not the fresh food (fridge) part.

To get around this, manufacturers have created a defrost cycle found in ‘frost free’ refrigerators. Every so often a timer turns off the compressor and turns on a heater in the evaporator. This literally melts the frost / ice off the evaporator and allows for heat transfer again. This is a timed cycle, usually about 20 minutes. There is a safety feature built in called a defrost termination switch (thermostat) that makes sure it doesn’t get too hot in the freezer. If any of the parts of the defrost system fail, your freezer can ‘ice up’ and your freezer can seem cold but your fresh food section is too warm.

A simple test for a defrost issue is to unplug your refrigerator and leave the freezer door open for at least 10 hours or until the rear wall / floor of the freezer seems no longer cold to touch. Yes, there are ways to speed this up but safety and damage are serious issues. Then plug the refrigerator back in. If it seems to be working normally about 30 minutes after plugging it in, it is probably a defrost problem. It will still require repairs but should behave itself for about a week, (Southern Alberta has a usually low humidity so freezing up takes a little longer). 

There are many ways used to control modern refrigerator operations and generally it is best to have an appliance service technician check your refrigerator. Some use computer boards to control defrost cycles and multiple sensors for temperature. In some the compressor never fully turns off, (variable speed). This is actually more energy efficient.

 
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