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I have a fridge that seems to have an issue with wildly fluctuating temperatures. I noticed that some food seemed to have been thawed and refrozen. (This is an extra fridge in the basement, so I'm not regularly in and out of it.) The fridge section seems to be okay. The only problem there are temps that are sometimes TOO cold, but I think that's only because I set the controls too low to try to keep the freezer cold.
One day I noticed that there was a heating element glowing red through the opening in the back of the freezer unit. I assume that's the defrost heater. The freezer was definitely too warm at that point. I've been trying to track the temperature swings. Just today I noticed it go from below 0 to 60 degrees in less than 2 hours. Shortly after it was back down to 30 and dropping.
I read about some similar situations, but there seem to be a variety of underlying causes -- defrost timers, defrost thermostats, bad circuit boards, etc. I'd love it if someone could give me some methodical steps to follow in trying to troubleshoot this. I don't mind putting a meter on various parts, but I need some help in knowing what things to test on which parts. I really don't want to just blindly replace parts until I hit the faulty one. I'd appreciate any help.
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Rank: Member
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I took the back panel off the freezer. There are actually two thermostats connected in series. I think they're identical. I'm pretty sure I can disconnect the wire at one end, but the feed from the back is continuous to the thermostats. Is there any way to test them without cutting wires??
Also, I noticed that the defroster has been on several times today. Is that normal?? I read somewhere that it should run only once every day or two. (If it's based on compressor run time, maybe the problem feeds on itself -- the more defroster time, the more compressor time, the more defroster time?)
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You should only have one defrost thermostat. Symptoms point to a shorted thermostat and a bad defrost timer. I would replace both and use a single thermostat.
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Rank: Member
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Thanks for the response, Rich. Appropriate that it's from State College, since I'm a Nittany Lion.
I was surprised to see two thermostats in there, but that's how the diagram shows it as well. Interesting thought to replace them with just one. They're shown as the same part number, so I can't imagine they have different functions. Seems like it just increases the possibility of failure.
By the way, I pulled out the defrost control module. I confirmed that it's showing continuity to the compressor line. However, it's a completely electronic board, so I can't manually move the timer into defrost mode in order to test the defrost continuity. Is there any way to test that? Or is there no real point to testing it because I know that it cycles into defrost mode?
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Rank: Advanced Member
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Normal defrost intervals are 9 hours between defrost, seems like you have a bad control module.
If your schematic shows a wire from the module to the defrost circuit, you could pull the power connector off the control module, then insert a wire jumper between that mating pin and the one labeled line. Should initiated defrost.
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Rank: Member
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In an attempt to show some basic level of responsibility, I'd like to provide a followup. I ordered two replacement thermostats. Given the cost of shipping, I figured I'd get both of them, but I didn't want to spring for the cost of the module. However, I followed Rich's suggestion of using only one thermostat. It was easy and quick. To test the repair, I put a container of ice cubes in the freezer. After 60 hours of running, the ice cubes were still frozen and separated, indicating that the temperature had not been near 32F for any length of time.
I have not yet tested the old thermostats. If I do, I'll post the results on whether both are bad. My guess is that they put two thermostats in there because they expect them to fail sooner rather than later, so they're buying some additional time. I suppose I appreciate the attempt to buy some extra time, though it's really a kludge. Meanwhile, I'll tape the extra thermostat to the back of the refrigerator and hope that I'll never need it.
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Rank: Advanced Member
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This all makes no sense, thermostats blow open, using two of them reduces the reliability by 50%
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