Frigidaire FPRH19D7LF1 refrigerator temperature fluctuations

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Old 01-15-17, 07:29 PM
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Question Frigidaire FPRH19D7LF1 refrigerator temperature fluctuations

TLDR: Fridge often gets too cold even after replacing thermistor and control board. What next?

I have a Frigidaire refrigerator, model FPRH19D7LF1, which is a refrigerator only (no freezer section). It has an digital control panel which displays the "set" temperature, but provides no indication of the actual temperature.

This refrigerator is in the garage and primarily used to cool drinks and bottles water, with occasional overflow items when there is no room in our inside unit. It is set at the default temperature of 38F.

After my wife complained of ice in her diet soda and then an exploded can, I purchased some refrigerator thermometers and placed them on an interior shelf and a door shelf. The two thermometers match each other when observed. Checking at various times, the temperature varied from as low as 22F to as high as 43F. This variation is somewhat random, but it is observed to be about 32F most often.

I replaced the thermistor, thinking it must be bad. This did not change these symptoms. Looking at the schematic, the only other part that I figured could be bad would be the control board. Today I installed a new control board. At first, I thought this had corrected the problem. For the first couple hours the temperature was right at 38F. I just checked it now, 8 hours after the repair, and it is 30F.

I am stumped. The shelves are not packed with items that could block air flow. The shelves along with door storage are about half full of beverage bottles or cans. The ambient air temperature in the garage ranges from 50F to 90F as I am in Florida. It is currently about 70F.

Any ideas would be greatly appreciated.
 
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Old 01-15-17, 08:44 PM
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Strange problem.

Since you changed the board and thermistor. Off the top of my head the first thing I can think of is a problem in the thermistor sensor wiring. There are several connectors in the path.

Pull the front kick plate off the fridge and look for the tech sheet. It will be the opening. You may need to lay down and look in for it. It has diagnostic routines on it for checking the controls.
 
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Old 01-16-17, 05:11 AM
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I thought about the wiring, but thermistor resistance increases as the temperature gets colder. Increased resistance through a connector would indicate to the controller that the temperature was colder than it is. This would not result in refrigerator temperatures lower than the set point.
 
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Old 03-07-17, 05:41 AM
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Frigidaire Temp Flucuation

I have the exact same model fridge and are experiencing the exact same issues. I just replaced the thermistor and experienced no change so I was curious if you ever got this resolved? Thanks in advance.
 
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Old 04-01-17, 04:45 AM
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May possibly be a design deficiency if the same issue is happening with the different sample of the same model. I have a Whirlpool that exhibits a large fluctuation in freezer temperatures, going from 0 deg F to 19 deg F with every cycle. I use an Accurite wireless thermometer to take readings, and it has a min-max feature to make it easy to record the range of temperatures and without opening the doors. The remote sensor was placed in an air tight container to get stable readings and slow its response for a better average on the measurement.

A whirlpool technician that came in to check it out said it is normal for this fluctuation to occur because they turn on the defrost on every cycle, which heats it up and allows it to get to 19 deg before resuming the cooling back down to the desired target of 0 deg. He suggested keeping the freezer empty instead of putting food in it to check if it gets better control, though that would be an impractical workaround even if it did work.

Had I known this was inherent in Whirlpool's design, I likely would have chosen a different refrigerator. Unfortunately, this is not a published specification, so it's not easy to determine which brands and models work with optimal temperature regulation.

The exact same test on a friend's refrigerator of a different make revealed temperature regulation within 2 degrees, which is significantly better than Whirlpool's 19 degrees of fluctuation.
I originally thought this was possibly from a zeal for energy reduction over performance, by reducing the on off cycles, since there's a surge in power required each time the compressor switches on, but turning on the defrost heaters seems counter to that goal.
 
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Old 06-23-17, 02:25 PM
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One note on this as I look back on it-

I found that the freezer setting should be set on max, because it essentially blocks the flow of cold air going down the the refrigerator and causes a much wider range of temperatures, because it lengthens the cycle times from the temperature sensor inside the refrigerator being isolated from the cold producing freezer section.
Once I set it on max, the temperature range was narrowed, and the food in the fridge was kept from spoiling for a much greater time than before, when it fluctuated up beyond 40 degrees in its regular cycle.
 
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Old 06-23-17, 02:55 PM
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A whirlpool technician that came in to check it out said it is normal for this fluctuation to occur because they turn on the defrost on every cycle
The defrost does not occur every cycle. The adaptive defrost control board is supposed to monitor running time and evaporator temps and then defrost based on preset parameters.
 
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Old 06-23-17, 03:14 PM
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Yes, I monitored it with the Kill-A-Watt meter and it doesn't come on with every cycle, as the Whirlpool technician incorrectly stated. I've got the settings on max for both refrigerator and freezer and it's working fine now.
I don't think they're that familiar with the details of the control designs, and are more used to handling outright failures. He suggested the issues were from having the freezer compartment full of food, which actually didn't have any bearing on it. The real fix in my case was putting the freezer setting to max to get a faster response time from the control loop.
 
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