# What can cause huge freezer temperature swings?



## seabeast (Jul 30, 2013)

We have a fairly new Whirlpool side-by-side refrigerator freezer in the garage that doesn't keep freezer foods properly frozen. We had an appliance repairman come out, but the freezer was quite cold when he checked, and he couldn't find anything else wrong. The condenser coils were clean, the frost pattern looked good (??), the fan was blowing air, nothing was obstructed or overloaded, etc. He left without fixing anything.

So I bought a couple temperature monitors from Amazon (the very cool SensorPush units) and put them in the freezer and fridge compartments to see what was going on. I discovered the freezer temperature cycles over a roughly 40 degree F range (-10F to 29F) every four hours. It stays below freezing, but just barely. And with these settings, the refrigerator compartment cycles below freezing at the same period.

To get a point of comparison, I moved the sensors to our kitchen fridge (a SubZero), and then plotted everything in the image below. As can be seen, it does a _much _better job of maintaining the freezer temperature, keeping it in a narrow band around -4F.

I've done some searching, but I cannot find any clear spec or guidance for how much temperature variation is normal or acceptable. Is there a spec or guideline for this? Any thoughts on what could cause such large temperature swings? Any particular components that ought to be checked to diagnose this?


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## Chris616 (Dec 31, 2019)

What is the model number for the Whirlpool?


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## seabeast (Jul 30, 2013)

Sorry, should have included that: Model WRS315SNHM06


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## bfrabel (Oct 22, 2017)

Does the garage where this thing is at stay at a nice even temperature that's similar to the temperature that your house is kept at?

If not, that's your problem. These things aren't designed to operate in unconditioned spaces. 

The thermostat in these things is in the refrigerator section. The compressor turns on and off based on that. It turns on when the refrigerator section gets to about 40°, and off when it gets to about 32°. The freezer section just gets what it gets. Under normal operating conditions, this works out to keep stuff inside of the freezer somewhere around an average temperature of about zero°F.

If your freezer needs to be in the garage, you might need to get a seperate, dedicated freezer.

If your refrigerator needs to be out there, and the temperature in the garage drops below freezing, you will risk the things inside freezing, since they aren't designed to keep things inside warmer than outside.

Either way, you also risk an early death to the compressor, since operating in cold ambient conditions is hard on them.


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## Half-fast eddie (Sep 19, 2020)

Is the frost-free cycle kicking on?


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## seabeast (Jul 30, 2013)

The refrigerator is by an inside wall in an attached garage in sunny San Jose, California, so it shouldn't see temperatures much different than inside a house, and certainly nothing near freezing. As you can see on my graph, the cooling is starting when the fridge is around 36 and running until the fridge compartment is around 27, which is much colder than ambient temperatures and also too cold for a fridge. The temperature control panel only has four "coldness" settings, and I have it in the recommended middle setting (_not_ set to max cold), so it really shouldn't be freezing the fridge compartment. Our daytime temperatures are in the 60s and 70s, and I saw that four-hour cycle of giant temp swings throughout the entire day I monitored it.

But investigating this is a good idea: I'll put a temp sensor in the garage by the fridge, and the other inside it (sounds like the fridge compartment is more meaningful than the freezer compartment), and see what that looks like over a multi-day period.

Thanks for the debug help!


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## seabeast (Jul 30, 2013)

Half-fast eddie said:


> Is the frost-free cycle kicking on?


No idea. But since the temperature slowly drifts up over several hours and then cools rapidly, could that even be explained by frost-free kicking in?


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## Chris616 (Dec 31, 2019)

Whirlpool doesn't make it easy to find the operating manual for this unit. Does the control panel for the fridge look like the graphic below?


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## seabeast (Jul 30, 2013)

Chris616 said:


> Whirlpool doesn't make it easy to find the operating manual for this unit. Does the control panel for the fridge look like the graphic below?
> View attachment 682861


Yes, that's it. The only thing I adjusted away from the default recommended settings is to move the freezer temp slider all the way towards cold, to minimize airflow between the freezer and fridge.


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## huesmann (Aug 18, 2011)

There may be an air duct that goes between the freezer and refrigerator sections that is on the fritz.


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## Chris616 (Dec 31, 2019)

(I spent a long time looking at your graph and trying to understand what was happening, so it seems that I’ve written a novel putting it all down in writing)

Thanks for providing useful data with your post. We get so many where people complain of something being too hot or cold or pressure being too high or low, etc. but most of them can’t give actual numbers.

Your Sub-Zero has separate compressors for the fridge and freezer, so it is simple for it to maintain the setpoint temperature in each.

It’s the average temperature in the freezer that is the important thing, as long as the high point never gets above freezing. I made an estimate of the average temperature that the food is seeing by drawing approximately equally sized purple and yellow areas under one of the curves. If those two areas are equal then the average temperature would be about 5F, which isn’t bad.

I did quite a bit of searching, like you’ve done, and I also could not find any reference material on what is a “normal” temperature range between what is called the “cut in” and “cut out” temperatures of the thermostats. A 40F degree range seems unreasonably large, though.

When I look at the parts available for your fridge, there are no thermostats, so it seems that the temperature control for the fridge and freezer is done by a printed circuit board (PCB). It gets the temperature reading from the fridge and freezer via a thermistor located in each compartment. Thermistors are simple devices for which the electrical resistance across them changes with temperature. The PCB just reads the resistance and converts that to the known temperature for that thermistor. So, there don’t appear to be any possibly faulty thermostats to replace. Just the thermistors, which are inexpensive but reliable, and the PCB which is the opposite.

There is something in the excellent graph that you uploaded that I find odd. My understanding (which may be faulty) of how typical single compressor fridge/freezers work is as follows. The thermostat for the freezer controls operation of the compressor. The thermostat for the fridge operates dampers or fans that allow air exchange between the fridge and freezer. So when the fridge gets too warm it brings some cold air in from the freezer. In a graph like the one that you uploaded for a unit like that you’d expect the peaks and valleys of the fridge and freezer temperature to occur at different times. But that isn’t what is shown in your graph, where the peaks and valleys coincide. I think what is going on here is that in their never ending quest to make a cheaper unit, Whirlpool has eliminated the automated control and instead put in a crude human adjustable opening between the fridge and freezer. In this scenario when the fridge gets too warm the compressor starts and some of that “coolness” flows into the fridge from the freezer until the “cut out” temperature of the fridge is reached and the compressor is turned off. So if the load on the fridge side is low (maybe because the garage temperature is low) the compressor doesn’t have to run so often to keep the fridge at the right temperature. And if the compressor doesn’t run so often the freezer compartment ends up warmer than it might if the load on the fridge was higher. 

That previous paragraph might be complete hogwash, but if you do some more temperature logging when the garage temperature is higher I’d be interested in seeing the output.


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## seabeast (Jul 30, 2013)

Glad you liked the graph! I'm pretty pleased with it myself...

Full disclosure: I only have two temperature logging devices, so the data in the plot is aggregated over a few time periods. However, I doubled-checked the Whirlpool fridge vs freezer temperatures, and those _were _collected simultaneously, and the graph lines them up correctly: so they really do increase and decrease in perfect unison.

I haven't downloaded and plotted the new data yet, but I put one sensor in the Whirlpool fridge compartment and the other on a shelf outside the refrigerator, and collected data for 24 hours. The garage temperatures ranged from a high of 68.2F to a low of 59.1F. Whirlpool states the fridge "should" be placed in an environment that stays between 55F and 110F for efficient operation, so I believe my garage counts as a perfectly acceptable indoor location for their purposes. During these 24 hours, the fridge followed the same pattern as the earlier graph, cycling between 28F and 37F over a roughly 4-hour period (the cycles got a little slower as the garage got colder).

My understanding of how a simple single-compressor fridge would work matches yours, though I think the average temperature must be measured over some reasonably short time, like maybe 30 minutes, and not arbitrarily long. A four hour cycle seems really long to me, at least if the temperature variation is so far from the average.

I agree the vent between compartments seems like a possible culprit. If the fridge works by turning on the compressor whenever _either _compartment gets too warm, but the vent between them was stuck too far open (or the fan was always on), then the fridge section would stay too cold and the compressor would only turn on when the freezer got close to thawing. As mentioned, though, I currently have that vent set all the way to "freezer colder", which _ought _to be closing it. Guess I could try moving it back and see what happens. Pretty sure it was in the middle when we previously found our ice cream melted.


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## seabeast (Jul 30, 2013)

Some new data! The plot below shows results of some experiments over the past several days. After a day of just monitoring things with default settings, I tried using painter's tape to cover 2/3 or so of the vent between the freezer and fridge sections. This dramatically changed the behavior, for the better.

Then I tried adding a six pack of warm drinks, which caused the fridge temp to spike, so I panicked and peeled back a bit of tape and set the controls to Hi (4 snowflakes, up from default of 3). That seemed to stabilize at a pretty good place, but the temp swings were larger than I liked, so I put a little of the tape back. That's where it is now. Not a solution, but an interesting hack that at least works fairly well for now.










In other progress, I found a service manual that had instructions for enabling self-test mode. Alas, all tests passed so nothing very interesting was learned.

I scheduled another Whirlpool service, and this time I'm ready with data. Hopefully this plot will not only convince the tech there's a problem, but lead to a diagnosis of what's wrong.


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## Chris616 (Dec 31, 2019)

That section when you increased the load by adding warm drinks to the fridge did force the compressor to work more and so reduced the temperature swings of the freezer. I suspect that the technician isn't going to find anything not working as designed. It's just that the design is poor.


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## Zulu Kono (Nov 2, 2021)

Had a Whirlpool that did the exact same thing.
I have an LG now.


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## RAL238 (May 20, 2018)

My guess is that you have a bad controller board. Or perhaps a bad thermister in the freezer compartment.


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## Rickbe (11 mo ago)

seabeast said:


> Some new data! The plot below shows results of some experiments over the past several days. After a day of just monitoring things with default settings, I tried using painter's tape to cover 2/3 or so of the vent between the freezer and fridge sections. This dramatically changed the behavior, for the better.
> 
> Then I tried adding a six pack of warm drinks, which caused the fridge temp to spike, so I panicked and peeled back a bit of tape and set the controls to Hi (4 snowflakes, up from default of 3). That seemed to stabilize at a pretty good place, but the temp swings were larger than I liked, so I put a little of the tape back. That's where it is now. Not a solution, but an interesting hack that at least works fairly well for now.
> 
> ...


I have a similar model Whirlpool fridge with the same problem. I had a service tech come out and he just said my garage was too cold without even checking the fridge. I put a heater in my garage and still had the same issue with big swings in freezer temp and refrigerator section too cold (garage temp was about 72F). I covered about 3/4 of the vent with painters tape based on your post and that has resolved the issue.


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## seabeast (Jul 30, 2013)

Glad my experimentation has helped someone else!

My next visit from Whirlpool service is scheduled for Tuesday. When I called the Whirlpool support phone number, I asked if it was possible for me to speak with someone technical, and Whirlpool told me they don't have a technical support line for consumers, but there is a number their service people can call, and they'd annotate my service request with a note that the tech needed to call in to speak with them when he's on-site. And when the service company called to schedule the visit, they said they had to schedule when the Whirlpool tech staff was available, so I'm hopeful I'll get a more definitive diagnosis this time.

I really find it hard to believe that a system is working as intended if something as simple as a strip of painters tape makes it work much better. Fingers crossed they agree.


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## seabeast (Jul 30, 2013)

An update to this saga: the Whirlpool service technician arrived today and was suitably impressed by my graph of temperatures. Summary of our discussion:

This is a common-enough issue that Whirlpool has issued a service bulletin to deal with it.
Step #1 is to replace the electronics assembly, which I believe he described as including the control board, thermistor, and baffle. He placed the order for these parts; no idea yet how long it will take for them to arrive and get installed.
If that doesn't work, step #2 is (wait for it...) to use tape to block roughly 1/2 of the air return vent. Unlike my crude exposed painter's tape on the top vent, the pros apparently use foil tape to block the air return at the bottom of the fridge, behind the grill so it's not visible. Fancy!
If that doesn't work, complain to Whirlpool and have them replace the fridge or something.
Also, best not to mention the whole "it's in the garage" thing to Whirlpool, since they like to claim that's The Problem and deny further help, but the technician agreed that the garage location is not a problem in my case (well-insulated garage, inside wall, California, etc).
He really liked my temp sensors. He said Whirlpool used to (??) provide little logging devices they could leave in customer's fridges for a few days, which they'd then mail in to Whirlpool for analysis. Sounds like they don't do that anymore, or at least not regularly.
I'm not sure if step #3, the tape over the vent, is officially sanctioned by Whirlpool, or just something a fellow technician suggested. But he said tape has worked for him in the past, so I'm on the right track and should leave my tape in place at least until the replacement parts arrive.


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## seabeast (Jul 30, 2013)

The fridge guy came,
The fridge guy went,
And now it's time for me to vent.

The technician replaced the control board, the thermistor, and the baffle connecting the freezer with the fridge.
Result: no meaningful change in behavior.

And worse, so far I haven't replicated the magic amount of vent-blocking tape to get the performance to match what it was before the technician "fixed" it. Sigh.
I'm not sure yet what my next move will be. The technician had nothing good to say about the control system used in this Whirlpool fridge. Apparently the same controller was a frequent source of complaints in a prior model, so he was disappointed they're still using it.

Looks like I won't be buying Whirlpool fridges in the future.


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## gthomas785 (Mar 22, 2021)

A couple of questions that haven't been covered yet.
-Does your freezer have a light
-How full is the freezer

I notice that your freezer temp is rising more than 15 degrees F in the first hour after the compressor kicks off. That's concerning to me and suggests it could be the light stuck on, or the defrost heater is stuck on, or there's air leaking into the freezer compartment from outside.


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## seabeast (Jul 30, 2013)

gthomas785 said:


> A couple of questions that haven't been covered yet.
> -Does your freezer have a light
> -How full is the freezer
> 
> I notice that your freezer temp is rising more than 15 degrees F in the first hour after the compressor kicks off. That's concerning to me and suggests it could be the light stuck on, or the defrost heater is stuck on, or there's air leaking into the freezer compartment from outside.


I don't think I mentioned it previously, but another experiment I did was the unplug the refrigerator for a couple hours and watch the temperatures, to see if maybe the defrost heater was stuck or something. The temperatures in both compartments rose at the same rate as normal, so I concluded nothing is actively heating either side.

The door seals appear perfect, and two different service technicians specifically checked them, so I don't think there's a leak. But that one is harder to prove definitively.

-Brett


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