Is my freezer temperature too unstable

@jayeff looking at the regularity of time and temp, I wonder if this could be an issue with some Auto defrost setting/part?

@oldturkey03

I wondered about this also but looking at the parts list it seems that they either used the freezer temp sensor (aka evaporator sensor) for both functions i.e. freezer temperature control and auto defrost "control" i.e. signals when to turn off the defrost heater and end the defrost cycle or it's a fully timed event by the control board i.e. set timed period, when to start and when to stop auto defrost.

Could be that the board measures accumulated compressor run time (it controls when the compressor is turned on and off) so it could work out for how long it ran each time before the auto defrost had to happen.

Usually the defrost cycle start time could vary from every 8 hours to over 24 hours depending on ambient temps and user activity. Older refrigerators did this with the defrost timer but this model hasn't got one so it must be controlled by the board.

If the auto defrost cycle was based on a set compressor run time period then it should happen once every 8-10 hours as most of this type are and not every 90 minutes

I assumed that the service techs would have run the diagnostics (I can't find them online) to make sure that all the functions were as they should be, so presumably the sensors and the control board all tested OK

Cheers

Thank you for the feedback. On both of the new Whirlpool units, the refrigerator temp was fine - it stayed consistently in the mid 30s - not a lot of fluctuation. On the first new freezer, the tech started noted "the system was restricted at the filter drier. Installed new dye drier, flushed the system with nitrogen, pulled a vaccum and charged to factory specs." This did not change anything. On the next visit the tech noted "Pressures took a long time to equalize which indicates the system is still restricted. No signs of leaks anywhere. We need to cut out the evaporator, blow through the cap tube, and install a new evaporator." Next visit they noted "cut out the evaporator, flushed with nitrogen, and installed a new evaporator. All pressures good after charging and we are getting a full frost pattern." This also did not change anything (freezer temp still never got to 0 and fluctuated just like in the graph above). Comments continued below. . .

On the next service call, the tech noted "Low side running in a vacuum and pressure equalized at 6 psi. Charged with nitrogen to check for leaks and looked for dye. No signs of leaks externally." At this point they concluded it was un-repairable and replaced it with the second new unit on which I measured the graph above. I tried the paper test and the door seals seem to be good all around.

@scottkoefod

Looking at the product sheet for the model series, it shows that it has 'adaptive defrost" which means that the defrost occurs when needed, based on compressor run time and number of door openings. Presumably both are related to how often the compressor has to run for (and for how long) as well as the number of times the doors are opened over a known time frame.

The temperatures you measured do behave as though the defrost cycle is occurring, but I don't think that it should happen that often, especially if it also happens overnight as presumably there's not much door activity happening.

All I can think of is that it might be a control board problem perhaps (firmware??) or a faulty door switch (can you prove that the light in the freezer compartment does turn off when the doors are shut by manually operating the door switch when the door is open?) as these are th etwo components that can affect the defrost cycle.

The other interesting thing is that the parts list doesn't mention a tech sheet, which is highly unusual in a Whirlpool parts list as nearly all do, Whirlpool doesn't provide them either so unfortunately without it I don't know how to run the diagnostics to check what may be wrong.