Bosch fridge temperature problem?

[Rollerball]

I have a Bosch fridge, the KIR21VS30G, this one:

https://www.bosch-home.co.uk/product-list/KIR21VS30G

It doesn't have a built in temp display or alarm so for some time I've had inside it a basic electronic thermometer (with no alarm).

I recently purchased a wireless alarm, the battery-powered wirelss sensor is placed inside the fridge, the main monitoring and alarm unit is of course outside it.

Usually I have the upper alarm temp set to 7C, however I recently lowered it to 6C.

During the past few days, and roughly at the same time of day, the temperature has briefly risen to just above 6C and set off the alarm. Out of 4 days this has happened twice.

The fridge is briefly opened by me at around 8:30 every morning (breakfast requirements ..... ) and the alarm is going off around 20 minutes later.

There are two possibilities for the alarm going off:

a) Maybe the temp has always briefly risen at the same time of day but I've never noticed it until I set the alarm on the external temp monitor, or:

b) the fridge is developing a problem.

Any other thoughts on possible causes?

 

[ETAF]

whats the temperature control set at, often you have 1-6 on the control
I recently had to change a thermostat in a fridge we have in the garage as it was NOT controlling the temp very well.
I like to have the fridge at around 4C

on the instructions from that link , should show you the temp and also theres is a setting (4) °C button Sets the temperature.
https://www.bosch-home.co.uk/produc...79/Togglebox=-2127238797/Togglebox=213040079/

Setting the temperature Recommended temperature
Refrigerator compartment:
Refrigerator compartment
+4 °C
■ Keep pressing the button °C until the display indicates the required temperature.

 

[Rollerball]

Sorry, I should have added that the fridge temp is usually around 3 to 4 C (I usually have it set it to 3 on the fridge settings) although today I lowered it to 2C to see if there's any change in the aforementioned morning timeslot in the next few days.

If the thermostat is at fault is it relatively cheap and easy to get a replacement? I feel that with my electronics knowledge I could swap it out myself if it's relatively easy to access.

 

[footprints]

Most thermostats certainly on heating appliances do not click in and out at the same temperature to prevent constant cycling, there is usually a few deg lag between them. may well explain the temperature not remaining absolutely constant. Racking my brains for the correct technical name for the delayed operation of thermostats but the grey matter is not working today!

 

[Rollerball]

Thanks, that does actually makes sense. Maybe I just need to adjust my wireless fridge alarm sensor not to trigger so soon.

 

[ETAF]

hysteresis

Could be easy to swap out , mine was and also had to get the right part , quite a few look the same, ONLY issue will be how its all connected into the electronics
Mine was a simple unit all complete and so changing was just 3 spade connectors

I have a 4 sensor BBQ unit IBT4XS - so i used that inside the fridge and monitored the temp over time, it gives me a graph -
The original one was setting 5 about 12C and then turn to setting 6 and it went to freezing -1 ish , scale was 0-6

Changing I got a reasonable temp between 2 and 6 , so was happy with that

I used spares at UK Whitegoods
But also saw it on espares, a lot more pricey
i confirmed the part with them via email [email protected]
As just the suffix letter on the part number made a lot of difference to the unit function and connection

All sorted during lockdown 1

 

[Rollerball]

Thanks very much, very useful. Let's hope I don't need to swap mine out.

BTW, about that thermometer you use, what temp does it measure down to?

 

[footprints]

ETAF Thanks that is it. So I will not wake up at 3am still puzzling about it!

 

[Rollerball]

Just to get back to this, I checked the fridge temp before opening it at around 7:30 this morning and it was at 6.1, however it soon dropped backed to 3.3

It can't have been at 6.1 for long either because my wireless alarm only goes off when the max temp (set to 6C in this case) has been exceeded for ten minutes.

Is this simply the fridge thermostat's hysteresis not being particularly sensitive?

As the thermostat setting is set to 3C should it normally take around a 3 degree increase in temp before the thermostat kicks in and starts to cool again?

And why is this only noticeable first thing in the morning? Yesterday I was checking it every hour or so during the day and it was always around 3C, I even saw it at 2.1 briefly. Is it an overnight thing because the fridge has been closed for maybe 10 hours and because there have been no temperature variations due to opening the door the thermostat hasn't needed to kick in?

I'm wondering if it's been like this since I got it and I'm now only noticing it because I'm monitoring it closely.

I'd phone Bosch and ask about this but as evidenced by my other thread (https://www.diynot.com/diy/threads/...rovide-a-quality-tech-support-service.569364/) they are useless (only reading from the user's manual) and don't even offer any telephone advice or any level of in-depth tech support on the phone.

 

[Lower]

The fridge is probably going through a defrost cycle to allow any ice that's formed to melt and drain away.

 

[Rollerball]

That's a very good point, I hadn't thought of that.

Is a defrost cycle usually activated after a specific number of hours or is it determined by other factors such as the thermostat setting?

Although I guess it depends on the make and model of fridge.

 

[Lower]

That's a very good point, I hadn't thought of that.

Is a defrost cycle usually activated after a specific number of hours or is it determined by other factors such as the thermostat setting?

Although I guess it depends on the make and model of fridge.

I would imagine it will relate to the thermostat setting. The lower the set temperature the more ice formation and therefore more defrost cycles.

I doubt your fridge has a problem.

 

[Rollerball]

Thanks.