We have an AEG fridge/freezer combination with Santo 'fuzzy logic'
temperature control. It has controls on the front for adjusting the
fridge and freezer temperatures, with a digital readout giving the set
and actual temperatures. I had reason to measure the fridge
temperature recently, and found it much higher than indicated on the
digital readout (I used both a mercury-in-glass thermometer, and a
K-type thermocouple with electronic meter, and left them overnight to
stabilise). With the set/actual control reading 3°C, in reality it was
only getting to 7°C, too high for my liking. Turning the control to
minimum (2°C), only brought the temperature down to 6°C, still a bit
high (I would like 4°C). The problem seems to be with the electronics
interpreting the signal from the temperature sensor, i.e. it sees 6°C
as 2°C. 

The freezer section suffers in the opposite direction: it's set to
-18°C but actually stabilises at -23°C. I'm not too concerned about
this, because I can simply adjust the set point to a higher value, say
-15°C if I want it less cold, but I can't persuade the fridge to get
any cooler.

Can I adjust something so that the internal and indicated temperatures
are the same, or at least closer together? Where are the control
electronics located, and how do I get into them? Can anyone advise?

(The fridge/freezer is located in a utility room, away from heat
sources, and with plenty of air circulation around the back. The two
compressors are not running flat out, but cut in and out as normal).

-- 
 
Chris

E-mail: christopher[dot]hogg[at]virgin[dot]net

>I had reason to measure the fridge
> temperature recently, and found it much higher than indicated on the
> digital readout (I used both a mercury-in-glass thermometer, and a
> K-type thermocouple with electronic meter, and left them overnight to
> stabilise). With the set/actual control reading 3°C, in reality it was
> only getting to 7°C, too high for my liking. Turning the control to
> minimum (2°C), only brought the temperature down to 6°C, still a bit
> high (I would like 4°C). The problem seems to be with the electronics
> interpreting the signal from the temperature sensor, i.e. it sees 6°C
> as 2°C. 
>

Just a thought, but fridges are tall boxes, and if left to stabilise I
would expect quite a large temperature gradient, ie the top (where you
keep the butter etc) being a fair bit warmer than the bottom.

Where did you put your sensor?
Try near the bottom and see what you get.

I would also think that there is a fair bit of hysteresis (can't spell)
so put the sensor in a lump of something (tomato?) to average out the
variation and see what you get.

On Aug 15, 6:05 pm, Chris Hogg  wrote:
> We have an AEG fridge/freezer combination with Santo 'fuzzy logic'
> temperature control. It has controls on the front for adjusting the
> fridge and freezer temperatures, with a digital readout giving the set
> and actual temperatures. I had reason to measure the fridge
> temperature recently, and found it much higher than indicated on the
> digital readout (I used both a mercury-in-glass thermometer, and a
> K-type thermocouple with electronic meter, and left them overnight to
> stabilise). With the set/actual control reading 3°C, in reality it was
> only getting to 7°C, too high for my liking. Turning the control to
> minimum (2°C), only brought the temperature down to 6°C, still a bit
> high (I would like 4°C). The problem seems to be with the electronics
> interpreting the signal from the temperature sensor, i.e. it sees 6°C
> as 2°C.
>
> The freezer section suffers in the opposite direction: it's set to
> -18°C but actually stabilises at -23°C. I'm not too concerned about
> this, because I can simply adjust the set point to a higher value, say
> -15°C if I want it less cold, but I can't persuade the fridge to get
> any cooler.
>
> Can I adjust something so that the internal and indicated temperatures
> are the same, or at least closer together? Where are the control
> electronics located, and how do I get into them? Can anyone advise?
>
> (The fridge/freezer is located in a utility room, away from heat
> sources, and with plenty of air circulation around the back. The two
> compressors are not running flat out, but cut in and out as normal).

Could probably be fixed with a resistor, but you'd need to show us the
circuit diagram.


NT

On Fri, 15 Aug 2008 15:57:10 -0700 (PDT), meow2222@care2.com wrote:


>Could probably be fixed with a resistor, but you'd need to show us the
>circuit diagram.
>
>
>NT
I wish....

-- 
 
Chris

E-mail: christopher[dot]hogg[at]virgin[dot]net

On Fri, 15 Aug 2008 21:56:01 +0100, Chewbacca 
wrote:


>Just a thought, but fridges are tall boxes, and if left to stabilise I
>would expect quite a large temperature gradient, ie the top (where you
>keep the butter etc) being a fair bit warmer than the bottom.
>
>Where did you put your sensor?
>Try near the bottom and see what you get.
>
>I would also think that there is a fair bit of hysteresis (can't spell)
>so put the sensor in a lump of something (tomato?) to average out the
>variation and see what you get.

Thermometer and thermocouple were on top of the salad drawer, where
the user handbook recommends test temps should be measured. T/C in
free air, but thermometer in a cup of water. Both read almost exactly
the same the following morning. But thanks for the thought.

-- 
 
Chris

E-mail: christopher[dot]hogg[at]virgin[dot]net

On Aug 16, 10:56 pm, Chris Hogg  wrote:
> On Fri, 15 Aug 2008 15:57:10 -0700 (PDT), meow2...@care2.com wrote:
> >Could probably be fixed with a resistor, but you'd need to show us the
> >circuit diagram.
>
> >NT
>
> I wish....

ok then, it can be done without it. You need to find the measuring
device, I dont know if it'll be a thermistor or thermocouple, but...

If a thermistor, all one need do is add a little series resistance to
shift it one way (perhaps 2-4% of its R) or a lot of parallel R to
shift it the other way (maybe 25-50x R_thermistor).

If its a thermocouple you really will need to get to the circuit and
trace at least the first part of it out.


NT

Try the forum on UKwhitegoods (google).

Might be a 'known problem'

cheers,
Pete.

On Sat, 16 Aug 2008 18:02:25 -0700 (PDT), meow2222@care2.com wrote:

>On Aug 16, 10:56 pm, Chris Hogg  wrote:
>> On Fri, 15 Aug 2008 15:57:10 -0700 (PDT), meow2...@care2.com wrote:
>> >Could probably be fixed with a resistor, but you'd need to show us the
>> >circuit diagram.
>>
>> >NT
>>
>> I wish....
>
>ok then, it can be done without it. You need to find the measuring
>device, I dont know if it'll be a thermistor or thermocouple, but...
>
>If a thermistor, all one need do is add a little series resistance to
>shift it one way (perhaps 2-4% of its R) or a lot of parallel R to
>shift it the other way (maybe 25-50x R_thermistor).
>
>If its a thermocouple you really will need to get to the circuit and
>trace at least the first part of it out.
>
>
>NT
OK, thanks, but I'll have to find my way into the works first! I was
really hoping someone could tell me where I could find the trimmer pot
that I assume exists for calibrating these devices. After all, an oven
t/stat has an adjusting screw (probably a different mechanism, I
know), as do older style fridge t/stats, so I presume this electronic
thermostat has something broadly similar.

-- 
 
Chris

E-mail: christopher[dot]hogg[at]virgin[dot]net

On Sun, 17 Aug 2008 02:42:36 -0700 (PDT), Pete C ukdiy
 wrote:

>
>Try the forum on UKwhitegoods (google).
>
>Might be a 'known problem'
>
>cheers,
>Pete.

Wasn't aware of it. Good suggestion. Thank you.

-- 
 
Chris

E-mail: christopher[dot]hogg[at]virgin[dot]net