Whirlpool electronic thermostat for freezer

[MBfreak]

Hi.
My sons IKEA rebranded fridge/freezer gave up life. Thermostat faulty.
Overengineered electronic type.
IKEA has no info/spares, " 12 years old"
No Whirlpool original tags left.
Used the IKEA barcode number on WP site, no result. Not recognized.
Does anybody have a schematic or tips where to find.
Searched Whirlpool, BAMA, SAMS. Nothing.
Pics attached


Thanks in advance

Ola

 

[MBfreak]

Re: Whirlpool electronic thermostat for freezer. Bump

Many views but no feedback, so I guess it is a lost case?
Does Whirlpool still exist as a brand.
All info I find is quite old and the links to service info, probably just user manuals seem to be dead?

Time to fess up and buy a new fridge/freezer.
But since i am a fan of the repair lifestyle so well documented by Crawford in Shop Class as Soulcraft, I WANT to repair the unit.
Came halfway , simulated the output of the ATMEGA CPU and the relaydrivers, power supplies and fan and compressor start control all works.
But the CPU seems to be dead, or at least stalled .

Ola

 

[American Locomotive]

Whirpool exists. The board is likely doing a few other things, like managing defrost cycles as well. Usually what fails on boards like these are the capacitors. Try replacing the capacitors.

 

[MBfreak]

AmLoco

Tho Whirlpool is a fairly basic fridge freezer with no autodefrost.
There is one sensor only, monitoring the freezer temp and controls the compressor with that single input. ( NTC resistor)
I have already replaced the 5 std electrolytics on the board, even though the 5 originals were all around 10 % over nameplate data, after 12 years.
Interesting enough these caps are // with a small value tantal.
The board has a reed relay that controls the fridge light, and also a low voltage output that switches on the fan thru a semicondutor triggered from one of the outputs on the ATMEGA. That works OK.
The other ATMEGA output is not responding to sensor input within the set range.
Tried with a DC input 0-5 v and full setting range of the on board pot. The I/O channel driving the relay transistors stays at 0V. fan switched on/off as expected
Lifted the resistor to the first compressor transistor base and triggered from there with a 4,5 V signal. Relay operated.
So case closed now, even w/o scjematics. One output channel from the CPU runs the fan correctly ( fan ***** from freezer up to fridge ) The other channel that runs the compressor relay is not responding to inputs.

So a case for the bin, ( although I could fix it with a tweak!) A new processor, blank is dirt cheap but must be programmed. which requires program as well as hardware. NoGo

So will try to buy a new board, found one at $160. No go.

Ola

 

[Worsedog]

Or you could over complicate it with an Arduino to run it all.

 

[fitter30]

I've found most appliance parts are made for multiple products. Have you just googled the part numbers or taken them into a parts house? Maybe ebay in the usa even though yours is 50 cycle.

 

[walta]

If the boards only function is to turn off the compressor and condenser fan when the freezer gets to cold a PID controller and relay like this one should be able to handle the job at a low cost.

https://www.ebay.com/itm/Digital-PI...482647?hash=item260c33dc97:g:uv4AAOSwbmFccLzw

Walta

 

[MBfreak]

Thanks for all replies.
Fault is in CPU , an ATMEL part.
Found a supplier in Italy, around $145 including freight.
I have now built a simple analog controller with an opamp, schmitt-trigger and output relay.
Will use original board for potentiometer temp setting and power supply.
Cost all of $15.
I am VERY much in favor of numerical solutions but as a simple thermostat think it is a gross overcomplication!

Ola

 

[rlitman]

A smart thermostat would protect you from short cycling or freezing up.

 

[SGKent]

you are in Sweden, and you are running 220 - 240 VAC. Here in North America we run 120 VAC for consumer household products like refrigerators. It is unlikely a part like this would be found in any American or Canadian parts house. You would have to look around Europe. That said you indicate that you built your own so that is a good solution.

Were it me - I might have guessed that one of the blue devices is a fuse or thermal fuse, or there is one on the power supply for that board. Diodes can be prone to failure too.

 

[MBfreak]

Guys.
I have been designing, building and repairing electronics for a long time.
The fault is located ( DO pin on the ATMEGA CPU), but it is not economically feasible to buy a blank CPU and then program and the board we found costed around 30 % of a similar fridge/freezer.
I will tweak a simple NTC input analog circuit to replace the board, the cooling circuit works perfect. Minus 22 C in freeezer and +6 in fridge.
My son, who is even more stingy than I will wait for a sales drive with lower prices on a new unit.
Case closed.

Bets regards