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All temp sensors shows incorrect values - Kenmore Refrigerator model 111.73025711

Zuy

Member
Joined
Aug 1, 2022
Messages
1
Location
USA
Model Number
111.73025711
Brand
Sears Kenmore
Age
1-5 years
Last weekend I noticed that freezer fan makes weird sound and temperature in the freezer raised to +5C.
Quick troubleshooting lead me to defrost heaters which were on for too long time enough to make freezer worm.
Disconnected both defrost heaters. Temperature slowly moved towards -13C but never was lower.
Trying to understand what is going on I found service manual and checked the values from all temp sensors.
They all show some weird values which has nothing in common with reality. For example:
F: -8.8C
R: -2C
FD: +20C
RD: +24C
IM: +0.5C
RT: +6.1C
Another thing I noticed is that every time I do power cycle for a whole fridge I see differently incorrect temp measurements.

Service manual says that main PCB has to be replaced. I found id on the back and first thing checked the resistance and behavior for all freezer temp sensors. They all are ok.
I traced the voltages on the F sensor route all the way to main MCU pin. For the temperature of -3C, impedance was around 9k which with another resistor of 25.4k made an voltage divider which provided 3.64v to MCU input pin.

For me it looks like sensors and measurement circuitry are ok but for some reason MCU still cannot measure temperature correctly.
Does anyone have an idea what can be wrong?
I do realize that replacing the main PCB would be the easiest option but the only one I could find was the used one on eBay. Is there any other place which would have main PCB for this fridge in stock?

The only error I see are F3 and r3 which are related to unable to complete defrost in 50min. Which is expected since I have defrost heaters disconnected.

Thank you.
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
132,461
Location
Redmond, Oregon
Hi,

Your Kenmore 111 model is made by Daewoo. Unfortunately we don't have any tech. data information on it.

Here's the threads on that model that others have posted:

Jake
 
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