Weird temperature sensing behavior GE bottom mount PDS20MBRBWW

[iseeabird]

Hi all

For a week or so, the above mentionned refrigerator exhibits the following behavior:

• When the compressor is not running, or when the fridge has just been reset (unplug), the temperatures displayed by the fridge are OK, as confirmed by external temp probe
• When the fridge is running, the measured/displayed temp is +-5 F higher than the actual temp in the fridge

This causes the fridge to run colder than the settings and, when the settings is left at 37F, freeze the food slightly, since the actual temp when running reaches 32. Yes, I can set 39, but that only bypasses the problem.

So far I have confirmed the following:

• All fans run normally, regulated DC is good and stable at 13.5 V, evap fan runs at medium speed 170 tach per minute (at pin 1 on the motherboard fan connector)
• Global operation is otherwise normal, everything runs fine, defrost ok, I have not seen the damper operate but I can hear it
• Thermistors all seem good, they all read between 16 and 17komhs in ice water.
• The common DC voltage for thermistors is stable at 4.95V and does not differ between running and not; overall there is no electrical difference between running or not at the motherboard thermistor connection

At this point I am at a loss as to what to do next

• the problems seems to be between a faulty motherboard or faulty temperature control board
• does the temp control board actually do anything else then display and enter the setpoint?
• How can i pinpoint which of the 2 is the problem. I know the MB tends to heat up during operation, so I am leaning towards that side

Any thoughts?

[johntech]

You need to see the damper operate. It may not be closing and leaking air into refrigerator.