B20CS81SNS/01 bosch freezer/fridge side by side is warm at top and cold at bottom

Check that the fan is operating. If the bottom of the fridge cold & the top warm then thats probably the issue.

check yor damper door, it's the little door at the top and or bottom of the fridge insid near the top and or at the bottom behind the crisper drawer when working right they open to let cold air in from the freezer and warm air out. top one cold in, bottom one warm air out.they work on a sensor/relay when the freezer fan goes on they open when cold air is needed.

Hi,
The unit is stuck on defrost....

Refrigerator not Cooling or Fridge not Cooling

How to Defrost Refrigerator Defrost Timer Problem

Water Running in refrigerator from Freezer

Refrigerator or Freezer not Cooling or Getting Cold

heatman101

3 things
If you have ice on the freezer side.
1. defrost timer not working
2. blower fan failed, if it has one
3. defrost limit switch failed..
i dont think it is #2 but 1 or 3
last but not least your defrost heat coil has failed

The door seals may be leaking but also make sure the drain is open.

Behind the back wall of the freezer about halfway down, probably behind the light bulb (if there is one there) there is a fan. My guess is that the fan isn't working, or is slow. To test, open the freezer door, then hold the door switch closed and listen for the fan.

This fan should be blowing air up the back of the freezer, and send some of the cold air through a vent at the top of the freezer into the fridge. The air then descends through the fridge and reenters the freezer through a vent at the bottom. If the fan is broken, or if the upper vent is somehow blocked or broken, the cold air will enter (rather than exit) the fridge side at the bottom vent. Because cold air tends to descend and warm air rises, the cold air will freeze the stuff at the bottom of the fridge, and the thermostat (at the top of the fridge) will say it is warm.

It is a thermostat problem. It can be fixed but is sometimes cheaper to buy a new one.

Thre is a fan inside the freezer which circulates the cold air around both the fridge and the freezer compartments.
You should be able to feel cold air blowing around the inside, particularly at the top of the freezer.
If the defrost thermostat fails open, the internal fan (depending on freezer) will stop and this can be the cause of the freezer being warm at the top and no ice.
You say the bottom of the freezer is blowing cold, but are you sure its blowing, as it can feel like a cold blow. Of course the fan could have failed or may be the defrost heater itself.
Have a look at this site for some useful trouble shooting
And a good site for troubleshooting and general info
Refrigeration Help Section, Fridges, refrigerators, not cold enough, frost free problems and how to test, noisy fan motors, clicking on and off compressors, door gaskets
Nige

CHECK TO SEE IF THE EVAPORATOR FAN MOTOR IS RUNNING, ITS IN THE BACK OF THE FREEZER SIDE, MOTOR MAY BE BAD OR SOMETHING COULD BE BLOCKING IT...

1. check the comp. working touch the top of the comp. 2.if the motor comp. working touch the high side tube of the motor comp. if to hot the freon is ok. 3. check the cooling fan inside.