Maytag Frig not cooling but freezer is cold

[bigzinmiami]

Noticed in the past week that the refrigerator is not getting really cold.

Did find the cooling coils were dirty, so cleaned the entire mechanical section with a vacuum and compressed air to blow all the dust and crud out.  

The condenser fan and the fan in the freezer run.    The freezer is cold, but the heat exchanger in the freezer had frost on all the tubing, but not frozen solid though so air is flowing inside the freezer compartment.

Followed the duct up to the top of the fridge side and sliding the temp control all the way to coldest and didn't feel too much cold air coming out (maybe that's normal).

What other diagnostics can I do?  How do I know the defrost mode is working?  And should the cooling coils inside the freezer be frosted over in any manner?   Is it possible there is a blockage in the ducting that goes to the fridge side?  

I am fearing in another day or so, I will start losing food and have to call a repairman.

Model MSD2756GEW

[JWWebster]

Could be a defrost problem. Check this out:

[bigzinmiami]

Thanks, the evaporator coil was frozen over, so I used a blow dryer and melted all the ice.   I pulled the plug on the heating element which has the defrost thermostat attached to it and checked the resistance.

For the heating element, it showed about 20 ohms.   The defrost thermostat showed 240 ohms, as specified in the wiring diagram.

My thought is the adaptive defrost board and/or the temp control, the next things in the electrical path. 

Would prefer not to spend $80 for a defrost board unless it is necessary.   Any diagnostic for that?

When I turn the freezer temp control to off, compressor and all fans go off, so at least that much of the temp control works.

The unit has always frosted over food in the fridge for a long time, but at least it got cold.

Maybe replacing both parts is the safe thing to do?

[JWWebster]

If the terminator(defrost thermostat) and the heater check good then the defrost board would have to be it or the defrost control's connection might be corroded.

[bigzinmiami]

Replaced the "adaptive control board", i.e. the defrost control circuit.   

I adjusted the refrigerator temperature to max cold, and did notice that the cold air flow from the freezer section is coming out of the duct.

Should the air flow change depending on the adjustment, i.e. is it a flapper control in the duct, or strictly an electrical control?

How long should I let it cool to know if it is working or not?  The fridge is full of "cooled" food, so I know it is a lot of mass to cool down.   Any other way to be certain this is working other than checking the evaporator coil at some point for freezing again??

[JWWebster]

Put it all back and wait 24 hours and see if she is all kosher again. It takes weeks for all that frost to build on them coils.

[bigzinmiami]

Thanks.   Overnight everything cooled down fine.  I had the same thoughts on the frost, it doesn't happen overnight so will wait and see if it comes up again.