I have a Whirlpool Gold French Door Model GX5FHDXVQ00 with the bottom freezer. The issue is that ice builds up on the back wall. If it builds up enough the upper part of the frig is warm. I have cleaned dust off botttom of coils under the frig, checked that the drain isnt plugged with anything. When I have removed the back wall, there is ice all over the evaporator coils. I tested the heater and it ohms to the spec per the schematic. I have even gone into the service tests, performed a forced defrost and the heater is hot. So, I tested the thermostat at room temp and in a ice and my meter reads open. So, I purchase a new themostat it does the same thing. I even frozed it in a block of ice and it still reads 57K ohms. The thermostat spec shows it won't close until it gets to 12 degrees (+/- 10%). So how can the heater work and remove the ice build up if this range is soo low ? I am at a loss. Every so often I have to remove the back wall of the freezer and use a blow dryer to manually defrost. Can you please help me here ? Thank you.

I'm having the same problem. What is the "Jazz board"?

The jazz board is the circuit board located above the top shelf where the lights and the temperature management system where you adjust your temperatures for the frig and freezer. The board itself cost around $65 or so. I found it on ********. You will need to use your serial number to make sure you get the right one. Be careful removing that upper panel. There are instructions on this blog for removing this. Don't force, take your time and you will be successful. There may even be something on You Tube. Just google " replace jazz board in whirlpool refrigerator. Hope this helps.

PS Sorry for posting a competitive suppliers

Zmonicaz - I would follow the APP guys here. They also have videos. I have used them many times and they have been very helpful.