We have a Whirlpool WRF989SDAW02 36 inch side by side fridge with the freezer drawer at the bottom. The fridge is not defrosting (evaporator? area, behind the freezer drawer)

I have already changed the heater and thermostat back there, to no avail. It takes about 3-5 weeks from the time I melt down the ice on the evaporator manually (hairdryer) until it is completely iced up again.

Does anyone know where the defrost timer is located on this fridge? It will be the next step, but just want to make sure I can get to it.

Thanks in advance.

Edited by user Friday, February 1, 2019 3:54:54 AM(UTC)  | Reason: Not specified