Where is the defrost timer located on GE model# GSS20IEMDWW side by side refrigerator? My freezer works but the other side is warm. I took the freezer panel off and it had a thick layer of frost everywhere. Possible defrost timer issue?

This model does not have a defrost timer. It has a motherboard. You must jump out the plug to the main board to test the defrost circuit. In order to do this take the cover off of the main board, find the three wire connector on the base of the main board, connecter is normally blue in color. On the board itself it will identify termials as line, defrost, and compressor. To test you must create a jumper wire.Install the jumper in the plug terminals identified as line and defrost.This will turn the defrost heater on. If the heater does not come on, look for a defective heater or a defrost thermostat(mounted on the top of the evaporator). If the heater does come on replace the thermister(located on top of evap, white in color and has two white wires part#WR55x10025)