frigerator section not cooling

[lbr4u]

The frig section was not cooling-upon taking this apart the back panel was frosted in the freezer. Checked the defrost timer after the first click the compressor shuts off. About 30 minutes later the timer clicks again and the compressor starts working. Put the timer back in defrost mode and checked voltage across the defrost thermostat and had 120v on both sides. Checked voltage on the heater element and had 120v on the thermostat side but no voltage on the other side. On unplugging the side with no voltage on it; I now have 120v on that (on both sides now). This is a bottom Freezer. Any help is appreaciated. Thanks