If the OP model# is correct, his PCB is located in the lower left rear corner looking from the front. We have same model. It might be easy to determine if the compressor is running by watching the amp draw. The wattage can be monitored at the digital display of the inverter which alternately shows battery input DC volts, then output kilowatts. In the image attached, mine shows 50 watts so the compressor is not running. With the compressor running, it shows 120-140 watts. If the compressor is running and both sections (refrig & freez) are warm, then there is a sealed system issue - Freon leak, restricted drier or cap tube or very low capacity compressor. I'll mention that blocking a large piece of 3/4" plywood up on boards to the same level as the shelf the refrigerator sits on is a good way to pull out the unit for service. It's a tight fit on our 3791 to get it turned so I can fit behind it.
