Thermal switch on stack TRIPS from overheating...NO Auto Reset
When tripped ALL DC is secured
Your model uses a spark electrode to provide ignition of gas AND a thermocouple to prove flame is lit
Bad thermocouple, bad connections etc...no flame signal so circuit board dumps DC to gas valve
Gas Valve solenoid resistance
Remove the connectors from the solenoid and measure the resistance across the terminals.
The proper reading would be 49 ohms with tolerance range of ten percent.
Thermocouple millivolt readings
To check the flame sense circuit of the lower circuit board, operate the refrigerator on GAS mode, then measure the millivolts between J3 terminal and the other wire connection from the thermocouple.
The millivolt meter should read between 25 to 35 millivolts with the gas flame burning.
Any reading below 18 millivolts could cause erratic gas operation.
Thermocouple
Dometic 2932052018
Lowest price I have seenService Manual