Did you try unplugging thermistor and checking if fridge would cool down?
Does it cool down using propane?
YES the Alarm is because you bypassed the circuit board
When you directly wire the AC Element it is energized continuously
Run it that way for 12HRS........if cooling unit is capable of cooling the food compartment should get cold enough to freeze food items (careful if you have canned sodas/beer etc)
IF fridge cools down then either the thermistor (temp sensor) is bad or the circuit board is bad
Make sure the external fan(s) are running
*thermostat for fan is connected to far right FIN on condenser unit at top of fridge (accessible via top sidewall vent cover)
thermostat closes at 130*F FIN temp to aid in airflow/draft across condenser. Opens at 115*F
If not running could be part of issue also