Actually most of your appliances have control boards. The refer, hot water heater, furnace, etc. These are used to control the operation of each appliance.
The refer is cooled either by AC or LP. When one is having a problem with cooling it is hard to tell if the cooling unit is defective or the control board. Bypassing is done by turning off the power and disconnecting the AC leads to the heater element. By appying AC directly to those leads you can tell where the problem might lie. If your freezer gets to the 0 degree range then the cooling uint is probably OK. If it doesn't then the cooling unit needs replacing.
We have a Norcold 4 door refer. I disconnect the AC and turn off the refer. I then remove the AC leads to the heater that are attached to the control board. They are yellow and black, two each. Dometic refers may be a little different as to color and number. I connect both yellow leads to one side of a power cable and the black to the other. Then I plug that into the outlet for the refer. The control board is now off and only the AC is attached to the leads. You won't have any ice maker operation and the light will be out in the refer.
After several hours if the temp hasn't come down you'll probably have to replace the cooling unit. A note on Norcold 4 doors... you can do the same thing by disconnecting the connector at the light inside the refer. This is also the sensor to the control panel. That will force the refer into max cooling. I found that out after I went through the disconnect process several times!
In your case of losing power you can do the same thing to keep the refer cold. Just be careful when hooking up the power so you don't get shocked. It appears my problem is the fans. I now have the freezer at 0 with the control board in the circuit. I placed a fan at the access panel outside. Once I got the freezer down to temp I disconnected the direct AC input and inserted the control board. It has been maintaining near 0 for several hours. Guess I'll be talking to the techs about accessing the fans. Unfortunately it appears we have to remove the refer from the wall to get to them. Now you know why I hate to give up my part time job at the dealership. ;D ;D
Hope this didn't confuse anyone too much.