When I was unable to travel south in the winter, I would use the low point drains on my 5er, then blow the lines with compressed air, THEN circulate RV ,A/F through the water system, using the 12 volt pump ( to minimize dilution of the A/F for maximum protection) When you know the RV will be sitting at temps as low as -45 you don't take any chances.
Do you have the owners manuals for the fridge ( ice maker ) and the combo unit , winterizing should be detailed in both manuals.
If you don't have the manuals , maybe we can find a pdf for you.
Can you post the brand and model numbers.