Is this "flue" system [not "vent" IMO] original equipment on your 1968
, and does your owner's manual have any guidance?
Our old 1985 Sovereign
25' had a similar system, and I don't think we even had a fan in the "flue" system, because the heat of the propane flame and electric heating element created enough up-draft to get the hot air up and out through the roof.
"fridge roof flue site:airforums.com" search results FYI:
If there is sufficient ambient intake air through the exterior [presumably louvered] door, no fan should be necessary IMO.
But why leave the trailer for that long with the fridge on? Aren't there safer and less costly alternatives?
The odds of some kind of electrical etc. failure are probably close to zero percent, but why risk any
damage over months of absence?