Several things here… you have a 3 year warranty on your fridge, and it seems you have a 2012 trailer…
If you are the original purchaser you have a three year warranty on your fridge… so is it still under warranty???
The 3 rear warranty covers parts and freight with 2 years on labor…
The cooling unit is a covered part for the 3 years, meaning labor should be your only cost at the dealer… while I have never personally replaced a cooling unit I understand they are not hard to do yourself and shouldn’t take to many hours in labor at a dealer…
Is there a chance this dealer isn’t being honest up front about the warranty and if so its time to find another repair facility…
EDIT: I wouldn’t agree it died from lack of use, no reason to believe that would happen… they are pretty reliable and can last for 50 years…
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Love my mass produced, entry level, built by Lazy American Workers, Hornet