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If it was my reefer - figuring about 25-30 year normal reefer life, and $1000+ replacement cost, I definitely would be fixing/replacing the icemaker. Most likely just a bad seal or leaking water dispenser valve casuing icing up, for less than $25 parts and maybe $70-125 labor - even the entire unit needs replacement it would probably not cost much more than $250 ballpark. These units are made as add-on units in most cases for addition to reefers that came without one, so just a few bolts, an electrical connector or two, and hooking the water line back up - so not a major work item - probably usually less than 1 hour labor.
