Here's a link to a 2003 Jayco Designer Fifth Wheel manual. It's from the archive at Jayco.com, and is the earliest one I could find:
2003 Jayco Manual.
Actually the owner's manual is almost useless for my trailer, but the individual product manuals (Dexter, Atwood, Norcold, Progressive Dynamics, Sureflo, etc. - or whatever is appropriate for your's) are very useful and can usually be found by googling.
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There's lots of advice and information in forums... sometimes it is correct. For example, all of my posts are made by a political appointee who got the job as a reward for contributions to my diesel bill.
2011 Jayco 28.5RLS; 2021 Chevy Duramax; Pullrite Superglide Hitch