I've been in the RV business going on 24 years now (parts & service). Do you know what RV stands for? Ruined Vacation
There are very, very few RV manufacturers who actually produce a wiring diagram, plumbing schematic, etc. Winnebago and Airstream are two who seem to know what they are doing. Almost every other RV builder simply assembles their rigs from components they got the best deal on that day. It is not uncommon for an RV to be less than a year old, and already have parts that are no longer available, since most RV builders don't actually build anything in their factories; they simply assemble them from parts supplied by other vendors. Those vendors come and go, and there might be running changes on the assembly line, and then the OEM doesn't log that change anywhere, and it's anyone's best guess what part they actually used on that rig.
I had a customer come into our Keystone and Forest River dealership asking for a plumbing schematic for his 10 year old coach. He got rather upset because he assumed I was lying to him that we didn't have access to anything like that. He assumed that as a dealer, we should have that kind of information. I sure wish we did! Keystone is getting much, much better, using color coded wiring and such, but that only applies to recently built units.
Oftentimes when I need to order a part, I have to take a picture of the item and then email the OEM and say, "Send me this!" Then I cross my fingers, since there is a 50/50 chance they will still send me the wrong item after waiting 4 - 6 weeks.
If you want a specific non-appliance part for an RV built more than 10 to 15 years ago.... good luck. It's either unavailable, or the OEM didn't have computer systems keeping track of what they built! Or that OEM has been purchased by another company, and all records were lost. Can you imagine walking into a Chevy dealership and asking for a widget for your 2009 2500HD, only to be told it's been discontinued and is no longer available?
I still love the RV lifestyle, but the industry as a whole has a got a LONG way to go to keep up with consumer demands and expectations. It's gotten so bad, I'm really contemplating getting out of the industry altogether, since every day leads to a new frustration.
Casey