Solar Prep Kit
It is unlikely you will find a wiring diagram for your Aspen Trail. Dutchmen has not made them for consumers for a long time.
There may be a kit the dealer could install. Contact your dealer.
What is in the kit may inform what is in the solar prep option. I expect there is a junction box on the roof and a plug socket on the front passenger side. The wires may lead into the front pass through where a solar controller needs to be installed. Where ever the controller connection is, it is probably near the battery.
Be prepared, some dealers have no clue.
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