mslovak hasn't been around here since his first & last post on June 13th, 2019. Doubtful he will reply.
Intervec was a van conversion shop rather than a full RV builder, but the difference may be academic. They've been out of business for ages, so no factory support available. If you can identify the appliances onboard, you may be able to find manuals for those online - just google the appliance brand and model. You can also get the van owner and service manuals - they are usually easy to find. Is it a Ford or a Dodge (Ram)?