https://www.esscoaircraft.com/p-948-...rs-manual.aspx
http://www.ebay.com/itm/Cessna-ARC-N...-/380698999478
Robert, the last time I asked my radio shop to do some adjustments on my Navomatic 400 they asked me if it was working and I said yes and they said good, because we don't think we should touch it. These units are getting really old and most shops are shying away from them because they can't fix them after they touch them. Call Autopilots Central in OK, they are about the only guys that might be able to help you