The Onan 5500 can be tuned up with quality aftermarket parts when OEM parts are unavailable. Use NGK 3432 spark plugs, Wix 57358 oil filter (not 57398), and zinc-containing oils like Rotella T6 for optimal performance.
Heavy brackets stored under sofa are likely spare parts for slides, jacks, or furniture mounts. Photograph with measurements and post to RV forums for identification by your make/model.
The burnt spot with carbon buildup 18 inches from the end of your 2013 Thor Challenger's V10 Triton dipstick indicates the dipstick tube is allowing hot gases or oil to contact that specific area. This commonly occurs due to a cracked dipstick tube, worn O-ring seal, or internal engine pressure issues.
Post clear photos to brand-specific RV forums for identification. Check owners manual diagrams. Take to dealer service department. Common mystery items include antenna parts, winterizing fittings, and previous owner accessories. Keep unknown items - purpose often becomes clear later.
Common RV components with red lights include LP detector, CO detector, surge protector, and inverter. Red typically indicates fault or alarm. Check for model numbers to identify and post photo for specific help.