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.
To fix parasitic power draw through your 2006 Damon Challenger's instrument cluster, use a multimeter to isolate the circuit, check common culprits like clock memory and sensor wiring, and find alternative wiring diagrams through Freightliner chassis documentation or aftermarket sources.
Engine replacement for Thor Challenger runs 8000-15000 complete. Jasper or Ford reman engines recommended. Get experienced RV shop quotes.