While there's no direct plug-and-play replacement for the Atwood GC10A-4E with a gas-only tankless unit, you can upgrade to dual-fuel tankless heaters like the Girard GSWH-2 or Truma AquaGo. These maintain electric capability while providing instant hot water and better efficiency.
Girard GG1000 motion sensor can usually be disabled by pressing and holding the extend button for 5+ seconds after fully extending. This allows use of support poles and sun shades. Re-enable by holding retract button when done.
Girard II tankless requires different wiring than DSI tank heater. Run new 10 gauge 12V power with 30A fuse. Do not reuse old DSI harness. Follow Girard diagram exactly for proper operation.
Tankless RV water heaters lose significant efficiency at high altitude - about 4% per 1,000 feet. Above 4,500 feet, expect reduced output and possible flame failure. Consider traditional tank heaters if you frequently camp in mountains.
Everything you need to know about RV plumbing systems from fresh water supply to waste management.