Atwood water heater?????

Above posts are good starting points.

Water Heater 'Bypass' Valve open or leaking thru.
Connects WH Tank Cold inlet line to WH Tank Hot outlet line.....cold diluting hot out making it luke warm

Showers not turned off via cold/hot knobs but just with button on shower head handle....allows cold/hot mixing inside shower faucet making luke warm water


Your Atwood is gas only model with electronic ignition.
T-stat controls heating cycles.....140*F t-stat opens --closes at 110*F to reheat

ECO (Energy Cut Off---Hi temp t-stat) 180*F opens to shut down heating should Normal T-stat fail. Locks out heating and triggers RED Fault Light. ECO closes at 150*F but heating circuit has to be 'reset' by turning ON/OFF Switch OFF--Wait 30 seconds then back ON

T&P Relief Valve is last safety should t-stat & ECO fail. Opens at 210*F/150 PSI and will BLOW hot water/steam out of valve.
Turn Switch OFF, pull the DC Fuse for water heater, valve out propane....but shut it down should T&P Open

Make sure your outside shower valves are off...not just the button on the spray head, but the valves themselves...

The linked video is of the outboard end of the water heater. On the inboard end, are bypass valves. These allow you to isolate the water heater from your plumbing. Then you simply drain the tank for winterizing, then pump pink antifreeze through the rest of the plumbing. If those valves aren't set right, water bypasses the heater and isn't warmed. Also, if you have any "mixing" fixtures, like indoor and outdoor shower heads, they can't be simply turned off at the head. The Valves have to be off, or hot water will mix with cold and give you lukewarm.

The thermostats are not adjustable on standard Atwood water heater.
Verify that your winterizing valves are in the correct postion if equipped.