Attwood water heater

The controls (wall switch) have numerous wires from the wall switch to the water heater. The Atwood control board on the water heater will not be your problem. IT has its own 2 to 3 amp fuse that protects circuits. So, the odds are the wires going from the wall switch to the water heater have grounded(shorted) out. You need to access the top of the water heater to see those wires. IF no access from inside, you may have to partially remove the Water Heater to check and make sure those wires are not pinched or shorted at the water heater. IF NOT, then work you way back from the W/H inside the RV to see where the wires run and if they are pinched. Has any work been done on the RV prior to this problem? Doug

Of this I am sure: It is not a burned out heating element. Here is why:
Heating element is protected by a circuit breaker, either 14 or 20 amps, it is not protected by a fuse and if it were 7.5 amps is no where near big enough since the element should draw 10-11 amps in normal operation.

Control board or short in and around it. OR short in leads to switch. Depending on where that 7.5 is.

DC fuse in dist. panel blows when you turn water heater on using propane....and evidence of hot spot on high tension wire to spark electrode.

Unplug wire from circuit board and try new fuse.
If it doesn't blow..then get new spark electrode wire assembly.

IF it still blows fuse....new circuit board AND new spark electrode wire assembly

Dinosaur Electronics replacement boards are better quality then OEM

AS a new memeber please fill out 'signature line' so your rv info posts AND provide Model of items you are looking for info on.
Lots of different Brands/Models so different resolutions
Norcold/Dometic/Suburban/Atwood numerous models of fridges/water heaters/furnaces etc. It helps vs 'guessing'

Maybe the heating element is burned out? in the water heater.