Water Heater question first timer.

[MartyG]

Originally Posted by sundancer 87

Then where is the flame sensor wire? For many years all I've seen for DSI ignition is a much larger red wire for ignition.

Here is a diagram of two 6-gallon water heaters made by Atwood. You will see that the diagram on the right exactly duplicates the OP's.
The one on the left is gas-only, no electric. It has some sort of a "pilot-relight" feature with a spark assembly. On my 2013 Coleman, it was even older, I had to push the red button on the valve in and hold it while lighting the pilot manually.
The diagram on the right is a gas/electric model, with automatic spark. The high voltage tower and porcelain insulator above the burn tube indicates that is a spark wire.
The Atwood owner's manual is a little strange, in that there are several diagrams without legends to the points numbered. Also, for a beginner, who has trouble with winterizing and valves, this is of no use. Written from just a water heater manufacturer's perspective, they just say that for winterizing, drain and flush (with air or water) the residual water at the bottom. As if it stands alone, and is not connected to an RV!

[sundancer 87]

Nice diagram, clear as mud as they say. I appreciate your effort, really do. It's not my heater so I can't say one way or the other. The only way to be sure of anything is to put an eyeball on it and check it out but that's not going to happen.

I suppose the next suggestion to the OP would be to throw the gas switch and listen for the ignition spark. That would tell the tale of DSI or not.

I take it the electric element access is from the front side since nothing is apparent from the photos.

I've had some pretty old water heaters over the years of living in a solar house so there is always the one that I didn't get a chance to swipe from the RV junk yard. I have taken these things down to the bones to have a tank welded, modified the electronics from a water heater to work on an old Dometic refrigerator and even built my own spark ignition when the junk yard was far away. I fixed one teeny tiny seeping leak with Bars Radiator Leak once.