By pure luck... I happen to have the water heater out of 2004 T317SR project camper which is undergoing restoration for some heavy water damage. This camper was built in June 2003. As such, it did not receive the Atwood design upgrade in 2003 for combo gas & electric water heater. Most likely both Sunline and the Atwood warehouses may have had a qty of old stock to use up, as I have other 2004 model campers built in Sept 2003 and beyond that have the new upgraded design.
Your camper being a 2001 model, more than likely had the exact same water heater, the pre-2003 combo gas & electric as I am going to show here.
Here is the model number and what the heater would look like from the outside behind the white drop down door.
The overall view of the gas valve and the gas control system.
The gas DSI control board.
The 3 wires that run the all gas DSI part of the water heater. A + 12 volts, - 12 volts and an ignition fault signal wire.
If you could, please repeat those 3 same pics above of your water heater (expect the model sticker) if you want me to dig up the replacement tank/parts. I suspect your current water heater was made after the Atwood sale to Dometic a few years back. I need to see and make sure Dometic did not change something that does not show up in the Atwood service manuals.
Now to the back side of the water heater where the electric element and controls are. This is what your original water heater would of looked like, and we can see what you are missing as far as the electric element controls.
The overall back side of the heater with the silver electrical box cover on. There is a small black on/off rocker switch in the silver cover to turn thge electric element system on and off.
The instruction label on the back with a wiring diagram.
The silver electrical cover off, step 1. There is a black insulation board cover the electrical connections behind it.
Removing the black insulation board cover. This shows the electric element, the thermostat thermal disk switch and the high temp shut off thermal disk switch known as the ECO (emergency cut off). You are missing the all these parts plus the metal plate that would hold these to the tank.
Here is a close up of the high temp shut off thermal disk switch (the ECO). It is a safety switch in case the system never shuts off. There is a reset button in the middle of it that needs to be pressed if it ever trips out. When this trips, an over-temp occurred and will kill the 120 VAC power to the electric element until it is manually reset.
As I was saying earlier, the pre 2003 configuration has a completely separate electric element and controls system. When you flipped the little black rocker switch on the silver cover, it turned on 120 VAC power to the system. The T stat would then control the electric element and start heating. This is all totally independent of the LP gas controls on the outside.
The new 2003 design upgrade uses a new PC board that runs both the LP gas and the electric element. You still need to supply 120 VAC, but a control relay turns the element on and off signaled from the control board on the outside. This made life easier for the camper owners as a 3rd switch was added to the KIB tank panel to turn on the electric element. Before, they use to have to crawl into the back of the water heater to turn the little black switch on and off. That got old real quick, and many folks with this vintage either flip the 120 VAC circuit breaker off, or they installed their own separate wall switch easily accessible to turn the 120 AC power on.
Also please confirm, is your LP gas on/off switch part of the KIB tank level monitor system? It would look like this. Just 2 red rocker switches, one for the water pump, the other to turn on the LP gas portion of the water heater.
Sunline changed the brand of the tank monitors over the years, and I do not know which year they switched to the KIB brand.
Let me know what you want to do.
Hope this helps