Not sure if this will help anyone but wanted to post my Suburban IW60 install experience. I want to preface by saying I'm pretty handy but an amateur when it comes to this stuff.
I started with the standard Suburban 6 gallon water heater but wanted to upgrade it. I disconnected the 6 gallon which has two electrical connections, one for electric and one for just propane. The electric connection is just as you would find in your house plug in, 12VAC. The gas side is the 12VDC electrical connection. Since the IW60 only works on propane the plug connection or 12VAC is not needed for this install. The water connections were pretty easy and straight forward. The electrical side was the one that gave me extra grey hairs! I'v posted some pics that I hope will help but you shouldn't rely on the colors matching your RV, just the concept of the current flow. You will notice you have 6 wires coming from the IW60:
Black (-)12VDC
Red (+) 12VDC
Blue and Orange - For a lamp connection
White - 2 white lines for the On Demand Control Center
After taking out the 6 gallon I had these wires left over:
Black (+)12VAC
White (-)12VAC
Blue (+) 12VDC
Green/White (-)12VDC - this is a multi-colored wire
White (+)12VDC - this wire was connected to the Green/white(as in photo)
This is where you will need to use your multi-meter to determine what you have. First off you can eliminate the 12VAC lines used for the 6 gallon as the IW60 only uses 12VDC. On my control panel for the RV I have a switch for a water heater, connected to this switch was a Blue (+)12DC wire. I connected this wire to the Red (+)12VDC wire on the IW60. This will allow you to turn the IW60 off and on by flipping the switch on your control panel. I did have another wire Green/White(-)12VDC and White(+)12VDC. I connected the Green/White (-)12VDC to the IW60 Black (-)12VDC. The white (+)12VDC I left open and unused. Though I didn't try it I would assume you could use this for your (+)12VDC connection but the unit would remain on all the time. By connecting to my switch panel it was not necessary and I thought it better to be able to switch off and on as needed. So now we are down to 4 wires left open on the IW60. The Blue and Orange lamp wires were not needed for me as I used the panel lamp/switch. The two White wires go to the Control Center. This completed my wiring connections. I want to say it was easy but the difficult and time consuming part is determining what wires are what. This is where the muli-meter came in handy. I attached some photos as well. Hope it helps! Dave