I believe your understanding is on the right track.
Originally Posted by Flying Pig
Hope these help!
The best I can tell the D + signal is attached to the ignition circuit for the engine. The high current supply would be to run the refrigerator say off of the battery bank or the alternator in the low current supply would be strictly from battery power when running propaneÖ I just want to make sure I have a good beard on this before I burn a hole in a $1200 refrigerator!
Yes, the attached photos did help.
According to the documentation page, the D+ is indeed used to control the use of the 12V DC high-current input so that the battery is not drained by the refrigerator while the engine is not running. Bear in mind that this would mean the refrigerator is NOT running when the engine is turned off ... unless hooked up to the AC power input or propane ... but the low-current power input is still needed in these cases as well. I could not see where the D+ signal come into the wiring diagram ... which is really a block diagram at best.
One thing to note is that the low-current lead is to run the electronics in ANY/ALL modes. All of the push buttons and switching is powered by the low-current DC input.