Tell me more about this umbilical
Here's a link to a 7 pin which you should have on the coach end, at least...
WiringWhether or not you have a spare on the toad end, I can't be sure, but an alternative is to just wire tie an extra run of #12, alongside the umbilical and attach a separate one pin connector on each end.
I did this once on a factory cable that I didn't want to change out and for running a dash indicator light, telling me when the toad brakes were being supplied.
In your case, the coach end would then run to the chassis battery with an inline fuse attached at the pos terminal and the same for the toad's battery.
