In the 915 install manual they show that the 12V source for the start power switch comes from pin 3 of the ECU X3 connector.

In that case fuse F2 is protecting the sourcing of 12V when the engine starts and the sink of alternator power after the engine is running,

I would like to use Vertical Power's Primary Power System (PPS).
In that case I believe I need to connect the PPS ALT pin to pin 3 on the ECU X3 connector.
That's where you send power back to the system busses/battery.

I would then connect the 12V source for the start power switch to fuse F1.
In this case fuse F2 only protects the output of the alternator and fuse F1 protects the sourcing of power to the ECU for both start and ground/emergency purposes.
However I am not sure if the PPS ALT pin can source any current. In that case pin 3 on the ECU X3 would not have any power on it at start.
Answering the following question might also help me to understand this part of the wiring.
If I only plan to use an external alternator, is there any reason I would connect anything to pin 3 of the ECU X3 connector ?
My understanding is that the ECU already internally selects the best power source ... so there should be no need to connect pin 2 and pin 3.
If nothing needs to be connected to pin 3 of the ECU X3 connector I think the wiring diagram would be easier to understand if they moved the source of the 12v for start power to fuse F1.
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