The blue alternator field wire ONLY is same as "switched ignition" This actually branches off from the ballast input coming from the key. This is a common " branch" point depending on year/ model. The key feeds "run" voltage out through the bulkhead and right there in that area going to the ballast it branches off and feeds
The coil ballast resistor
The alternator blue field
The VR "IGN" terminal
Electric choke if equipped
Idle solenoid if equipped
On some, the distributor retard solenoid
On a few cars some smog doo-dads
NONE of that is fused from OEM
