Charging system
I checked voltage at the firewall connector and it was 11. Something volts. Plugged in the connector and checked voltage at the blue field wire at the alternator and it read 9 volts. I wil replace the wire from the connector to the alternator and hopefully it will fix the problem
It won't. You must troubleshoot with all connections in place. When you disconnected the wire, you lightened the load (current, amperage) on that circuit, so the voltage went up through werever the bad connection is.
The "entire path" is generally as follows, and the drop could be any one or more than one point
From battery to the starter relay "big stud" through the FUSE LINK, through the BULKHEAD CONNECTOR via the BIG RED ammeter wire, to the AMMETER, through it and out on the BIG BLACK ammeter wire, to the WELDED SPLICE which is a few inches from the ammeter, under the dash.
The WELDED SPLICE branches off and feeds power to the IGNITION SWITCH, through the SWITCH CONNECTOR, SWITCH, back out the SWITCH CONNECTOR on the (usually blue) IGN1 ignition feed.
That wire feeds back into the engine bay through the BULKHEAD CONNECTOR and branches off to feed the ignition ballast, VR, blue field wire, etc
ANY ONE of the capitalized points can be a drop. You need to "chase it back" to find it
As I said earlier, adding a relay can help in most cases
