Good.
I've put this on the drawing...
They're fine. Lets look at what they show.
12.1 Volts at the battery under a 5 amp load. OK. especially seeing the next reading down the line.
12.2 Volts at Starter Relay.
11.8 Volts at Bulkhead. 0.4 Volt drop in the wire is a lot. If real, could be a bad crimp connection at either end or the fusible link splice, (corroded or broken strands ).
11.5 Volts on both sides of the Ammeter and at the Alternator connection. No loss to speak of from the battery wire to the main splice. (Since there is no load and no current in the black wire to the alternator - it can not be assumed the alternator's bulkhead connection is good.)
10.5 Volts at Run. Must be resistance between the main splice and this connection.
Sounds like a loose connection or a wire with bad insulation. Is the red wire is the one from the main splice to the ignition switch?
If that's warm with just 5 amps, that's a major problem.
View attachment 1715165781
