that is a nasty splice.
continuity won't be the issue. it will be resistance causing the voltage drop.
but it sounds like it is past that splice anyway.
you probably don't have the extra line in that splice, but the old school way was to put ring connectors on them and put it on the big cable side of the starter relay. but I guess leave it alone if it ain't broke.
I have seen several factory splices on mopars done exactly that way and they were ALWAYS soldered.
in the second picture on the R side I note several corroded male terminals. Those should all be cleaned as well as the others.
I would also clean the female terminals and try closing them a bit with a small flat blade. If they are easily accessible from the backside you can remove them ne at a time for cleaning and then gently squeeze each side to insure a better connection.
I checked the voltage of the wire in the bulkhead running from the splice with the key ON and it reads 11.3v(firewall side) while the battery reads 12.6v... The voltage of the same wire at the bulkhead on the inside with the key ON reads the same (11.3v)!
the above statement is not clear to me ? I'm assuming this is with the bulkhead plugged together?
I am also assuming this wire is coming from the battery towards the splice
What is the V at the splice itself ?
if it is also 11.3 work back towards to battery.
Your statement indicates a 1.3V drop which is HUGE unless there is a draw pulling the V down or a bad connection not allowing the current to pass thereby causing the V drop.
Run a jumper across the two connections and see what the voltage does. The jumper can run from the splice to where ever the firewall side wire goes. If it goes multiple places the one closest to the BH would be best.
DO monitor the battery voltage while doing these tests.
