9 Volts backprobing which wire terminal on the steering column connector?
10.5 Volts backprobing where in the engine bay?
Something garbled in the typing there!
I'll assume the measurement was from the battery positive to the alternator stud with output wire.
That shows there is a lot of resistance somewhere between the battery positive and the main splice.
View attachment 1715733810
To narrow that down further, move the probe to the starter relay connection, and then to the fusible link connection if its not sealed. I'm not sure what's on your car.
It would not surprise anyone if there was some deterioration in cavity 16 of the bulkhead connector, but sometimes its a bad connection at the battery cable or something else.
Let me be sure I understand. When the headlights were on, one probe on the top of the lead terminal and the other probe into the cable's terminal?
If so, the .4 Volts is a portion of 2.4 Volt drop between the battery and the main splice.
Because the resistance is at the lower limit of what most multimeter's can measure.
Resistance caused 2.4 volts to be lost when 12 amps was put through the line.
2.4 Volts divided by 12 amps
That's 0.2 Ohms
