Voltage drop at ballast resistor

Mattax said
Lets do this step by step.
Use this diagram or make one like it. Make copies and write on it.

Recharge the battery on a charger.
* For your own education, measure the voltage across the battery while charging.
Remove charger.
* Measure Voltage at Battery Positive, Alternator Output (Bat), and Bulkhead at Red Battery, Black Alt, Blue Run.

Turn Ignition Switch to RUN.
* Note current flow through Ammeter. Should be around 5 amps discharging (3-4 to alternator field, 1-2 to coil and ECU).
* Measure Voltage at Battery Positive, Alternator Output (Bat), Red Battery at Starter Relay, and Bulkhead at Red Battery, Black Alt, Blue Run.
* Recheck Voltage at Battery Positive.
* Observe ammeter. Write down any change from first turning on ignition.
Turn Ignition switch OFF.

View attachment 1715165636

OK, here's what I think I found.
Recharge the battery on a charger.
* For your own education, measure the voltage across the battery while charging. (13.24 volts)
My cars stay on a trickle charger all the time.

* Measure Voltage at Battery Positive (13.04 volts) *, Alternator Output (Bat) (12.96 volts), and Bulkhead at Red Battery (12.88 volts), Black Alt, (1.4 volts) Blue Run. (0 volts)

Turn Ignition Switch to RUN.
* Note current flow through Ammeter. Should be around 5 amps discharging (3-4 to alternator field, 1-2 to coil and ECU). (Yes I'd say 5 amps)

* Measure Voltage at Battery Positive, (12.10 volts) Alternator Output (Bat), (11.12 volts) Red Battery at Starter Relay, (12.22 volts) and Bulkhead at Red Battery, (11.81 volts) Black Alt, (11.47 volts) Blue Run (10.47 volts).

* Recheck Voltage at Battery Positive.* Observe ammeter. Write down any change from first turning on ignition. (No noticeable change)
Additionally I checked voltage at the back of the amp gage and it was 11.47 at both post.

While under the dash I sprayed contact cleaner into the bulkhead connector.

After I completed all the test, I checked the voltage at the blue wire on the resistor. It was 10.47. It is now 9.58. WTF???

Also I noticed the red wire at the bulkhead under the dash gets noticeably warm while making these test.

These numbers seem all over the map to me but with 3 back surgeries they are the best I can do.