Thanks guys, I assumed it should be practically the same but wanted to make sure I wasn’t missing something.
I had no electrical issues, then my alternator stopped charging. Swapped regulators, no change. Installed an OEM single field round back alternator (should be 35 or 46 amp) and it charges about 20 amps at idle. Swapped VR back and still 20 amps at idle. Tried another old oem 35 or 46 amp and still 20 amps charging at idle. I cleaned all connections and looked for obvious issues and high resistance among any wire runs, but I have;
14.55V at alternator
13.94V at ammeter
13.82V at sensing wire (blue VR wire)
13.55V at battery
Obviously have an issue here somewhere, but its odd that it started with the alternator apparently going bad. Tried another battery, and bypassing the ammeter too, same deal.
Considering the load. That's not terrible.
To answer the first question.
There is an acceptable voltage drop spec but it is tied to the specific tests. It's in some of the master technichian's booklets, and IIRC its in the shop manuals, but I won't swear to it.
Next. I'm going to strongly recommend charging the battery on a battery charger. If its a manually adjusted charger, set it for 5 amps or even better 2 amps. While the alternator can charger a battery at 20 amps, its hard on all of the equipment including the battery. If you put a voltmeter across the terminals while charging, you'll see for yourself how the charging voltage relates to charging rate.
Now lets diagram what you measured and it should make some more sense.
The diagram will assume that ground has no resistance.
We can estimate the alternator's rotor and the ignition use
about 6 amps. So there's about 26 amps flowing out of the alternator to the main splice.
Between the alternator output and the ammeter, there was 0.7 volt dropped.
(We'll assume the welded main splice junction is perfect)
From the ammeter to the battery the voltage drops is 0.3 Volts when 20 amps is flowing through that line. Again can claculate the Resistance in ohms, but that not terrible for 20amps through several connections, including a push on type, and a 16 gage fusible link.
From the main splice to the VR is a 0.1 Volt drop, with a guestimated 6 amps flowing through most of the line.
The biggest drop was in the alternator output line (R6 in the FSM) .
If you want to really know which line had the most resistance, assuming the there grounds are perfect, calculate the resistance using the relationship change in V = I x R. Solve for R.
