68F250 wrote:Hmm, that is strange. The field is going to the starter solenoid? It should be going to the voltage regulator. The ammeter is measuring field current? Gotta think about that.
Actually, it's going to both....one of the three wires coming from the splice at the end of the shunt goes to the voltage regulator.
OK, I think I may be beginning to get a few flickers of understanding here...let me think out loud, and those of you with a bit more upstairs can tell me if I'm headed in the right direction.
When we had the wiring harness out on the floor, hooked up to a battery and a full-instrumention panel, we measured the ammeter leads at the gauge, and both read the exact same voltage as the battery, which led me to believe that there wasn't any resistance wires specifically inserted into the circuit. We measured the resistance of the 10 AWG cable which extended from the starter solenoid to the splice, and at the most sensitive setting on the ohmmeter we read .10Ω resistance, which I figured was negligible and thus immaterial. However, it appears now that this amount might be all the ammeter needs to operate correctly...that is, it really doesn't matter for use with this specific Ford ammeter WHERE the hookup was or the distance apart the two ends of the shunt were located. The power is actually being being 'metered down' by the smaller wire size of the leads going to and coming from the ammeter.
The alternator-to-solenoid wire was 10AWG....if someone were to simply replace the two smaller ammeter leads with 10AWG cables, for example, it would read full voltage and more than likely fry the ammeter.
So why didn't the factory engineers simply hook the shunt between the alternator and starter solenoid? From talking with Earl, he believes it was simply because the engineers wanted fewer connections at the alternator. Having them spliced into the cable and wrapped up would mean it would stay much cleaner and thus the gauge would remain more accurate, since obviously dirty connections would affect the gauge reading....and splicing it into the alternator-to-solenoid cable served their purposes just fine, and it was convenient.