I have a Motorcraft 1g alternator on the 302 in my '56. I'm wiring the car from scratch, and have not connected any of the lights or dash wiring yet. yesterday I found that when I turn the key to "on" that there is a steady voltage drop, about one hundredth of a volt a second. Doesn't sound like much, but would add up pretty quickly. On a suggestion from a friend, I disconnected the power wire from the alternator. The voltage drop stopped. I have everything wired as per diagrams and advice from people who should know. Alternator - 12v+ from solenoid (where battery cable attaches) to positive post on alternator Ground from engine block to ground post "F" (field) post to "F" connection on regulator "S" (stator) not connected to anything Regulator - "I" connection not used "A" to positive post on alternator through fusible link "S" to switched 12v+ "F" to "F" (field) post on alternator. Is there a problem with the alternator itself? I'm not much of an electrician, so I don't understand how disconnecting the positive post stops a voltage drop that happens with the ignition switch turn on. I'd appreciate any help.
Animal, when I did a alt conversation years ago, I used three of the terminals on the electronic regulator, if I remember correctly. I switched the i terminal and took the s terminal to stater. F to field. That’s been a while. Didn’t have a choke. Bones
That may be normal, an alternator need 12 volt + to it to energize the field coils so that it will make electricity. (I believe this is correct) As long as it is not drawing current when the key is off I would say it's OK.
What you have is probably normal, although you might have a diode 'leaking' slightly. Test for this by checking between the 'BAT' terminal on the alternator and the alternator housing using a meter with the alternator disconnected. It should read open. Two suggestions I would make is one, to connect the ground at the alternator to the regulator base. It's important that there should be as little difference of potential between these as possible, don't depend on the ground path from the engine block to the regulator housing through the body. Second, connect the 'A' terminal from the regulator to the same place you connect the 'bat' terminal from the alternator. This is a 'sense' wire, and under a heavy load will raise the voltage output to compensate for voltage drop in the charge wire from the alternator. Connecting at the alternator will defeat this. You don't need any connections to the 'S' terminal at the alternator, although this can be used to power an electric choke.
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