square back alternator

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ir3333

ir3333

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when using a 2 field sq back alternator on a '69 single fld charging system i believe you ground one field terminal and connect the field wire to the other alternator field terminal.
..is that correct?
..how do you ground one of the alternator terminals?
 
There is a special connector that grounds it from the rebuilders.

I think that you could just use a flat blade terminal and wire to any ground if you can't get the connector.
 
Just install a short piece of wire with a female terminal on it. One end on the field spade, the other end to ground.
 
If you are careful in your selection, you can "select" the proper size metal washer and replace one of the insulator washers with that. Be sure to remove / cut the other blade off if you do, in order that you don't accidently connect a hot wire

I would just ground the existing, that way if you ever convert to the newer regulator, all you need do is add one more wire
 
..so an easy alternative is to just run a wire from one field terminal to the alternator case?
 
O.K.....is there any advantage running a newer squareback 55 amp on a '69 single field charging system other than increased capacity?
 
^^THIS^^ The squareback is a better design, and is known for better output at lower RPM
 
Newer squareback installed and one field wire grounded.
took an ohm reading from the isolated field terminal to ground and got 11.6 ohms (wire not connected)....sound correct?
 
That's a bit high but might be because the brushes are "in a bad spot." In the shop manual, there's a mention to measure rotor amperage draw, and they mention to loosen the belt and turn the rotor.

These draw between 3 "something" and 6 amps, so to draw that amount at 12V you'd expect a lower resistance reading.
 
..my old single field alternator reads about 4 ohms field to ground.
i had this newer square back alternator and thought i'd try it.
how much harm can i do by test running it this way on the car?
 
No harm. Your 11 ohms you read may be dirty brushes. Run it and see if it charges. If it's erratic, or low, you may need to replace the brushes. Or try checking again while rotating the pulley as mentioned. I would expect either reading to be closer to the 4 ohms you mentioned
 
More resistance is safer. Worst-case it will not charge your battery as well, but you can monitor that (if dash ammeter works). To make it go "full field", apply 12 V to the field wire (disconnected from Vreg) and see how many amps output you get.

It is hard to measure 4 ohms accurately. Always, first short the multimeter leads together and subtract that from future readings. Perhaps the armature has more turns of wire. It is the Amps x turns product that determines the magnetic field.
 
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