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I'm getting close to firing up an A318 Poly that I put in my '68 D100. As I'm using a '70 cab, I'm also then using the later wiring harness. The alternator is original equipment to the Poly ['66 vintage] and is a single field. My wiring has what I'm assuming to be
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Re: Alternator Question....
Posted by:
shartwig
(76.229.88.---)
Posts: 222
Posts: 222
Date: August 23, 2009 01:30PM
here's the deal:
one wire alternators use a wiring harness that varies the POSITIVE voltage to the field, the other side of the field is case grounded
the two wire alternators, use a wiring harness that applies the FULL POSITIVE VOLTAGE to one side of the field and varies the resistance to ground through the "box"
Alternators charge the battery by how much current you put through the field, the amount of current needed is determined by the battery voltage.
here is what will happen if you "mix-up" the two, as soon as you put a one wire alt on a two wire harness, the AMP gauge will show full charge and will NEVER stop charging
if you put a two wire alt on one with a one wirh harness you will not have any current flow and show no charge, now here's the deal with this , "you can ground one side of the field" and it will work.
the old systems varried the current flow in the field using 3 resistance coils mounted high on the firewall, if your battery voltage was low, it pulled in the coil with the low resistance and allowing more current flow through the alt field, as your battery charged it would lower the current flow through the alt field by switching resistance coils and eventually when the battery was fully charged it would cut off the current to the alt.
the newer electronic system uses an electronic box, in that box there is a power transistor, you can see it, its the round thing about the size of a quarter. the transistor, does the same job as those three OLD COILS, here is how it works, it is like a single switch, and it charges the battery by varing the current flow through it and since it is in series with the alt field and in a "series curcuit" current is the same. when the battery needs more voltage this transistor allows more current flow thus charging the battery.
a couple things to remember , current and voltage ARE NOT the same thing
ohms law where E is voltage and I is current and R is resistance
E=IR
I=E/R
R=E/I
i have sparked many screwdrives and wrenches, burnt tons of insulation off wires in this quest for knowlege.
one wire alternators use a wiring harness that varies the POSITIVE voltage to the field, the other side of the field is case grounded
the two wire alternators, use a wiring harness that applies the FULL POSITIVE VOLTAGE to one side of the field and varies the resistance to ground through the "box"
Alternators charge the battery by how much current you put through the field, the amount of current needed is determined by the battery voltage.
here is what will happen if you "mix-up" the two, as soon as you put a one wire alt on a two wire harness, the AMP gauge will show full charge and will NEVER stop charging
if you put a two wire alt on one with a one wirh harness you will not have any current flow and show no charge, now here's the deal with this , "you can ground one side of the field" and it will work.
the old systems varried the current flow in the field using 3 resistance coils mounted high on the firewall, if your battery voltage was low, it pulled in the coil with the low resistance and allowing more current flow through the alt field, as your battery charged it would lower the current flow through the alt field by switching resistance coils and eventually when the battery was fully charged it would cut off the current to the alt.
the newer electronic system uses an electronic box, in that box there is a power transistor, you can see it, its the round thing about the size of a quarter. the transistor, does the same job as those three OLD COILS, here is how it works, it is like a single switch, and it charges the battery by varing the current flow through it and since it is in series with the alt field and in a "series curcuit" current is the same. when the battery needs more voltage this transistor allows more current flow thus charging the battery.
a couple things to remember , current and voltage ARE NOT the same thing
ohms law where E is voltage and I is current and R is resistance
E=IR
I=E/R
R=E/I
i have sparked many screwdrives and wrenches, burnt tons of insulation off wires in this quest for knowlege.
