Been having problems with the battery going down on my 640 that I bought about a month ago. Previous owner done a 12 volt conversion. When I started tracking single wire from alternator back, I found that it wasn't attached to anything just loose. I have pulled up different wiring diagrams and can't determine where it goes. One shows it going to a two point junction ( or what ever it is called) and other shows it going to post on starter solenoid where positive from battery connects. Can anyone please tell me?
jaotguy
Veteran Member
what type of alternator is it ? GM , ???? pics please .....
if its a 1 wire alternator it should have the big wire from the alt go to the battery + (or to the + at the starter )
if you have a multi wire alt , there may be several smaller wires to supply initial power to excite it and a reference voltage wire ( or you may be missing an external regulator completely )
if its a 1 wire alternator it should have the big wire from the alt go to the battery + (or to the + at the starter )
if you have a multi wire alt , there may be several smaller wires to supply initial power to excite it and a reference voltage wire ( or you may be missing an external regulator completely )
Alternator was on tractor when I bought it. There is one larger wire coming from a post on back of alternator and two smaller wires coming from what looks like a plug on bottom of alt.. All three are spliced into one leading back toward the battery area.
jaotguy
Veteran Member
sounds like a GM .... probably SI ... pics would be nice to confirm ....
big wire goes from big alt post to the battery ...
the 2 smaller wires are the 12v sense / reference voltage and the exciter circuit ...
if the 2 wires are tied to the battery directly , they are constantly trying to excite the alt ... and will drain the battery ....
more on wiring when you take pics (or verify its GM )
big wire goes from big alt post to the battery ...
the 2 smaller wires are the 12v sense / reference voltage and the exciter circuit ...
if the 2 wires are tied to the battery directly , they are constantly trying to excite the alt ... and will drain the battery ....
more on wiring when you take pics (or verify its GM )
jaotguy
Veteran Member
NO ...
one of the GM wires (12v sense /reference) must be connected to the proper alt connection at least .... otherwise it has no way of knowing what the output voltage is ... with it connected ( through the hot when run , ignition on ) , the unit will self excite when you get up over 2400 RPM .... the exciter circuit ( other wire and usually idiot light ) supplies power to the internal reg to start charging at lower speeds ...
all of this assumes that it is a GM alt ...
one of the GM wires (12v sense /reference) must be connected to the proper alt connection at least .... otherwise it has no way of knowing what the output voltage is ... with it connected ( through the hot when run , ignition on ) , the unit will self excite when you get up over 2400 RPM .... the exciter circuit ( other wire and usually idiot light ) supplies power to the internal reg to start charging at lower speeds ...
all of this assumes that it is a GM alt ...
jaotguy
Veteran Member
a large RED goes from the big BATT post on the alt to one side of your ammeter , out the other side and over to any large POS connection on the battery ( you can skip the ammeter and go directly to the battery , but the gauge will not read )
you need a wire ( any color about 16 gauge ) from the I terminal on the ignition switch to the #2 pin on the alt ...
you can then just put a small light bulb (with a connector and 2 wires ) between the #1 and #2 pins .. the light should come on when you turn
the key to ON .... and go out when the engine starts , if it doesn't , the alt is not putting anything out .
or run a wire from the I on the switch up to a light on the dash somewhere and back to the #1 on the alt ...
the black yellow used to be the wire going from the original alt output to the ammeter gauge ( and RED out the other side, back to the big POS wire on the starter ) It should have been about #8 or #10 wire ... but it looks like you'll have to trace to see if its still connected , or has been bypassed during the original conversion .... ( or leave it bypassed )
one word of caution ... if the smaller pins are not labeled 1 and 2 and have R an F instead , you have an alt that needs an additional external regulator to work
you need a wire ( any color about 16 gauge ) from the I terminal on the ignition switch to the #2 pin on the alt ...
you can then just put a small light bulb (with a connector and 2 wires ) between the #1 and #2 pins .. the light should come on when you turn
the key to ON .... and go out when the engine starts , if it doesn't , the alt is not putting anything out .
or run a wire from the I on the switch up to a light on the dash somewhere and back to the #1 on the alt ...
the black yellow used to be the wire going from the original alt output to the ammeter gauge ( and RED out the other side, back to the big POS wire on the starter ) It should have been about #8 or #10 wire ... but it looks like you'll have to trace to see if its still connected , or has been bypassed during the original conversion .... ( or leave it bypassed )
one word of caution ... if the smaller pins are not labeled 1 and 2 and have R an F instead , you have an alt that needs an additional external regulator to work
8N Ren
Gold Member
This might help a bit, it says Farmall but it's all the same components. Depending on the coil your using you may not need that resistor.
