140 Farmall alternator


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140 Farmall alternator

John Beck I have a 1965 140Farmall that has be coverted to 12 volt and a alternator added with a resistor . The problem is the battery will not show a charge on the gauage only a discharge. Had alternator checked at local auto store,was showing charge and OK. any ideas? Thanks
Hugh MacKay John: That is what gauge says, however is it charging? Is this alternator hook up 1 wire, 2 wire or 3? Is there a system in place to excite the alternator and start it charging?

I have a late 63 140, I converted to 12 volt alternator. I used a 12 volt coil rather than resistor. I have 3 wire system with a push button wired in for exciting the alternator. I would have to look, before telling you how I did that as it's been 4 years. After the tractor starts I just push the button to excite the alternator. My tractor only shows charge for 30 seconds after starting. I believe this is because the alternator keeps battery so well charged this is all it takes to maintain it. It has been working well for 4 years.

My SA and 130 have been working well with this setup since 1992. I fooled with those resistors a few years back then, decided it was cheaper to buy 12 volt coils. I also spent a period trying to make low ohm lamps and diodes excite the alternator, and decided there had to be a better way. I went with the push button about 1994, it's been trouble free since.

MGS If I recall correctly, the ammeter on those older tractors is directional, it actually measures current flow. So if you switched from pos ground to neg ground and didn't switch the wires on the ammeter, a charge would look like a discharge.

You could check this by using a voltmeter to see what you have when the engine is running. You should see 13 or 14 volts.

fred you can hot wire the alternator excition circuit to the ignition switch if you just add a forward biased diode to the set up. this allows current to flow to the excitation terminal but prevents back feed. i used a 1978 chevette alternator on my 140 and 240 models. excitation tab is supplied through a 1N4000 series diode and has worked well for many years now. if you don't use the diode the tractor will not shut down when the ignition is switched off. these diodes can be had from any electronics surplus dealer for 5 cents or less.

as to the guage check the wiring. its not uncommon for people to remove wires and get them mixed up. just switch them post for post. if you turn on a load when the engine is NOT running and a charge current is indicated on the amp guage then for sure the wires are mixed up.

as for using 6 volt stuff on 12 volt systems there are several, options:

fixed loads use a properly sized dropping resistor and be careful where you mount it. they can get hot.

used 4 silicone power diodes in series. this works well for lights and other variable loads. doides must have ample heat sinking.

for sensitive things like radios etc. used a dedicated regulator with a booster transistor if needed to satisfy current needs. i have used the 309 series regulator (TO-3 and tab) with a diode added to the ground leg to boost the nominal five volts of the 309 to about 6.5. again proper heat sinking is required.

i have used all these options on numerous IH trucks and tractors.



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