Farmall H 12v Conversion

[ratnester]

Trying to get everything ordered to do a 12V conversion on my H (with a mag). I am going with the Hitachi 14231 alternator. I found the diagram online and have everything but an oil pressure switch. I assume you can get these at Napa? If so, does anyone have a part number? Will I need some sort of T fitting also? Anyone know what part number for that is best too? Thanks in advanced for the help.

 

[wore out]

I've used a number of Standard Ignition PS-126 pressure switches for that purpose, 1/8'' male pipe thread, two terminals, close at 2-7 psi.

NAPA can cross that to what they sell.

Use a 5 Amp fuse ahead of it ''just in case''.

Try to mount it so the connector area isn't pointing ''up'' at rain rain or moisture, also they make a two terminal connector that's sort of a rubber ''boot'' to protect that area.

 

[gene bender]

just use a diode you dont need the pressure sw. Just look up BOB Ms wiring pics simple and easy to do

 

[charlieu]

(quoted from post at 15:43:52 05/03/23) Trying to get everything ordered to do a 12V conversion on my H (with a mag). I am going with the Hitachi 14231 alternator. I found the diagram online and have everything but an oil pressure switch. I assume you can get these at Napa? If so, does anyone have a part number? Will I need some sort of T fitting also? Anyone know what part number for that is best too? Thanks in advanced for the help.

Here are a few pictures of what I used to do with the oil pressure switch. Then one day I found a little mini Denso alternator that is a one wire self exciting unit and it works great on the magneto tractors.

 

[Bob M]

Gene - With a 3 wire Denso (or Delco) alternator a diode will not excite the alternator at start. Rather the diode is required on a battery ignition systm to prevent current from back from the alternator to the coil cauing the engine to continue running after the switch is turned off).

So you need 12 volt signal to turn the alternator on at startup. A normally open oil pressure switch will accomplish this.

Alternatively you can replace the OEM single pole ignition switch with a DPDT switch. Wire one pole to energize the alternator when the switch is in run; the other to ground the magneto when at stop.

Or simply use a single wire alternator - though 1-wire alternators have issues draining the battery if left unstarted for long periods.

 

[BunkumBen]

The NAPA P/N for the Oil Pressure Switch I use on 12v conversions is OP6624. I remove the middle oil pressure plug (there are three, use a allen wrench to remove it) in the crankcase (below the Magneto or Distributor) and screw the pressure switch in there. Good luck with your conversion.

 

[ratnester]

Thanks everyone. I wanted to use a one wire to start with but I didn't think there were any available that would fit under the hood. Everything I find online says to use the Hitachi 14231.

Charlie, What is the model of the mini Denso alternator you recommend?

Since it's a mag tractor would I need to worry about it draining the battery over time? Anything I can do to negate besides removing a battery cable each time?

 

[used red MN]

Gene, to avoid confusing the poster you cannot use just a diode on a tractor with a magneto with switch that just grounds the magneto to kill the ignition and has no connection to battery power. The diode is used on machines with a battery powered ignition. In that configuration it feeds the excite circuit in the alternator to initiate charge. The excite circuit is also powered internally when the alternator is charging so that is where the diode comes in to play. When the ignition switch is turned off it does not let the powered excite circuit power the ignition and not let the engine stop. Since you open the contacts in the switch when you shut off the tractor ignition power is no longer able to feed the excite circuit though the diode so the battery is not drawing down as the tractor is setting. If the excite wire is connected directly to a live battery circuit through a diode with its cathode towards the alternator so it feeds the excite circuit when the engine stops the excite circuit will continue to draw current. This is why the poster is adding the the oil pressure switch. When the engine stops the pressure drops and opens the contacts mimicking the ignition switch on a unit with a battery powered ignition. So then there is no power to the excite circuit to cause a battery draw. In the reverse when the oil pressure comes up when the engine starts it feeds the excite circuit and the alternator begins charging.

 

[charlieu]

(quoted from post at 03:34:30 05/04/23) Thanks everyone. I wanted to use a one wire to start with but I didn't think there were any available that would fit under the hood. Everything I find online says to use the Hitachi 14231.

Charlie, What is the model of the mini Denso alternator you recommend?

Since it's a mag tractor would I need to worry about it draining the battery over time? Anything I can do to negate besides removing a battery cable each time?

With the Mini Denso alternator I have not had any problems with battery going dead over winter. Give me a call at 507-438-8172 and I can tell you more about the kit that I have put together for these tractors,