12V alt with magneto wiring diagram

I need to rewire my H's electrical system. With a lot of help from Janicholson and others I rebuilt the mag last summer and it is working great. My battery is only used to start the engine and run the lights, so I have been doing without it a lot of the time lately. Is there a diagram out there that covers the three wire alt without battery ignition? I asked at the auto parts store for a switch I had heard described on this forum that was closed by oil pressure to connect the alt to the battery but even from the older fellow I got a blank look and no switch. He said he had never heard of such a thing. Does anyone know what that thing is called, or if they in fact exist? I could have imagined them, I guess. Thank you very much for any advice.
Zach

There is in fact a oil pressure type switch you can buy. The 1971 Chev Vegas had them and if you lost oil pressure the engine would shut down and that switch of one like it will work. From there it is very simple to wire it up. The #1 wire from the alternator goes to the oil pressure switch and the other side of that switch to the battery. Oil pressure up then alternator charging no pressure switch is off and not exciting the alternator

(quoted from post at 13:19:32 03/10/11) I need to rewire my H's electrical system. With a lot of help from Janicholson and others I rebuilt the mag last summer and it is working great. My battery is only used to start the engine and run the lights, so I have been doing without it a lot of the time lately. Is there a diagram out there that covers the three wire alt without battery ignition? I asked at the auto parts store for a switch I had heard described on this forum that was closed by oil pressure to connect the alt to the battery but even from the older fellow I got a blank look and no switch. He said he had never heard of such a thing. Does anyone know what that thing is called, or if they in fact exist? I could have imagined them, I guess. Thank you very much for any advice.
Zach

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Zach, I believe the diagram you need is in BobMs diagrams.

I did a google search for it and found a page with several diagrams.
There was more than one diagram for mag/generator combinations
and one for an alternator with a distributor, but I did not see one
for a magneto and an alternator. I will go and look again.
Zach

(quoted from post at 14:59:11 03/10/11) I did a google search for it and found a page with several diagrams.
There was more than one diagram for mag/generator combinations
and one for an alternator with a distributor, but I did not see one
for a magneto and an alternator. I will go and look again.
Zach

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You are over-thinking. A magneto is totally independent of ANY charging system.

I have the same switch in/under the dask of my Moline G-VI but I don't remember what it operates. I think it was the amp gauge.
Someone should have them. I agree with Old, check the Chev Vega.

I used an oil pressure switch with two terminals to turn on the exciting wire to the alt. I have the box over at my shop and I will have to check on the number tomorrow. I tee the switch into the oil pressure line under the hood so it does not show.

I made this a while back, but it is what you need. Bob M just has not put it with the other diagrams yet. Jim

Your think way to hard on this. It is an easy thing to wire up and you do not touch any of the wires for the mag. You simply wire in an oil pressure switch to turn on the excite circuit of the alternator and then you wire the #2 to the big post and the big post has a 10 gauge wire going to the + side of the battery.

Thank you very much, that is just what I needed.
Zach

Rich, Brings back memories as my daughter's first car back in late 1970's was a very nice 1976 Spirit of American model Vega. She used it for several years and was of little or no trouble for the years it was part of the family. She taught skiing in the winter near Seattle and her skis fit right in the car between the seats with the backseat folded down and still had room for a friend up front. In fact, the only problem I ever recall with the car was a front wheel bearing went bad. She loved that pretty little car and hated to see it go. It had been a low milage and garage kept car before we found it. I had teased her for a couple of years that I was going to get her a AMC Pacer as she thought those were the ugliest car ever made and she would have walked everywhere before being seen in one. Hope all is well, Hal.

Ya those Vegas where not to bad a car as for the body but the engine after about 80,000 or so where wore out. My dad got the one I/he had in 1971 and payed $2195 for it. Had a 3 speed in it and was geared pretty high but did handle pretty good. When I finally traded it off I was running a qt. of 85W90 to every 3rd qt of 50W oil and got about 200 mile to the qt of oil, but it did have right at 100K on it

I found the box that I got a two terminal oil pressure switch fir ny 39 H Farmall equipped with a mag.
It's a Standard PS-126 switch. Any good automotive parts store should be able to cross that number to the Brand that they carry.
Some day I'll have to take the hood off and shot some pictures of the alternator and oil pressure switch.
Charlie