WOW... Lets get this fixed!

I just looked at this page and found a partial answer to my question, which I posted a short while ago. From your photo, I can see I have three options, a resistor, a bulb, or a diode going to the alternator exciter terminal. After seeing what you posted, I think the original plug that came with my Farmall H must have had the diode. It was molded onto the top of the alternator pigtail plug, and embedded in some sort of rubberized material. Because of this I was unable to see what it was. It burned out and I thought I needed a resistor.

In my post, I mentioned that I have been using a bulb on the side of the engine block but I keep breaking it. I did not know what size resistor to buy, and no parts store could help.

Since you mentioned the overheating of a resistor if the IGN is left on, I know I did not have a resistor, since I have left the IGN on far too many times and nothing ever got hot or melted. I bet it was a diode embedded in that rubber goop.

You show a 1N5408 diode. I know electronics, and how to use a Diode, but where I live, we do not have any electronics stores unless I drive 50 miles to the city and go to Radio Shack. So, I need to know the specifications for that diode. Radio Shack usually only rates them by volts and amps, and no actual part number. What do I need as far as volts and amps? Is the part critical, in as much as can I use any diode that is at least whatever amperage I need, and can handle at least 20 volts or so? I am asking because I have lots of old tv chassis with rectifier diodes, which wont cost me a cent or a long trip to the city.

One other thing. I noticed that many of the discussions on here mention that the tractors converted from 6 to 12 volts need a block resistor to the ignition coil (like in the old Chrysler cars). My coil does not have one. However, my coil is a 12V coil from a 12V car (I replaced it when I bought the tractor because the old one was arcing thru a tiny crack). Should I still have one, and why? It almost seems senseless to buy the resistor, mount it, and wire it, when 12V coils are a dime a dozen at most auto junk yards.

By the way
My neighbor has a Farmall 400, and he has that resistor on his. His tractor was also converted to a 12V system. I dont know if he has the 6 or a 12V coil (they all look alike).

Thanks

Horse-George

I use the 1N5408 diodes 'cause they are about BULLETPROOF. They are rated3 Amps @ 1000 PIV., which is WAY overkill for this application, but I don't see any failures with them. They cost so little to buy, for me it's not worth using lesser-rated units.

Some guys use diodes of much lesser ratings, but SEEM to get by with them, as low as 50 PIV. HOWEVER, when the ignition is switched off, and the magnetic fields in the ignition coil and alternator rotor collapse, the diode gets zapped with a pretty good spike of electricity.

Are you in Minnesota? If you need a diode, I'd stuff one in an envelope, and drop it in the mail to you, and you probably have it in one or to days.

email me, if you'd like, bigcoulee@hotmail.com