Farmall 400 electrical problem

The 400 wouldn't start this afternoon. I checked the plugs and no spark. I took my tester and started at the distributer, no light. I moved to the resistor, power going in and nothing coming out. Then I touched the resistor and it was too hot to touch. Did the resistor just decide to die or did something happen that killed it?? I think I have another resistor somewhere but can't find it, so I'll have to buy another one in order to find the one I have. The resistor gets power from the solenoid on the starter, can that have anything to do with the problem??

bypass the resistor to see if it starts. it should be bypassing when cranking anyhow. they do not last forever.

The resistor does get hot it is a mini toaster by design. But there should (most often) be no measurable power at the distributor with the key on, not running. This is because the distributor/points and condenser are a ground to the coil. (5% of the time a 4 cylinder 4 stroke engine stops, it stops with the pistons about 1/2 the way up or down. (due to compression rebound) this leaves the points closed, grounding the coil. When running the coil is off 50% of the time and on 50%. This interrupted operation causes the spark in the coil secondary circuit. A 400 gas tractor would be 6 volt originally. If it is now 12volt it has been changed. A resistor before the coil allows the original coil to be used. If there is a wire from the starter relay (2 big terminals and 2 small terminals) that would also be add on to the original, but not wrong. The wire to the Relay should connect to a small terminal with an I next to it. The end of that wire chould go the coil side of the resistor, not the key side. It is an ignition bypass, and a good idea.
If the key is switched on for 5 minutes, and the points are closed that resistor will be smoking hot, don't do that. One minute at the most.
If the key is on, and the resistor has power at the key (input) side, and no power at the output side (points closed) the resistor has failed. Maybe from keeping it on too long not running) If there is voltage there with the key on, it should be about 40 to 60% of battery voltage (points closed) Jim

It was converted to an alternator when I got it years ago and is 12 volts. I had just tried to start it and the key had been on for a few minutes before I put the tester on it. I didn't try turning it over while testing.

Pull the distributor cap and make sure the points open and close as the engine spins over. I test light should also flash on and off if the points are working and you don't have a short in the system

Run a wire from the battery to the coil and see if it runs then if you take it away resistor is shot or if it starts with the stater running and stops when starter is stopped then resistor. If not starting when cranking then might be points since switch was on for a time.

They can go bad and do what you are describing with no power coming out. I've had it happen on my H and M and always when you want the tractor and always as far away from the shop as possible. LOL I always keep an extra one around. I think a better deal is to get a 12 volt coil that doesn't need the resistor if you don't mind removing a probably perfectly good 6 volt coil.

To find the cause of no spark simply and easy using no more then your eyes and maybe a 12 volt test light, work through my Troubleshooting Procedure. YES an Ignition Ballast resistor runs hot especially if the ignition is on engine not running. Most common cause IS THE POINTS

http://www.ytmag.com/cgi-bin/viewit.cgi?bd=farmall&th=5745

NOTE you state The resistor gets power from the solenoid on the starter, can that have anything to do with the problem??

1) An Ignition Ballast Resistor (if so equipped, around 1.5 to 2 or so ohms resistance) gets its INPUT power from the Ignition Switch, and its OUTPUT wires to the ignition coil input and such uses a 6 volt coil on a 12 volt tractor so the ballast drops battery voltage down to 6 for a 6 volt coil.

2) If a 12 volt tractor uses a 6 volt coil and ballast PLUS A START BALLAST BY PASS CIRCUIT that feeds unballasted voltage to coil (ballast output) ONLY when the starter is cranking but otherwise the coil gets the reduced ballast voltage from the ballast output to coil.

Test the ballast and work my Troubleshooting Procedure An ignition ballast would read 1.5 to around 2 ohms through it WHAT DOES YOURS READ ?? If its an open circuit power cant get to the coil

If a 3 wire alternator is used with a resistor (instead of diode) to prevent run on after switch is off THATS NOT THE SAME AS AN IGNITION BALLAST What is your ballast used for, is it an Ignition Ballast (between ign switch and coil) or one used with the alternator (between alternator pigtail and coil) ???

John T
John Ts Ignition Troubleshooting

Bottom line is that if resistor is getting hot , there is ~ 100% chance that it is still good and the current flowing thru it is making heat. Look elsewhere as advised.