400 Ignition System

[pmf]

400 had 12 volt positive battery when I got it 5 years ago. Have had no problems starting at all until last weekend. Went to start after tractor sat over the winter and no start. Checking ignition system had no spark at points then noticed smoke coming from the device between the hot wire and the coil. Device was also too hot to touch. This happened within about 3 minutes of turning switch on.

Any thought on what's happening here? I have 12 volts coming into the device and 6 volts outgoing. Does this mean I have a 6 volt coil? The device was on the tractor when I got it. Not too sharp on electrical ignition.

 

[Charlie M]

When you convert a tractor from 6 to 12 volts you either have to change the coil for 12 volts or add a resistor to bring the 12 volts down to 6 volts. You have a resistor and chances are its gone bad. You can get a new one from an auto parts store or purchase a 12 volt coil and remove the resistor. I have 3 tractors converted to 12 volts and all but one has had the resistor go bad in the past year. Personally I think changing the coil is the better way to go but it costs considerably more than the resistor. In your case changing the resistor will be cheap and quick.

 

[John T]

I agree. It looks like a 12 to 6 voltage dropping ballast resistor which is what is used on a 12 volt tractor that uses a 6 volt coil. They DO run hot and the physical mounting procedure and heat transfer method affects their temperature. You can buy them at about any tractor Big Box store or auto parts stores. With the points closed and ignition on there should indeed be battery voltage on the input and around 6 volts on the output which is what you found, so that sounds like its working okay ??????????? maybe there's a different problem ???? See my link below if needed.

John T
John Ts Ignition Troubleshooting

 

[rvirgil_KS]

"I have 12 volts coming into the device and 6 volts outgoing. Does this mean I have a 6 volt coil?"

Yes, it means you have a 6 volt coil.

Voltage at output of the resistor to coil should be about 6 volts with points closed and near battery voltage with points open. Does this voltage change as you rotate the engine?

Your given readings indicate the points are closed and with switch on current flows through points and coil and resistor will get hot.

If voltage does not change as you rotate the engine, check that your distributor is turning, the points are opening, and that you have .020 gap with points open. Also check that there is no arc deposits on the points that will cause them to keep contact when open and check for possible short in the feed through on side of the distributor

 

[Bob]

(quoted from post at 07:31:11 04/30/18) When you convert a tractor from 6 to 12 volts you either have to change the coil for 12 volts or add a resistor to bring the 12 volts down to 6 volts. You have a resistor and chances are its gone bad. You can get a new one from an auto parts store or purchase a 12 volt coil and remove the resistor. I have 3 tractors converted to 12 volts and all but one has had the resistor go bad in the past year. Personally I think changing the coil is the better way to go but it costs considerably more than the resistor. In your case changing the resistor will be cheap and quick.

Charlie, what makes you tink his resistor is "bad'?

If it's HOT it's doing just what it's supposed to, RESISTING the flow of current by turning it into heat.

It's the CCCOLD ones you have to worry about!

 

[pmf]

Hey thanks for the quick reply's. As always the help is appreciated

 

[Charlie M]

Maybe I'm not reading the description correctly but I saw "too hot to touch" and "smoking" so I'm thinking it was the resistor being described. Since they do go bad I said what I said. Easy way to find out is with a volt meter. I could be wrong. Wife says I'm wrong all the time.