Re: JD 50 Quits

Posted by John T on November 23, 2005 at 20:14:14 from (66.244.90.98):

In Reply to: JD 50 Quits posted by RAHJDH on November 23, 2005 at 17:24:28:

RAH, I agree with Fudd, if theres spark ONLY while the starter is engaged, but it stops firing otherwise and its a battery powered igniton instead of a Magneto, it could be one of the following:

1) The Igniiton Ballast is bad/open if it has one, or

2) The Ignition Switch is bad and not providing voltage out its IGN terminal when turned to ON (use a test lamp to check that), or theres no voltage getting to the switches BAT voltage input terminal (if thats so the lights wont work either), or

3) Theres an open wire from the ignition switches IGN output terminal down to the Ballast Resistor (if it has one) or to the coils high input (NOT to distributor) terminal.

To test it, place a voltmeter or test lamp on the coils high input (NOT to distributor) terminal and turn on the ignition and there should be voltage there to light the test lamp when the Ignition is switched ON !!!!!!!! If not, the ballast is bad/open (if it has one) or the switch is bad (use the test lamp to verify voltage out its IGN terminal when ON) or theres an open wire. If theres no voltage there when ON she cant run. IFFFFFFFFFFFFF the light glows and voltage appears ONLY WHILE THE STARTERS ENGAGED that shows the ballast by pass circuit is good n working and explains how it runs ONLY so long as shes being cranked.

If it has a Ballast Resistor its usually like a 1/2 x 1/2 x 3 inch or so white ceramic 2 terminal block, so see if it has continuity or is bad/open. It should read around 1.5 to 1.85 ohms between its terminals if its good. Its wired in series between the Ignition switches IGN output terminal and the coils input.

If it has no ballast but still runs ONLY when cranking, the switch is bad or the wiring from the switch to coil must be bad but theres still an active working ballast by pass circuit functioning.

If its a 12 volt tractor using a Ballast and a 6 volt coil, how they worked was the ballast dropped 6 volts leaving 6 on a 6 volt coil, but while cranking the ballast was by passed from a wire off the starter switch thats HOT ONLY WHILE CRANKING that wired to the coils input (or low side of ballast, same point electrically) to pump more amps through the coil for a hotter starting spark, especially helpful in winter.

John T, retired electrical engineer

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