[Farmall] International A died (and I am baffled)

[Stan Bass]

The diode (or a dash lamp) is only required when you use the ignition switch to feed both the coil and the alternator terminal to stop the "engine won't shut off" problem. Have never installed an oil pressure switch but the idea sounds fine. Use a normally open switch that mates with pressure present, and sends 12V to the alternator. This could be used instead of a diode as long as it received it's 12V source from somewhere other than the switched line feeding the coil (like raw 12V off the battery) or it would still have the run-on problem.

My experience with coils has been the original 6V coils are about 1.2-1.5 ohms, the 12V coils are about 3 ohms (I see values ranging about 2.7-3.3 ohms). Not that it applies to this discussion, but FWIW the coils on old Cub Cadets with the single cylinder Kohlers typically measure about 4.5 ohms.

And I agree with Mike, the electronic ignition kits are great!
Stan(VA).


....
> Ivan,  I am not the best at explaining, but here is
> the url of an article of Yesterday's Tractors.  As the
> author noted, some diesel configurations connect the exciter
> wire through a diode the oil-pressure sending unit. 

....
> Larry , could you explain the oil pressure exciter for an
> alternator ? Would 
> it just be a pressure switch to supply power to excite the
> alternator when 
> its running , as opposed to converting it over to one wire
> .   Ivan