[AT] question on use of resistor on coil

[Ronald L. Cook]

Cecil,
	It has been my experience that there are no 12 volt coils.  They are 6 
volt coils that require resistors.  If they are marked 12V on the coil, 
it has an internal resistor.  Otherwise, an external resistor is 
necessary to cut the running voltage to something less than 12 volts, 
probably in the 4 to 5 volt range to insure longevity of the rest of the 
ignition system.  This is my opinion.  For a fact, the 420 ignition 
system is the same as the 40 ignition system as stated in the 420 
service manual.  6 volt and uses the Delco Remy No. 1115379 coil.  No 
resistors in the ignition system.  Only in the lighting system for "dim 
lights".
	My engines that sit, be them John Deere, Willys, Wisconsin, etc. almost 
always give me starting troubles until I clean the points.  Often I 
clean them by installing new.  Sometimes touching up with a file will 
work.  I have had corrosion in the primary wire and also at the switch 
contacts which set up a resistance that ruined or completely eliminated 
a spark.  Making more cleaning and replacing necessary.  Moisture 
induced problems, I think.  On engines that are used constantly, this 
never seems to be a problem.  You could give me the 420C and I would see 
that it runs more often.<g>

Ron Cook
Salix, IA



Cecil E Monson wrote:
>     I've been trying to get my JD 420 crawler to start after sitting
> all summer. At first I had no spark. With the loader down and the hood
> on the tractor, it is almost impossible to get to the coil and to where
> you can see to work on the distributor. I took the hydraulic connections
> apart yesterday and got the hood off. Substituted a new coil for the old
> one without success. Took the cap and rotor off the distributor and used
> a "point file" I got at Sears to clean up the points. Now I have a sort
> of yellow spark when I lay a spark plug where it is grounded and crank
> the engine over. The yellow spark indicates to me it is a weak spark
> or still bad contacts at the points.
> 
>     The question is - the coil came out of the box with a note saying
> it must be used with a resistor but no resistor is there. I figured that
> being as it is marked 12 volts on the coil and I'm using it on a 6 volt
> system, I should not need a resistor. Is this true or do both 6 volt and
> 12 volt systems use the same coil with a resistor?
> 
>     Another question is that I can feel pitting on the points on one
> side when I run the file over them. Would you just change out the points on
> general principals?  I have already changed out the condenser as I 
> initially
> thought it might be the problem.
> 
>     In case someone wonders about fuel, I smell gas in the exhaust when
> cranking so it is getting gas.
> 
> Cecil