What could be killing coils?

Help! I've traced my 8N starting problem to a bad coil. The distributor is a front mount with the original 6V system and a good battery. I've replaced the coil with a new one. The tractor started right up and ran well for a few minutes. Then it wouldn't restart. I tested and found the new coil to now be bad. I don't want to buy a new coil to then have it go bad too. What could be causing coils to go bad? I have a new voltage regulator (although I don't know what difference that would make), new properly gapped points, and a new condenser (that I checked and found to be charging and discharging properly).

I've been told that the ballast resistor could be bad. Its only a few years old though, and I figured if the resistor were bad I wouldn't be getting voltage to the coil.

Any tips anyone? Thanks in advance.
 
The number 1 reason for burning up a front coil is leaving the key on.

The number 2 reason is cheap-azz off-shore replacement coils.

The absence of the oem ballast resistor on a front coil will not cause it to burn up in a few minutes of run time.

But, how did you determine the coil is defective?

I?ve always found it best to determine if a part is actually defective before I buy a new one.

About 5 years ago, my neighbor proudly told me about fixing his 8N. Seems like it wouldn?t start, so he replaced the coil. Tractor started, problem solved. I asked him if I could have the old coil. He gave it to me. I put it on one of my 8N?s where it has been ever since.

I do not know why his tractor would not start. I do not know why it did start and ran fine after he put a new coil on it. Sure, I can make a lot of guesses, but we will never know for sure.

But I do know he did not have a bad coil.

Think about this the next time you are inclined to just start replacing parts w/o determining if the part is defective.
75 Tips
 
Thanks Bruce. You're right, it makes no sense to just start replacing parts. I checked the coil by connecting 6V to the input, jumping from the primary to the points, grounding the distributor to the positive on the battery, and checking if there's a spark when the points are closed and I connect a jumper from ground to the secondary. No spark.

I also checked the condenser by loading it up with an ohm meter, then watching it drain when measuring DC volts.

I bought the new coil through YT. Shouldn't this be a good quality coil?
 
Yes, it should be.

Check the resistance between the stud and
the pigtail. Should be around two ohms.
Then check the resistance between the
stud and the pigtail. Should be 8k or so.
75 Tips
 
Hi Back Woods, Bruce gives out great advice. But I noticed something in you post, that you have a new voltage regulator. I've recently gone through two off brand ones and then an Echlin from NAPA on my NAA. The one from NAPA worked for awhile, then quit. The generator tests out just fine at an auto electric shop. Bottom line is that parts made from the land of almost right don't last or don't work from the beginning. In your case, once you get him fired up again, check the voltage at the top of the coil.
 

This helped me immensely - gives you a definite go/no go on your ignition system.

https://www.youtube.com/watch?v=rzpW0R_mh3U

Hope it helps,
 
(quoted from post at 18:56:15 07/14/19) Thanks Bruce. You're right, it makes no sense to just start replacing parts. I checked the coil by connecting 6V to the input, jumping from the primary to the points, grounding the distributor to the positive on the battery, and checking if there's a spark when the points are closed and I connect a jumper from ground to the secondary. No spark.

I also checked the condenser by loading it up with an ohm meter, then watching it drain when measuring DC volts.

I bought the new coil through YT. Shouldn't this be a good quality coil?
... and checking if there's a spark when the points are closed".
HV spark occurs when points OPEN.
 

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