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Ignition Coil Failure


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#1 breimer OFFLINE  

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Posted July 23, 2014 - 08:58 PM

1973 case 224. Frequently blowing ignition coils. Which is the only time I run it wide open throttle and give it some load. Twice now a coil has lasted only a couple of hours and then it dies. I check it out and the coil is open circuit. The question is why. Could it be that it's because on this unit the coil mounts horizontally instead of upright? The oil inside the coil is for cooling right? Maybe horizontally it doesn't cool as well? I don't know if this makes any sense but on all my other GT's the coil is upright and none of them has coil failures. Any body else have this kind of experience? I would love some input from others on this. Thanks.

#2 breimer OFFLINE  

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Posted July 23, 2014 - 08:59 PM

Whoops. Only time I run it full throttle is when I now grass with it is what I meant to say.

#3 propane1 ONLINE  

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Posted July 23, 2014 - 09:07 PM

I have one on my LGT 165 Ford mounted sideways and some other tractors with them up and down and have never replaced the coil. Is it wired backwards or is it charging to much. Just some ideas to look at, Noel

#4 DougT ONLINE  

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Posted July 23, 2014 - 09:39 PM

I'd look at an overcharging issue like Neil sugested. The other thought would be that you are using the wrong coil. Some coils have an internal resistor and some don't but they look alike. Check the voltage at the positive post of your coil. If it is the same as battery voltage then you need a coil with an internal resistor. Otherwise, you need to put a resistor in the wire going to the coil something like the old balast resistor on a Chrysler product from the 80's-90's.


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#5 breimer OFFLINE  

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Posted July 23, 2014 - 09:39 PM

The previous owner apparently had coil problems with it as well. When I got the tractor it had the wrong coil on it. (One without an internal resistor) the last 2 coils have been Kohler coils bought at a Deere dealership. It says Kohler right on the box it comes in. I have already changed the regulator as well.

#6 Rock farmer ONLINE  

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Posted July 23, 2014 - 09:45 PM

I would discount the whole mounting position idea.
I think you may be getting bad coils out of the box.
Maybe Chinese made from the same store?
Or, your getting too much voltage to the coil, and that's causing the problem.
Can you use a known good coil from something else?
You might be better off with an old coil that you know is good.
Or buy a better coil from a different maker.

Joe

#7 JDBrian OFFLINE  

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Posted July 24, 2014 - 07:27 AM

Too much current through the coil may be the culprit. If you have replaced the regulator you should not have a high voltage condition. However, you should check the connections in the charging circuit. A bad connection from the regulator to the - side of the battery will prevent the regulator from working properly.



#8 breimer OFFLINE  

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Posted July 24, 2014 - 09:24 PM

Ok I've picked up a new coil today, fabricated a nice sturdy bracket and installed it in the upright position. I realize that most of you probably don't think it's mounting position was the problem. One guy I talked to felt that it was important to have it upright. And I have a crazy hunch that maybe it will make a difference. I started the tractor and checked my charging voltage. It's fairly steady at 12.9 -13 volts. Checked the ground points, all seems good. I don't know what else to check. One guy suggested putting a resistor in the + coil wire. Shouldn't be nessesary with an internal resistor coil. Do ya think I should put one in anyway?

#9 MH81 ONLINE  

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Posted July 25, 2014 - 06:38 AM

You might also check for AC voltage. Shouldn't be there, but it sounds like you've check most everything else.
With an internal resistor, I don't think you should need a second one if everything else is right. Where did you get the new coil, same place?

#10 breimer OFFLINE  

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Posted July 26, 2014 - 07:36 AM

Yeah I got the coil from the Deere dealership where I work . Again it has a john deere part number stuck over top of a Kohler number in a Kohler box. I'm assuming it's an oem Kohler coil. What's a good way to check for a/c voltage?

#11 JDBrian OFFLINE  

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Posted July 26, 2014 - 08:02 AM

Yeah I got the coil from the Deere dealership where I work . Again it has a john deere part number stuck over top of a Kohler number in a Kohler box. I'm assuming it's an oem Kohler coil. What's a good way to check for a/c voltage?

If your battery is good you won't see much AC voltage on the top of the coil. Just put your meter on AC and proceed as if measuring a DC voltage. The alternator charging current is rectified AC which is filtered by the battery. When the battery is charging you should only see a small AC voltage, which represents the peaks of the AC current. The lower the impedance of your battery the less AC you will see. On the lower side of the coil, going to the points you will always see AC voltage when the engine is running. This is normal. The points are switching the coil current on and off. That is what generates the High voltage at the spark plug wire. 

 

   This must be a frustrating and expense problem for you. A few other things come to mind. Heat and vibration may be impacting the coils. If your engine is vibrating a lot due to loose or worn motor mounts or if it is running hot, these 2 things could impact coil life. If for some reason the power is not being disconnected from the coil when the tractor is turned off and the points are closed this will put a continuous DC current through your coil and over heat it, perhaps even burning it out if your battery lasts long enough. This may be worth checking. You should have 0 volts on the top of the coil when the ignition is off. 


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#12 breimer OFFLINE  

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Posted July 26, 2014 - 08:00 PM

Thanks all for your helpful replies.

#13 breimer OFFLINE  

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Posted August 27, 2014 - 10:21 PM

Ok it's been a month. Haven't blown the new coil yet, however I noticed after mowing my lawn today that the coil was very hot. Too hot to touch really. This may be a hint. Don't know why it's so hot. Charging voltage is less than 14. Other parts right beside it were not that hot. So I doubt it's the under hood temp getting that high.
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#14 Alc OFFLINE  

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Posted August 28, 2014 - 05:37 AM

Glad to hear you haven't had a coil go bad since last month . I forgot about this thread , thanks for the update .  I wonder what different causes would make a coil run too hot or maybe they all run that hot ?  How hot is too hot lol ?



#15 Huey OFFLINE  

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Posted August 28, 2014 - 06:41 PM

   Try making an aluminum fin heat-sink and clamping it to the coil. 






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