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IH 140 coil keeps burning out

N

NawlensGator

Member
I'm on my 3rd coil and not sure what is going on. Tractor just stops after an hour or so, won't start, and the coil is super hot Let sit for 15 min or so and it will crank and run for a while and stop again. Put new coil on and it will run for a couple hours and then will repeat. With new spark plugs it ran for a couple hours then stopped again, wouldn't start, coil too hot to touch, let sit 15 minutes and it cranked and I parked it.

Anybody have any idea what is going on or what to check? Is the alternator putting out too many volts? Changing coils every few hours is getting old. Help!
 
I ASSUME the tractor is 12 Volt?

Are you using OEM coils, or coils from an auto parts store?

If the tractor uses a ballast resistor, use a coil marked "for use with external resistor".

If the tractor does NOT have a ballast resistor, you need a "true" 12 Volt coil designed for such use. Contrary to what many guys believe, they do NOT have a resistor inside them, they are simply wound with more turns of wire.

The other issue COULD be if the tractor has a ballast resistor and it is nor properly connected into the primary ignition circuit.
 

Thanks for the comments and insight. You see I have 2 IH 140's and they are both set up exactly the same. Coils are both 12 volts with no ballast resistor. The other tractor doesn't have this issue. I think the resistance across each coil is 3 ohms. There is something going on with this tractor that is different. Very frustrating.
 
It does not seem the meter you are using is accurate at low Ohms.

One would expect to see a primary resistance of 3 to not more than 4.5 Ohms on a "true" 12 Volt coil. ^ Ohms isn't "normal".

Do you have a Ammeter capable of reading in the 3 to 5 Amp range accurately? If so, check the primary AMPS (engine not running, ign "ON", points closed), on the two machines and compare them, as well as the battery charging voltages.

You could also swap the "good" coil to the other tractor and see if it gets warmer than on the tractor it"s on now.
 

Thanks for the help Bob. I checked the alternator output on both tractors while running. The tractor without issue was putting out 14.5 volts while the tractor with coil problems was putting out 17.5 volts. Is this enough voltage to cause coil problems?

I guess my volt meter isn't too accurate at low ohms. It's helpful to compare the two systems only. The voltage readings seem to be OK.
 
If your Voltmeter is accurate, 17.5 is TOO high.

14.5 is about what you would expect.

Has the offending alternator ever been updated or is it still a mechanical, external regulator?
 
Time to repair/replace the regulating part of the charging system.
Are you sure the battery cables are making a good connection? The wire from the alternator/generator may have a poor connection.
 

The alternator is the standard 10SI with internal regulator. I just exchanged it for a remanufactured one ($50) at Riley's. Cheap Chinese junk. I'll install it this evening when it cools a little. If it fixes my coil problems it's money well spent. Hope the higher voltage didn't screw up the electronic ignition module.

Thanks for the help. People like you are what makes this site awesome for people like me.
 
I would bet money that's your problem. If you have a voltage regulator it's probably the culprit. If you have an internal regulator you need to pull the alternator and have it checked. Hal
PS: That's too much voltage for your battery.
 

Update. I installed the new (remanufactured) alternator and it was putting 14.5 V. I mowed yesterday for about an hour and had no issues with the coil. So it appears the coils were burning up because a faulty alternator was putting out 17.5 V. I hope this fixes the problem long term. Maybe the coil on it now has already been damaged by the bad alternator and will burn out sooner than later but that's expected.
 
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