Cub Lowboy 154 coil

I've been having trouble with the tractor quiting after about a half hour use and have been suppecting the coil. Well today it was boiling when the engine quit. I needed to get the tractor home to the shop from where it quit, so I found another coil that was too big for the mounting but hung on until I got to the shop.

Now, my question- the coil that I used was from a 1986 Nissan Sentra. When I started the tractor with this coil it started very quickly, almost instantly. I'd like to mount this coil instead of buying another since it just an extra coil laying around and it started so well.
What harm to the ignition system or might result from using this coil. It may not have an internal resistor as there was some type of round capacitor looking thing attached to the original mounting bracket from the car but only had one wire going to the coil.

What do you think?
Thanks,
Loren
 
"What harm to the ignition system or might result from using this coil."

If the coil is too much less resistance then the stock coil, the points will burn up prematurely and the coil may overheat if subjected to more voltage then it was designed for.

The old tractor points system wasnt designed to switch much over 4 amps of coil current and if so points burn up quicker

Instead of pumping 4 amps into to a coil for saturation then interrupting current flow to create the HV spark (like original points ignition) some modern cars pulsed the coil to make it fire and while the wrong coil can still yield a spark, if the points switch too much current they will fail soon.

Id get a correct coil to match the tractors voltage AND DONT FORGET TO MATCH COIL POLARITY TO TRACTOR

John T
 
While I've had the tractor 15yrs, you could be correct in that it may have had the wrong coil from previous owner. No resistor is seen so I assumed it was internal. This is a 1975 Cub Lowboy 154 -12 volt ignition.

Should the correct coil have an internal resistor? Could I just add a resistor inline with the coil I have?
 
That is what I'll most likely do, but was hoping to put this extra coil to use rather than having it set on the shelf.
Thanks,
 
measure the primary resistance. If it is 3-3.5 ohms.. it will be ok.

if it is less, you would then have to buy a resistor.. I'd buy the correct coil before buying a resistor.. IMHO.
 
No modern coil has an internal resistor, its "internally resisted". No resistor is needed. The number Soundguy gave you will work fine, but I suspect the coil form the Nissan will be fine. The part on the bracket was just a device to control radio noise.
 
Thanks guys, the tractor isn't used much so if it only burns the points, I may try the Nissan coil for a while and watch it for heating up.
 
I found info on the round resistor looking thing on the Nissan coil bracket. It is a transistor used to amplify the current from the Electronic Control Unit to the coil to give the coil enough voltage to fire the plugs. It may also pulse the current to the coil.

I'm still going to check the ohms of the coil and if close to 3ohms, I'll try it.

Thanks again-
 

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