Soundguy
Old Timer
- Joined
- Mar 11, 2002
- Messages
- 51,575
- Location
- Central florida
- Tractor
- RK 55HC,ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC
I took no offense.. I just see someone spouting off bad electrical theory...
See.. you just changed your story now..
First you stated that running a coil reverse polarity ruined it.
Now you state that you bought a tractor with a coil that had been hot, and changed the coil and the problems was solved.
A hot coil is indicative of internal shorts.. usually cascade shorts which in turn cause more heat, and more shorts, and more current flow, causing more heat.. etc.
This can be caused by over -voltage.. like running 12v on a 6v coil, or it can be caused by lack of a ballast resistor on a 6v coil that needs one, less likely, it can be caused by jumping from a 12v source.. however this usually only happens on a marginl coil.. Another big reason for the cascade shorts and the hot coils are simple thermal breakdown of the insultive tar potting material... most of these coils are vintage and ar not oil filled... outright age and heat and vibration can damage the primary or secondary winding.
IMHO.. you had a coil that was thermally damaged and magically the machine ran better when you repalced the damaged coil.. that's what I see from a diagnostic engineers point of view, based on the info you have provided.
In actuality, if you want to get real technical about it.. a coil running in reverse polarity actually has more resistance inline with the secondary.. and thus, due to ohms law, there will be less circuit current ( and a voltage drop ).. so the coil should actually experience less current /heat based fatigue, thean one running correct polarity orientation that has less series resistance in the secondary.
You can use ohms law to verify this.. E=IR R=E/I. A secondary winding of 4kohms compaired to a secondary winding of 4kohms, plus 1.5 ohms. the one with the larger ohm value will technically have less series current.... as that works out.. the coil that is 'backwards' has the extra series resistance.. thus the big resistance plus the small resistance .
Bottom line.. you had a bad coil.. and it caused problems.. it wasn't a polarity problem.
Please don't -you- take offense when I call somebody out on a bit of bad electrical theory.
If you were a plumber and you heard someone giving dubious advice on plumbing.. you'd feel the same way.
soundguy
See.. you just changed your story now..
First you stated that running a coil reverse polarity ruined it.
Now you state that you bought a tractor with a coil that had been hot, and changed the coil and the problems was solved.
A hot coil is indicative of internal shorts.. usually cascade shorts which in turn cause more heat, and more shorts, and more current flow, causing more heat.. etc.
This can be caused by over -voltage.. like running 12v on a 6v coil, or it can be caused by lack of a ballast resistor on a 6v coil that needs one, less likely, it can be caused by jumping from a 12v source.. however this usually only happens on a marginl coil.. Another big reason for the cascade shorts and the hot coils are simple thermal breakdown of the insultive tar potting material... most of these coils are vintage and ar not oil filled... outright age and heat and vibration can damage the primary or secondary winding.
IMHO.. you had a coil that was thermally damaged and magically the machine ran better when you repalced the damaged coil.. that's what I see from a diagnostic engineers point of view, based on the info you have provided.
In actuality, if you want to get real technical about it.. a coil running in reverse polarity actually has more resistance inline with the secondary.. and thus, due to ohms law, there will be less circuit current ( and a voltage drop ).. so the coil should actually experience less current /heat based fatigue, thean one running correct polarity orientation that has less series resistance in the secondary.
You can use ohms law to verify this.. E=IR R=E/I. A secondary winding of 4kohms compaired to a secondary winding of 4kohms, plus 1.5 ohms. the one with the larger ohm value will technically have less series current.... as that works out.. the coil that is 'backwards' has the extra series resistance.. thus the big resistance plus the small resistance .
Bottom line.. you had a bad coil.. and it caused problems.. it wasn't a polarity problem.
Please don't -you- take offense when I call somebody out on a bit of bad electrical theory.
If you were a plumber and you heard someone giving dubious advice on plumbing.. you'd feel the same way.
soundguy
