12V coil question

Greetings from the great white north!

I have a 2N, converted to 12V, that I use to blow snow during the winter. When I went to start it last weekend, after sitting all summer, it would turn over, but not fire. Investigation revealed no spark at the plugs. Using my volt-meter, with the ignition on, I'm showing 12V at the top of the front-mount, square coil. When I removed the coil from the top of the dist and, with the ignition on, I'm showing no volts at the bottom pigtail spring. Is the coil dead and need replacing with a new 12V square coil? The points and condenser are fairly new and the tractor was running perfectly when I parked it.

Thank for your help,

Dave

(quoted from post at 09:12:43 10/20/09) Greetings from the great white north!

I have a 2N, converted to 12V, that I use to blow snow during the winter. When I went to start it last weekend, after sitting all summer, it would turn over, but not fire. Investigation revealed no spark at the plugs. Using my volt-meter, with the ignition on, I'm showing 12V at the top of the front-mount, square coil. When I removed the coil from the top of the dist and, with the ignition on, I'm showing no volts at the bottom pigtail spring. Is the coil dead and need replacing with a new 12V square coil? The points and condenser are fairly new and the tractor was running perfectly when I parked it.

Thank for your help,

Dave

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e sure that at the same time you have 12v at top terminal that pig tail is zero as you said. Some connections might have loosened or wire opened as you removed coil from distributor. There is only a coil of wire inside between the top terminal & the pig tail and that amounts to ~2.5 ohms on 12v coil, so if voltage is on one terminal and the other is connected to nothing, then both should measure same voltage.

Thanks for the reply JMOR,

I"ll recheck to confirm that there is no continuity thru the coil.

Dave

(quoted from post at 09:48:38 10/20/09) Thanks for the reply JMOR,

I"ll recheck to confirm that there is no continuity thru the coil.

Dave

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he coil typically sold as "12v" is about 2.5 ohms primary (green in pict) and 6v coils range from 0.5 to about 1.5 ohms.
Red Secondary about 6,000 ohms

Sorry, I"m a little electronically-challenged, with respect to coils. Looking at your picture, is that depicting a 12V system with a 6V coil? I"m reading 12V at the top the coil. Is it possible my resistor has failed, causing the 6V coil to be burnt out? I"d hate to install a new coil, only to fry that one too.

You gotta love these forums for this kind of help!

Thanks,
Dave

Dave.......iff'n yer "infamous ballast resistor" failed, (its like a litebulb) you would gitt NO VOLTS at the top of yer 1-terminal squarecan ignition coil. Its the LAW, Kirchhoff's Law.

While many squarecan coils fail because of overheating and melting the insulative tars and shorting out some of the coil windings, very seldom do the winding "open" and NO VOLTS at the bottom of the springy-thingy. Its the LAW, Kirchhoff's Law. (that guy is everywhere in electronics circuits)

And NO, that is NOT a 6-volt coil drawing, the voltages represented are typical 12-volt squarecan coil with the "infamous ballast resistor". .......Dell, yer self-appointed sparkie-meister

(quoted from post at 11:00:21 10/20/09) Dave.......iff'n yer "infamous ballast resistor" failed, (its like a litebulb) you would gitt NO VOLTS at the top of yer 1-terminal squarecan ignition coil. Its the LAW, Kirchhoff's Law.

While many squarecan coils fail because of overheating and melting the insulative tars and shorting out some of the coil windings, very seldom do the winding "open" and NO VOLTS at the bottom of the springy-thingy. Its the LAW, Kirchhoff's Law. (that guy is everywhere in electronics circuits)

And NO, that is NOT a 6-volt coil drawing, the voltages represented are typical 12-volt squarecan coil with the "infamous ballast resistor". .......Dell, yer self-appointed sparkie-meister

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Thanks, Dell.

Thanks for the info, but I"m a little confused by the diagram. I"m reading 12V at the top of the coil, not 7V. Is that normal? If not, what is the probable cause(s)?

If I need to replace the coil, I"m wondering if this would be a good opportunity to upgrade to an electronic ignition and get rid of the square coil, points and condenser?

Dave

(quoted from post at 11:38:16 10/20/09) Thanks for the info, but I"m a little confused by the diagram. I"m reading 12V at the top of the coil, not 7V. Is that normal? If not, what is the probable cause(s)?

If I need to replace the coil, I"m wondering if this would be a good opportunity to upgrade to an electronic ignition and get rid of the square coil, points and condenser?

Dave

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hen the points are open, there is no current flow, hence no voltage drop, so you see the full battery voltage.

Don't further complicate matters until you make it run by adding more unknowns to the equation.

After you fix current problem(s), only then should you decide if you want EI OR not.

Thanks JMOR, that makes sense. It looks pretty likely that a new 12V coil is in order.

Thanks everyone for the help!

Dave

Armed with the information I have been provided and found elsewhere on this forum, I did a little more checking. I removed the distributor and took it inside to work on it. I checked the resistance of the coil and it read 2.3 ohms. The ballast resistor read 1.9 ohms, making a total of 4.2 ohms. 14.5V divided by 4.2= 3.45 That seems just about perfect. The points were nice and clean and the gap was .015 I did all the continuity checks, as listed in another thread and everything was okay there. What I did notice was signs of arcing around the opening for the pigtail on the top of the distributor. The brass screw isn"t centered under the pigtail and I"m guessing was barely making contact. As recommended, I"ve re-assembled the distributor, cap, and coil as a unit, making sure the pigtail is making full contact with the screw head. It was too late to re-install it last night, so I"ll be doing that tonight. Fingers crossed that it starts.....

The 2N is running again! The problem was the coil pigtail not making contact with the distributor screw. Thanks everyone for their advise!

Dave