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Ford 9N, 2N & 8N Discussion Forum

ARRGGHHH!! Now What?

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jfpjr

09-28-2007 17:20:22

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9N. Converted to 12V. Not sure if it is 12V or 6V coil. Square, made in Taiwan, stamped with an A.
Anyway, I had the OEM resitor and a 1.2 Ohm power resitor in line. I burned up the OEM and I assume it is because I had it wrapped with electrical tape. So, hoping I had a 12 V coil (the guy told me it was) I just bypassed the OEM. Now the power resitor burned up. It was not taped up. I took the coil out and checked the primary and secondary coils with an ohmeter. Through the primary reads about 1.4 ohms. From Primary to Secondary reads 9.2k ohms.
I would assume I should not be able to read between pri and sec. Do I have a shorted coil? It apparently did not burn open.
I need to know what parts I need to pick up. I will do some amp checking once I get it close again.
It was running when these burned up, both times.
Thanks in advance

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JFPJR

09-30-2007 06:02:42

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Re: ARRGGHHH!! Now What? in reply to Bob, 09-28-2007 17:20:22

Phil (NJ,Az,Sask) said: (quoted from post at 02:57:35 09/30/07)
[quote:55bf9e95b6]Did a check, 3.3 amps in circuit not running.
So I guess I need to know if this is enough for a 12V coil. [/quote:55bf9e95b6]

I don't know how you measured 3.3 amps but the two resistors you have in series equal a total of only 1.25 ohms (.625 ea) if you have a 2.5 ohm coil. You do not want more current as you now have 3.9 amps running

Something is odd! Measure the COIL and each of those resistors.

You should not sub a fixed Resistor for the OEM ballast.

Reducing Resistance increases Current and you already have enough or to much.

Its your Tractor/coil

JMHO

Actually, if I had 1.25 plus the 2.5 of the coil and around 13 V for battery voltage it would be about 3.47 Amps.

But in actuallity I have 1.5 (two in series, one is .5, the other is 1) I end up with 4 ohms total which gives me 13/4=3.25Amps.

But I measured it for accuracy like this, I put my meter in line in the circuit, set to amps, and read 3.3 amps.

I measure the voltage drop now and I am dropping over 4 volts at the resitors (total). I only have about 8 Volts at the coil.
My question now is this, shouldn't a 12V coil have more than 8 Volts?

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jfpjr

09-29-2007 18:11:34

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Re: ARRGGHHH!! Now What? in reply to jfpjr, 09-28-2007 17:20:22

Coils was bad i think. Assuming it was a 12V coil. I bought a new 12 V coil and it has 2.5 ohm pri resistance. It was even printed on a label.
The same Taiwan and same "A" stamp was on it so I assume my old one was a 12 like this one and developed a short.
So anyhow.
I already burned up mu QEM and did not feel like waiting (field to hog ya know), off to Rural king I go. I buy 2 resistors, and a 12 V square coil.
I hooked them up in parallel but got scared before I started it and switched to series. Did a check, 3.3 amps in circuit not running.
So I guess I need to know if this is enough for a 12V coil. It doesn't seem to start as well as it did, but it sure runs good. It has to crank about 4 seconds to start. Before it would start at about 1 or 2 seconds crank time.
Could it be I have dropped too much E with my series resistors?
I forgot to check coil voltage, but theoretically I am only getting 8.25 volts at 12V batt voltage, which probably drops quite a bit while starting.
I think I may go to one resistor. I just do not know the amp rating on these 8N power resistors. I know 2 in series did not even get warm after an hour of hogging.
Thanks for all the help guys.
No I am having top rpm issues.
Too low. I think I may need to adjust a spring. Not sure. That IT manual doesn't say what to do for low RPM's.

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Phil (NJ,Az,Sask)

09-29-2007 18:57:35

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Re: ARRGGHHH!! Now What? in reply to jfpjr, 09-29-2007 18:11:34

[quote:ef6f97461e]Did a check, 3.3 amps in circuit not running.
So I guess I need to know if this is enough for a 12V coil. [/quote:ef6f97461e]

I don't know how you measured 3.3 amps but the two resistors you have in series equal a total of only 1.25 ohms (.625 ea) if you have a 2.5 ohm coil. You do not want more current as you now have 3.9 amps running

Something is odd! Measure the COIL and each of those resistors.

You should not sub a fixed Resistor for the OEM ballast.

Reducing Resistance increases Current and you already have enough or to much.

Its your Tractor/coil

JMHO

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Jack - Illinois

09-29-2007 01:58:47

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Re: ARRGGHHH!! Now What? in reply to jfpjr, 09-28-2007 17:20:22

Sounds like you have some electrical background, so know how to figure ohms, amps,etc. That said, the wire wound OEM resistor has less resistance when cold to give a boost to starting voltage at he coil output. This helps starting as battery voltage drops somewhat when the starter is engaged. After the engine is running the alternator or generator starts charging and battery voltage goes up. That OEM resistor heats up to a burn the finger temperature which causes it to gain resistance to compensate for this rise in battery voltage. This is designed to prevent the coil from overheating and shorting out some of the primary windings in it. Do not wrap the OEM resistor in anything - it is make to be air cooled. Considering this variable and the size of leads on your meter plus and corrosion or dirt on connections it is difficult to get a meaningful measurement of ohms. Volts at the coil primary seems to be more acurate but this value will also change as the ballast resistor heats up.

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Hobo,NC

09-28-2007 18:46:28

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Re: ARRGGHHH!! Now What? in reply to jfpjr, 09-28-2007 17:20:22

Another way to take care of the problem

Gut'n A coil

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Bob

09-28-2007 17:50:08

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BAD coil??? in reply to jfpjr, 09-28-2007 17:20:22

The primary windings ARE interconnected, a sort of "autotransformer".

The resistance readings REALLY don't prove much, as even a single shorted "turn" will GREATLY decrease spark output while affecting the resistance readings almost imperceptibly.

The "trick" is to use enough resistance to limit primary current (engine stopped, points closed) to a little over 3 AMPS, absolutely NOT exceeding 4 Amps.

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jfpjr

09-28-2007 18:10:47

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Re: BAD coil??? in reply to Bob, 09-28-2007 17:50:08

Thanks.
OK, so if I am shooting for 3.5 Amps, my math shows I need a total of 3.42 Ohms resitance. So if my coil resitance is 1.4, I need a resitor of about 1.8.
Does that sould about right?
I had about 1.1 on it, which theoreticaly would have put me at about 4.8. But while charging the battery is probably higher, around 13.5 maybe? So now we have 5.4 amps. Which in turns gives me about 73 watts. Would that burn up my resitor. I am not sure of the rating on it.
Any of that make sense?

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Dunk

09-28-2007 17:24:00

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Re: ARRGGHHH!! Now What? in reply to jfpjr, 09-28-2007 17:20:22

I hope you have a better one tomorrow, jfpjr!!!

Got any beer or whiskey??

It makes me feel better..

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jfpjr

09-28-2007 17:35:55

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Re: ARRGGHHH!! Now What? in reply to Dunk, 09-28-2007 17:24:00

I am sure I have a little Crown sitting around....

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Phil (NJ,Az,Sask)

09-28-2007 18:33:18

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Re: ARRGGHHH!! Now What? in reply to jfpjr, 09-28-2007 17:35:55

Buy yourself 1 OEM Ballast, and 2ea 1.2 ohm Fixed resistors.

Math: 14.5V/3amps = 4.83 ohms total for FM coils

The OEM Ballast is 1.5 ohms @ 3 amps.

The Coil Primary is near 1.2 Ohms.

1.5 OEM ballast,+ (plus)1.2 fixed, + (Plus) 1.2 Fixed = 3.9 ohms, + (plus)1.2 Coil = 5.1 ohms
That is close enough for the 6 volt Coil.

Your Coil may be damaged NOW but you obviously
know how to measure the Resistance of a Replacement.. 12 volt coil will be ~2.5 Ohms and
removing 1 ea of the 1.2 ohm fixed will get you
close @ ~5.2 ohms.

BTW: The OEM Ballast Limits Current and will burn out if current goes beyond ~ 3.3 amps.

Hope This Helps,

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don b

09-29-2007 06:27:00

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Re: ARRGGHHH!! Now What? in reply to Phil (NJ,Az,Sask), 09-28-2007 18:33:18

Phil..... you say....."12 volt coil will be ~2.5 Ohms and
removing 1 ea of the 1.2 ohm fixed will get you
close @ ~5.2 ohms."
I think this is bad info.The so called 12v coil could have from 1.2 ohms to whatever.He should measure the primary resistance on ANY coil he buys. don b

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jfpjr

09-28-2007 18:52:28

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Re: ARRGGHHH!! Now What? in reply to Phil (NJ,Az,Sask), 09-28-2007 18:33:18

So all three resitors in series? I haven't seen that diagram anywhere on here. Maybe time for someone to update the diagram.
Thanks

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Phil (NJ,Az,Sask)

09-28-2007 21:35:49

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Re: ARRGGHHH!! Now What? in reply to jfpjr, 09-28-2007 18:52:28

[quote]So all three resitors in series? I haven't seen that diagram anywhere on here. Maybe time for someone to update the diagram.[/quote]

For a 6 Volt Coil YES all 3 in series (they ADD)

For a 12V coil you only use the OEM Ballast, + (Plus) 1.2 OR... for better starting OEM Ballast, + Plus both 1.2 Fixed resistors in Parallel (side by Side) =.6 ohms. 2.5 + 1.5 +.6 = 4.6 Ohms

The total NUMBER is 4.83 (Ideal if all faults are corrected) but for your/my own tractor close is good enough 4.0 or 5.0 will work just fine.

The "KEY" is the OEM Ballast!

JMHO

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Dunk

09-28-2007 18:57:51

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Re: ARRGGHHH!! Now What? in reply to jfpjr, 09-28-2007 18:52:28

I might could help, ifn you would return it to stock.

12 volt N tractor...

WHY!?!?!?!?!?

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old 9

09-28-2007 19:38:02

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KISS in reply to Dunk, 09-28-2007 18:57:51

One more reason to " Keep It Stock" Stupid If it is stock all you have to do is look it up in the manual.

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jfpjr

09-28-2007 19:07:08

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Re: ARRGGHHH!! Now What? in reply to Dunk, 09-28-2007 18:57:51

Half done when I got it. No genny.

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