2N Low Power = Weak spark

TB in MN

Member
1947 2N Front Mount Distributer 12V –Ran low on poweer after disking for a couple hours last weekend.

Checked points as advised and found no problems. Fuel flow was fine from bottom of the carb. Found weak spark with adjustable spark checker. Charged battery and started up and ran good. Disked another 45 minutes before it started running rough just as before.

Found weak spark again. Pulled battery and alternator to have checked. Alternator checked fine. Battery checked bad.
Ran great again with new battery until it started running poorly again after another hour disking.

Fuel flowed freely again from bottom of carb. Charged new battery a couple hours. Tried again and it still ran poorly before parking it for the night.

Why would tractor repeatedly have weak spark after working it roughly an hour? Amp meter showed about 5 amps while it was working. What next?

Thank you,
TB in MN
 
TB.........ummm? Do you see enny correlation between weak sparkies and dead battery??? While the 4-nipple front mount isn't known fer being a real dynamo of sparkies, the squarecan coil can run fer about 1-hr before the internal insulative tar melts and shorts out the windings. Cooling off overnite will let you run fer about 1-hr the next day. Make certain yer points are gapped 0.015". .......HTH, Dell, yer self-appointed sparkie-meister
 
(quoted from post at 02:32:40 05/23/15) 1947 2N Front Mount Distributer 12V –Ran low on poweer after disking for a couple hours last weekend.

Checked points as advised and found no problems. Fuel flow was fine from bottom of the carb. Found weak spark with adjustable spark checker. Charged battery and started up and ran good. Disked another 45 minutes before it started running rough just as before.

Found weak spark again. Pulled battery and alternator to have checked. Alternator checked fine. Battery checked bad.
Ran great again with new battery until it started running poorly again after another hour disking.

Fuel flowed freely again from bottom of carb. Charged new battery a couple hours. Tried again and it still ran poorly before parking it for the night.

Why would tractor repeatedly have weak spark after working it roughly an hour? Amp meter showed about 5 amps while it was working. What next?

Thank you,
TB in MN

TB, Bruce and many other experts here are real good at figuring out problems. I just wanted to share with you a recent problem I had on My 93 F350 truck. It had started to show by the gauge in the truck weak charging of the battery I checked it was down to 12.2 volts new battery should be at 12.6 then the next day over charging. I checked it with a multimeter its over charging its reading 17-18 amps I removed the alternator had It checked at the local yep you guessed it auto zone they said it checked good. This is an internally regulated alternator, Well I could not believe it I bought a new regulator anyway very simple on this truck to remove and install problem fixed. I let them know there machine could not detect A bad regulator. You may not even have an internally regulated alternator on your tractor it may not have any thing to do with your issue just don't trust some of these auto part store checks.. My opinion is Check it yourself and go with what you know.
 
Now it makes more sense…A couple weeks ago I left the tractor idling at a slow idle while I did something else. It eventually died and I forgot to key it off. I replaced the points but neglected the coil. Today I pulled the coil and measured .4 ohms across it so it seems to be to be internally shorted. Best I can measure, it has a 1.8 ohm resistor in series with it. I found only one other coil in town which measures 1.0 ohms. Also found .6 ohm resistors.

From reading the archives seems I need to target 3.5 amps. Alternator voltage = 14.5 volts. R=V/I=14.5/3.5=4.14ohms is the total resistance I need to target right? 1 Ohm coil + 1.8 Ohm old resistor+ .6 ohm new resistor+.6 ohm new resistor = 4.0 ohms. 14.5V/4 ohms = 3.6 amps. Will it work if I connect all three resistors in series or am I off base? Cobble job I know, but I don’t want to have to wait for parts in the mail.

Thank you,
TB in MN
 
But didn't I see you, Bruce, advocating in previous posts using a 6V coil in a 12V application with the addition of resistors to make up for the lower resistance of the 6V coil? By doing this heat buildup is moved out of the coil to lessen the chance of the coil failing.

TB in MN
 
" But didn't I see you, Bruce, advocating in previous posts using a 6V coil in a 12V application with the addition of resistors to make up for the lower resistance of the 6V coil?"

Yes.

And if I had a 12v N w/ a 6v coil, that is exactly what I would do, because I know how to do it.

But, as I said in tip # 30, must folks do not have the time & interest to do that & consequently end up w/ too much or too little resistance & a poorly running tractor.

Sounds to me that you do know what you're doing. Just buy the correct resistor(s)and crimp the connections.
75 Tips
 
I only know enough to be dangerous since I've recently been reading up on my current problem.

There must be some tradeoff in using a lower resistance coil in a 12V application? Otherwise, it seems there would be no need for a different coil for 12V applications. Only higher resistance resistors would be needed.

TB in MN
 

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