Resistor/Coil

I did a 12V conversion last weekend. (Please no debate on that--I did it because my voltage regulator was toast. And since there's no power out at my cabin, it's a whole lot easier to boost the tractor off of my truck, than to haul out a generator and battery charger...)

Anyway, in hooking up the new wiring harness (which fit awesome, BTW), I apparently wrecked the resistor on the terminal block. A new one is on order and should be here in a week or so (depending on the postal system--my last order took three weeks, but it was very heavy).

So my question is: In the meantime, is it safe to run the tractor for a short time without it? How long is too long? I don't want to fry my nice new 12V coil...

Thanks,

-Paul
 
My story is that any time will be hard on the points. Coil?....Probably plenty safe for 30 seconds, maybe 60, but after that you gamble. Never intentionally burned one up, so can't give a definitive answer. Maybe soon you will be able to tell us how long. If it were not the square can epoxy/tar filled coil, but a round metal can, oil filled unit, I wouldn't feel bad about an hour.
I have read two posters claims of doing what you want with the sq coil for years ..........but those are "claims". Maybe if never stall it?
 
(quoted from post at 17:06:23 05/17/16) My story is that any time will be hard on the points. Coil?....Probably plenty safe for 30 seconds, maybe 60, but after that you gamble. Never intentionally burned one up, so can't give a definitive answer. Maybe soon you will be able to tell us how long. If it were not the square can epoxy/tar filled coil, but a round metal can, oil filled unit, I wouldn't feel bad about an hour.
I have read two posters claims of doing what you want with the sq coil for years ..........but those are "claims". Maybe if never stall it?

i don't know about the difference between no working OEM ballast resistor and no additional "white ceramic blob" resistor (lol, love that term :) ), but i'll add this to the discussion.

my 2N was converted to 12 volts and has seen 3 full years of use since then, with no white ceramic blob. at the time of the conversion, i knew nothing about the coil issue, and so i had no concerns about it.

but, since having read as much as i can of the wealth of info here over the last 6 months, i now understand i'm risking the health of my 6v square coil (and points too?), and i will get around to reinstalling the blob with a cutout switch on it for starting.

in the meantime, on a normal basis, this tractor gets used for an hour or 2 once a week. minimum use time would be around 30 minutes without shutting down for a break, an hour is the norm. that's not to say that i could get away with this forever - for all i know, it won't fire the next time i try to start it, but so far so good.
 
" and i will get around to reinstalling the blob with a cutout switch on it for starting."

Seriously? That's cheaper & easier than installing a 12 volt coil & OEM ballast resistor?
75 Tips
 
(quoted from post at 17:27:40 05/17/16) " and i will get around to reinstalling the blob with a cutout switch on it for starting."

Seriously? That's cheaper & easier than installing a 12 volt coil & OEM ballast resistor?
75 Tips

yes, seriously :)

cheaper? since i already have the white blob, the wire, connectors, and the switch, i'd say my plan can't be more expensive, since it's free.

easier? offhand, i'm guessing yes. i am not sure what exactly needs to be done to gut the existing square coil to bypass it, but i know how easy it is to run a wire with a switch on it.

ps: the OEM resistor (freshly replaced when i did the rebuild) has been in use the whole time. i think u must have misunderstood me.
 
(quoted from post at 17:44:34 05/17/16)
ps: the OEM resistor (freshly replaced when i did the rebuild) has been in use the whole time.

duh, mistyped there. freshly replaced when i did the conversion, not the rebuild, which was this winter.
 
" i think u must have misunderstood me"

No, I think you misunderstood me.

If you have a 12 volt coil, all the resistance you need is in the OEM ballast resistor. There is no need to add a ceramic resistor, much less a switch.

And.....

If you are going to use a side coil, most of them need no resistors at all.
75 Tips
 
(quoted from post at 17:54:15 05/17/16) " i think u must have misunderstood me"

No, I think you misunderstood me.

sorry, i took this:

"installing a 12 volt coil & OEM ballast resistor"

to mean u thought i didn't already have an OEM ballast resistor in use.

i do not have a 12 volt coil. i understand it needs no additional resistance, and if i had one laying around, that's what i'd do. but i don't have one.
 
" but i don't have one."

Fine.

But why a switch?

With a 6v coil, use the OEM ballast resistor, which you have, and a ceramic resistor of (usually) 2 ohms. Why the switch? It will start just fine w/ a 2 ohm resistor & the OEM ballast resistor.

What is the value of your ceramic resistor?
75 Tips
 
(quoted from post at 14:06:23 05/17/16) My story is that any time will be hard on the points. Coil?....Probably plenty safe for 30 seconds, maybe 60, but after that you gamble. Never intentionally burned one up, so can't give a definitive answer. Maybe soon you will be able to tell us how long.

Okay! I won't be running it until the resistor arrives! I did start it to make sure it would start and give good voltage at the battery--both passed with flying colours, but I didn't run it more than 10 seconds.

BTW, what is the resistance of the resistor on the terminal block, anyway? (And is it the one with different hot and cold resistances?)

Thanks,

-Paul
 
(quoted from post at 18:09:57 05/17/16) " but i don't have one."

Fine.

But why a switch?

With a 6v coil, use the OEM ballast resistor, which you have, and a ceramic resistor of (usually) 2 ohms. Why the switch? It will start just fine w/ a 2 ohm resistor & the OEM ballast resistor.

What is the value of your ceramic resistor?
75 Tips

my best guess is 2 ohms, but that's a guess. if i try checking it with my cheap digital meter, i get 6 ohms or 1 ohm, depending on which scale i use. if i check it with my analog meter, i think it's 2, but the needle is moving around in a manner that erodes my confidence in the reading.

the ceramic blob came with the rebuild kit. the tractor would not start with it in use, and started fine as soon as it was removed.
 
"What's the resistance of your coil? 1.7 on the OEM ballast resistor, 3.5 on the ceramic resistor, you're already at 5.2 ohms"

now that i have figured out i actually have a meter i can probably trust for ohms (only thought of the fluke as my a/c ammeter), i'll be happy to check (hokie, i didn't say ohm, you've trained me well. one success story in a sea of likely failures :) ) anything and everything on the beast. please refresh my memory, for the coil i'm reading from the top screw to where?

and how many ohms total should there be when added up?
 
(quoted from post at 18:37:06 05/17/16) The OEM ballast resistor is .03 ohms cold
and 1.7 ohms red hot. Most folks figure 1
ohm hot.
75 Tips
ep, burn you finger hot or light paper hot. 1.7 will light paper. Furthermore, any Ohmmeter measurement is so highly variable, depending on technique & how you hold your tongue that I wouldn't put faith in anyone's measurement but my own & then only if repeatable. For those very low resistances, I run a measured current through the resistor while measuring voltage across it and divide V by I.
 

i sincerely hope to never see my OEM resistor glowing. in any event, i think i may never touch the thing again ;)

understand the concern about readings. in this case, repeatability is a non-issue, the thing has a pair of spade lugs with holes in them. i can put the probes thru the holes and just exert force outward, and i get 3.5 every time i try.
 
" for the coil i'm reading from the top screw to where?"

Top of the coil to the pigtail on the bottom.


" and how many ohms total should there be when added up? "

It's not the ohms, it's the amps.

The OEM 6v coil spec was .47 to .51 ohms. With a 6.35 volt battery & a .03 cold ballast resistor, starting current was about 8 amps.

Running current, at 7.35 volts & a max of 1.7 ohms in the resistor, running current was about 3.5 amps.

Add as much resistance as needed to get you to less than 4 amps running current & about 7-8 amps starting current.
75 Tips
 

"Add as much resistance as needed to get you to less than 4 amps running current & about 7-8 amps starting current."

how much resistance is that?
 
" how much resistance is that? "

Until you measure the resistance in the coil, we won't know.

Right now, the only known constants are the value of the OEM ballast resistor, the ceramic resistor & the voltage. In order to figure it out, you need to determine the coil resistance and do the math.
75 Tips
 

when adding up the resistance of coil, OEM resistor, and ballast resistor (if present), what should the total be? correct me if i'm wrong, but wouldn't this targeted total number of ohms be a well known number for this situation?
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top