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Coil question


101Pathfinder
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Ok - Gotta admit I'm not an electrical guy...

I bought an internally resisted 12V coil to replace the old coil and external ballast resistor. (Along with some other parts - plug wires, new dist cap / rotor, points and condenser...)

There is one wire from the solenoid to the negative side of the coil. There's also a wire from the ignition sw (IGN) that sends voltage through the ballast resistor to the

negative side of the coil. (I understand what the ballast resister does to help prolong the life of the points) When I remove the original coil, should I connect both wires (wire from IGN and wire from the solenoid) to the new internally resisted coil? (of course eliminating the external resister)

Thanks in advance - Mike

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Not certain, but I believe:  Connect both - ....but to + side of coil (- goes to points {usually} unless positive-ground system?).  2nd wire (solenoid) won't do a darn thing, though, with no external resistor:  Normally, the key/button "start" position bypasses the resistor (via the solenoid wire) to give "full power" to the coil during startup; then when you release (key/button) to "run" position, the bypass goes away and the main (Ignition) wire supplies the coil through the resistor (so it doesn't fry).

 

M

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10 hours ago, DT361 said:

Not certain, but I believe:  Connect both - ....but to + side of coil (- goes to points {usually} unless positive-ground system?).  2nd wire (solenoid) won't do a darn thing, though, with no external resistor:  Normally, the key/button "start" position bypasses the resistor (via the solenoid wire) to give "full power" to the coil during startup; then when you release (key/button) to "run" position, the bypass goes away and the main (Ignition) wire supplies the coil through the resistor (so it doesn't fry).

 

M

Thanks DT361... I meant to include that this tractor has been converted to a 12V negative ground but left out that information.

That's why I stated those connections go to the - side of the coil...

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I would go ahead and correct the polarity to your new coil.  Whereas the coil would likely generate a spark if reversed, the internal windings won't be particularly "happy" with the current flowing in the opposite direction of how they are designed/wound.

 

Just my $0.02.

 

Mark

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What tractor do you have ?   I am figuring key or push button starting, like a Farmall 400 or 450. Does the solenoid have two (small) terminals "S" and "I"? Since you have a coil with added resistance, no ballast resistor is needed.

Negative ground system coil:  Positive from ignition switch and negative to distributor.

S terminal: voltage applied here engages the solenoid to run the starter. From ignition switch or button.

I  terminal ( if there) is ignition bypass and goes directly to the coil to provide full cranking voltage for better starting.

 

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Hey Tom... Thank you for the reply!

This is a '57 Farmall 350 gas... Using a starter switch - teminals are IGN / Batt / ST / ACC. The solenoid has both an "S" and "I" terminal. This tractor was converted to 12V negative ground years before I purchased it.

Just trying to upgrade the machine somewhat. Put on new brake discs, hydraulic and radiator hoses, new ignition sw, and other parts.

When it became mine it had the original coil and external resister on it so may be a 6V coil - which is ok, but, as I stated, just wanting to upgrade some parts to the 12V system and get it back in the hay raking business - then put my MF 35 in my shop for some needed attention.

Appreciate all the information I can get - It's a cool old tractor.

Mike

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1 hour ago, Moodnacreek said:

6V does not use a resister . The resister was on there for 12V as the points want to be 6V. A hot wire from ign. switch goes on + coil terminal and a wire on the other [-] coil terminal goes on distributor.

Roger that...

But... On the new coil should I connect both wires (wire from IGN and wire from the solenoid) to the new internally resisted coil?

 

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25 minutes ago, 101Pathfinder said:

Roger that...

But... On the new coil should I connect both wires (wire from IGN and wire from the solenoid) to the new internally resisted coil?

 

You can if you wish but it won't do anything. Won't hurt anything either.

Do correct coil polarity.

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45 minutes ago, snoshoe said:

...won't do anything.

Actually, - it does do one thing:  It anchors an "occasionally live" positive conductor to a fixed point so it isn't likely to short to ground accidentally. 

Otherwise, you should zip-tie/tape/protect/insulate that terminal ring in some effective manner.

 

M

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On 6/17/2021 at 8:20 PM, 101Pathfinder said:

Ok - Gotta admit I'm not an electrical guy...

I bought an internally resisted 12V coil to replace the old coil and external ballast resistor. (Along with some other parts - plug wires, new dist cap / rotor, points and condenser...)

There is one wire from the solenoid to the negative side of the coil. There's also a wire from the ignition sw (IGN) that sends voltage through the ballast resistor to the

negative side of the coil. (I understand what the ballast resister does to help prolong the life of the points) When I remove the original coil, should I connect both wires (wire from IGN and wire from the solenoid) to the new internally resisted coil? (of course eliminating the external resister)

Thanks in advance - Mike

These are wired with 12v switched to the resistor. From on/off switch.

Then the other resistor terminal to the plus side of the coil with the coil negative to the distributor. (Assuming negative ground)

Then run a wire from the solenoid terminal, which is given 12v to the solenoid to engage the solenoid from start push button.

That wire goes to the resistor screw that goes to the distributor.

This gives a full 12v as a boost to start the engine.

When you let off the starter, the power then goes through the resistor and saves your points.

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7 hours ago, Diesel Doctor said:

These are wired with 12v switched to the resistor. From on/off switch.

Then the other resistor terminal to the plus side of the coil with the coil negative to the distributor. (Assuming negative ground)

Then run a wire from the solenoid terminal, which is given 12v to the solenoid to engage the solenoid from start push button.

That wire goes to the resistor screw that goes to the distributor.

This gives a full 12v as a boost to start the engine.

When you let off the starter, the power then goes through the resistor and saves your points.

I never thought to do it this way and it requires the non resistor coil.

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18 hours ago, 101Pathfinder said:

Roger that...

But... On the new coil should I connect both wires (wire from IGN and wire from the solenoid) to the new internally resisted coil?

 

Mike,

First off, upload a profile pic. This place needs some pathfinder wings.... ?

Second, the wire from the ignition switch and the solenoid are a parallel circuit. Both are supplying 12VDC to the coil. The IGN circuit is constant while the solenoid circuit is momentary. You could disconnect one end or both ends of the solenoid wire, or remove it all together if it's not part of a harness. All you need after the 12V negative ground conversion and your new internally resisted coil is a constant 12VDC from the switch to the coil.

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3 hours ago, messer9696 said:

Mike,

First off, upload a profile pic. This place needs some pathfinder wings.... ?

Second, the wire from the ignition switch and the solenoid are a parallel circuit. Both are supplying 12VDC to the coil. The IGN circuit is constant while the solenoid circuit is momentary. You could disconnect one end or both ends of the solenoid wire, or remove it all together if it's not part of a harness. All you need after the 12V negative ground conversion and your new internally resisted coil is a constant 12VDC from the switch to the coil.

Hey messer9696!!

After VietNam I went to Ft Bragg / 18th Corps... 82'd soldiers are among the finest!!

I believe I was over complicating the whole thing. I removed the connection to the solenoid and just used the batt power from IGN on the switch this morning.

Thanks for the advice...!!! I tend to be OCD on too many things - LOL!

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On 6/20/2021 at 7:09 PM, 101Pathfinder said:

Hey messer9696!!

After VietNam I went to Ft Bragg / 18th Corps... 82'd soldiers are among the finest!!

I believe I was over complicating the whole thing. I removed the connection to the solenoid and just used the batt power from IGN on the switch this morning.

Thanks for the advice...!!! I tend to be OCD on too many things - LOL!

I'm glad you got her running!

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