620 coil

What do I do with wire from starter if I change coil to one with an internal resistor?

For the time being, insulate the end that used to connect to the coil and secure it out of harm's way. If you are satisfied with the new setup you can remove the wire altogether.

This post was edited by wore out on 05/17/2022 at 06:55 pm.

New coil is a 6 volt internal resistor. Not sure why you think it is a 12

(quoted from post at 21:43:55 05/17/22) New coil is a 6 volt internal resistor. Not sure why you think it is a 12

Click to expand...

What is the part number of the coil you purchased from Rock Auto?

Not sure about part number. It is for a 1950 Chevrolet
truck. Go to chrebrolet and truck. 1950 ignition.

IT DEPENDS on your new coil !!!!!!!!

1) A 12 volt tractor like yours came with a 6 volt coil PLUS a series voltage dropping (12 down to 6) ballast resistor and if you want to stay original and need a new coil .... you use a 6 volt coil wired the same. Typically a 6 volt coil HAS NO INTERNAL BALLAST.

2) If you don't want to use the voltage dropping (12 to 6) ballast resistor THEN YOU NEED A FULL TRUE 12 VOLT RATED COIL. If so the wire from the ignition switch to the ballast would be replaced with a wire from the same ignition switch terminal DIRECT TO THE COIL thereby by passing the voltage dropping ballast IE you need the full 12 volts on a 12 volt coil NOT have it reduced by the ballast !!!!!

FYI Typical old 12 Volt tractor coils DO NOT HAVE A DISCRETE STAND ALONE RESISITR TUCKED AWAY INSIDE THE CAN. Some call them INTERNALLY BALLASTED although actually there is NO INTERNAL BALLAST the necessary around 3 ohms of LV primary resistance comes solely by the windings resistance

SEEMS LIKE I POSTED THIS TWICE BEFORE but again to help:

A coil labeled 12 Volts for use with (or requires) external ballast IS IN REALITY MORE LIKE A 6 VOLT COIL and needs the ballast like it says or it will overheat !!!!

A coil labeled 6 volts has around 1.5 ohms of LV primary resistance and NO internal ballast

A coil labeled 12 Volts has around 3 ohms of LV primary resistance

YOUR SPECIFIC QUESTION

With an original 6 volt coil on a 12 volt tractor equipped with an external ballast PLUS a ballast by pass when starting feature but you change to a full true 12 volt coil (no ballast used) ............. THE WIRE FROM STARTER SWITCH up to the coil IS NO LONGER USED AND NEEDS TAPED OFF AND INSULATED AND PROTECTED OR TOTAL DISCONNECTED

There ya go I dont know what else to say lol by now you should be an EXPERT on those coils and how to change from a 6 to a 12 volt coil and ditch the ballast. The original 6 volt coil on a 12 volt tractor was to improve cold weather starting via the ballast by pass when cranking but you can get by fine without it BUT YOU NEED A FULL TRUE 12 VOLT COIL no more series ballast which would drop voltage down to 6

John T

I know I should be an expert but Im not. I have heard so many different opinions that my head swims. I wanted to remain original which from what I can determine was a 6 volt coil with an external resistor. This also had a wire that went to starter. My question was what would you do with that wire you went with a 6 volt coil with an internal resistor.

I need to see the part number of the 6 volt coil with an internal resistor you purchased so I can look at the specs, to answer that question. 6 volt coils are wound for 6 volt use, none have resistors in them as far as I know. I looked at Rock Auto and they show no such coil, as I read the descriptions of coils for a 1950 Chevrolet truck they have. It appears they do have a misprint and show one as 12 volt, but if you check the Delco numbers it replaces they are 6 volt numbers, just like the other 1950 truck coils they show.

I believe you got a plain old style 6 volt coil and it needs the ballast resistor and starting bypass wire to be proper on a 12 volt system.

Hey Bob, you're gonna get this, I hope I have helped.

You just posted

I wanted to remain original which from what I can determine was a 6 volt coil with an external resistor.

CORRECT It had a 6 volt coil and the external ballast resistor was to reduce the 12 battery volts down to 6 for a 6 volt coil


You just posted

My question was what would you do with that wire you went with a 6 volt coil with an internal resistor.

The answer I gave above was

THE WIRE FROM STARTER SWITCH up to the coil IS NO LONGER USED AND NEEDS TAPED OFF AND INSULATED AND PROTECTED OR TOTAL DISCONNECTED

If you re read my post above I think it answers all your questions but if not feel free to ask more

Best wishes now

John T

The one I ordered is 6 volt for use with an external
resistor. I have a 6 volt with an internal resistor. They are
common. I am waiting for the ordered one to arrive. I
wanted to know what to do with starter wire if I used the o
e without an external resistor. Probably not making
myself clear on this. When new coil(without resistor)
arrives I will use that

Thank you! I think I am clear on this now. Just a slow learner!

Take a look at the [b:654c4848f0]Lamps and Wiring[/b:654c4848f0] diagram below.



Note the original lead wire (color not specified) to the ignition resistor.

Pure speculation on my part, based on hearsay or old wives' tale, this original bypass wire was designed to provide more [i:654c4848f0]starting power[/i:654c4848f0] directly to the coil.

It only provided more [i:654c4848f0]starting power[/i:654c4848f0] when the starter switch was engaged.

You might consider attaching the lead wire (illustrated in red) from the starter switch to the NEGATIVE terminal on the coil.

Instead, you might also consider removing the lead wire from the starter switch.



Hope this helps.

Nice picture James,

FYI

Pure speculation on my part, based on hearsay or old wives' tale, this original bypass wire was designed to provide more starting power directly to the coil.

Your speculation is indeed CORRECT, it's NOT an old wives' tale lol. The purpose of the by pass wire was to provide unballasted battery voltage direct to the coil when the starter was engaged. When not in place the voltage to the coil with the points closed was reduced due to the I x R drop across the ballast resistor, however, when the starter is engaged the ballast is effectively bypassed with battery voltage sent direct to the coil via that wire !!!!!!!!!!

It only provided more starting power when the starter switch was engaged.

EXACTLY if all the time there would be 12 volts on a 6 volt coil and it would overheat

Nice sparky chatting with you, best wishes keep them pictures coming

John T

(quoted from post at 18:43:55 05/17/22) New coil is a 6 volt internal resistor. Not sure why you think it is a 12

Click to expand...

"Not sure why you think it is a 12"

Conversely, I'm not sure why you would think your "6 Volt coil" has an internal resistor?????

All the six volts carried by Napa etc are internal resistor. I
had to get one for a 1950 Chevy truck that had no
resistor.

Bob, where do you live?

(quoted from post at 10:41:49 05/18/22) All the six volts carried by Napa etc are internal resistor. I
had to get one for a 1950 Chevy truck that had no
resistor.

Click to expand...

"All the six volts carried by Napa etc are internal resistor."

Mr. Grimes, you are free to have your OPINION and to post it here, but that doesn't make it a "fact".

Rest assured there's NO "resistor" in a common, modern, 6 Volt ignition coil you bought at NAPA.

Or in any coil be it 6 or 12 volts There just made to work on either 6 or 12 volts no internal resister in any of them

Well Im not trying to start an argument. I am just going
by what the coil says on the outside. Not an opinion. I am
no expert by any means. Quite the opposite.

There just made to work on either 6 or 12 volts no internal resister in any of them

EXCEPT FOR THE ONE PICTURED

However, Ive NEVER EVER seen one of those on any old farm tractors

Fun sparky chatting take care everyone

John T

I doubt you bought one of these old coils at NAPA (but hey its possible they were made for some old cars???) THAT DID INDEED HAVE AN INTERNAL RESISTOR

John T

Yes there where some decades ago but I dare you to go out and buy one today

Hey don't be hard on yourself, at my age Im an even slowerrrrrrrrrrr learner lol

Best wishes

John T

[b:654c4848f0][i:654c4848f0]Your speculation is indeed CORRECT, it's NOT an old wives' tale lol[/i:654c4848f0][/b:654c4848f0]

Thanks for the information.

[b:654c4848f0][i:654c4848f0]keep them pictures coming[/i:654c4848f0][/b:654c4848f0]

Take a look at the photos below.



Note the side terminal on the starter switch.



Note the black wire connected to the side terminal on the starter switch leading to the ignition resistor.



Note the black wire from the starter switch connected to the output terminal on the ignition resistor.

When you press down on the starter pedal, 12 volt power temporarily goes directly from the battery to the ignition resistor and coil at start up.

Take a look at the diagram below.



If the ignition switch is [b:654c4848f0]ON[/b:654c4848f0], then once you release the starter pedal, the power comes from the ignition switch to the ignition resistor and coil.

Using a good ohm meter, measure resistance across the primary coil winding (the + and - terminals) and post the results. Then our experts can tell you what you have. And the confusion can hopefully be ended.

Bob, as you noticed folks tend to get their drawers in a wad over this.

Technically they are right but realistically you are. All the ballast resistor is a different wire wound around the ceramic to drop the voltage. The no external resistor needed puts the extra wire inside the can to drop the voltage. Outside it's a resistor but inside its just magic. Clear as mud? Lol

More good pictures..Thanks. Here's a bit more and my take for those who may not yet understand ITS NOT A WIVES TALE LOL

Indeed the ONLY time the ballast by pass circuit functions is when the starter is engaged...

When the start switch is depressed the SMALL starter switch terminal sends unballasted battery voltage direct to the coil SO ITS NOT PASSING THROUGH THE BALLAST AND SUBJECT TO ITS (12 to 6) VOLTAGE DROP

When the ignition switch is on battery voltage is fed to the ballast and when the points are closed and the coil conducts current around 6 volts are dropped across the ballast leaving 6 volts for the 6 volt coil AGAIN HOWEVER ONLY when the start switch is depressed unballasted battery voltage (via the small black wire) is sent do the coil but its not subject to the 6 volt drop across the darn ballast !!! That is to improve cold weather starting when battery voltage can drop dramatically causing a weaker spark !!!

Now if we are helping and not confusing the original poster.....If so he can post questions

Fun sparky chatting with you, best wishes

John T

Its just that (in typical old farm tractor coils) THERE IS NO DISCRETE STAND ALONE RESISTOR TUCKED AWAY INSIDE THE CAN. The 1.5 ohms of LV primary winding resistance is derived solely from the WIRE itself NOT wire PLUS an internal RESISTOR.

AGAIN they did make coils that indeed did have an internal resistor in the bottom of the can but I have NEVER SEEN OR HEARD of any on old farm tractors and I bet NAPA or Deere or IHC or TSC DO NOT STOCK ANY COILS WITH INTERNAL RESISTORS !!!!!!!

Fun sparky chatting with you I hope this helps

Best wishes now take care

John T

It appears at least some NAPA 6 volt coils now have "6 V NO EXTERNAL RESISTOR REQUIRED" printed on them now. The no external resistor required statement applies when the coil is used on a 6 volt system, not when it is used on a 12 volt system. If used on 12 volts, like your 620, it needs a resistor.



A 12 volt coil that is properly wound for a 12 volt system will say "12 V NO EXTERNAL RESISTOR REQUIRED".



A 12 volt coil, wound as 6 volt but intended to be used on a 12 volt system, like your 620 which has an external resistor, would be labeled "12 V USE WITH EXTERNAL RESISTOR".

Those pictures are CORRECT and how Deere and other manufacturers designed their:

Straight 6 Volt,,, Straight 12 Volt,,,,,,,,,,,,And 12 Volt systems that used a 6 volt coil plus an external
series ballast with a ballast by pass when starting option

Those pictures should help the original poster

John T