[hilsenteger]

Morning,

I created this post yesterday https://www.greentractortalk.com/threads/3020-gas-resistance-wire.211564/ and had some discussion going, but this morning the post is gone. Not sure what happened - I can find it listed on Google, but not here. So I'm going to recreate it best I can, assuming that there wasn't a reason that it was removed.

Long and short:

• 3020 gas synchro range (1967) positive ground tractor
• had a wire fire - cut replaced the damaged wires by cutting back to the wiring harness, and used the stubs of the wires to butt-connect new wires to.
• I was emailing back and forth with Agri-services about a replacement wiring harness, was told that there is a 7-foot long "resistance wire" going from the harness (ignition switch) to the coil, and that if I have the coil connected directly to the 12 pin connector without the resistance wire, I will have battery voltage at the coil and the points, which will usually burn out the points, condenser and possibly the coil.
• When I asked what I needed to do to address this, he told me that I'd need to put in an ignition resistor of at least 1.6 ohms. This is regardless of if I rewire it, or if I buy their harness, because they don't use the resistance wire anymore.
• My post was checking in to see if this made sense to folks, because I thought that the internal resistor at the switch reduced the voltage to the 6V coil when the tractor was running so that it didn't burn out the points, condenser, etc., and that the wire that runs between the R post on the starter to the coil was there to provide max power at start up, but only for when the tractor was starting.

I know a couple of people already responded and there was a bit of discussion going on yesterday, but then the post got lost or removed.

Hoping I didn't violate any rules, but I'll try again.

Thanks all!

 

[rwmeyer]

I'm not sure on tractors, but I've worked on a few early Chevy's. I believe the 60 Chevy had a ballast resistor on the firewall between the ignition switch and the coil to drop the voltage while running, an a 64 used a resistance wire. Both had a wire on the R solenoid to provide 12 volts to coil for starting. Some cars use a built in resistor inside the coil.

Not sure about your coil being 6 volts, but I'd remove the wire from the + side of the coil, turn key to "Run" and check voltage from disconnected coil wire to ground. If 12 volts, you'll need either a ballast resistor or resistance wire. If (I believe??) approx. 7-9 volts on coil wire, no resistor needed. I'm totally confused though on why you're have a 6 volt coil in a 12 volt system!

'Bout all I can help with! Bob

 

[Sevenhills1952]

12v battery you'd want a 12v coil. Some coil say internal ballast, others external.
External I'd rather have resistor than resistance wire. One side ignition switch, other side coil + (if negative ground system) as well as a wire to starter so when cranking you get full available voltage, when started voltage drops through resistor.

Sent from my SM-S205DL using Tapatalk

 

[Herminator]

I was one of those responding and thought you deleted the thread because yes, it just evaporated.

Here is what I used on mine for a coil. It has a 1.4ohm internal resistor and you can just run 12v to it.

It is confusing because like you say the manual says it has the resistance wire or a key with it built in. Mine had neither but it was built a long time ago and who know what changed. Mine has 12 volts while the ignition is in start or at the run position.

I don't care for resistance wire for the same reason you are rewiring yours, perhaps unfounded worry but if you can get away from any resistor why not. A resistor is just one more thing in the circuit to troubleshoot and this solution is a solid one.

From Summit Racing or other places ACCEL SuperStock Ignition Coils 8140 pn: ACC-8140.
A 40,000 volt capable coil that is meant to be used with a points set up.

 

[hilsenteger]

12v battery you'd want a 12v coil. Some coil say internal ballast, others external.
External I'd rather have resistor than resistance wire. One side ignition switch, other side coil + (if negative ground system) as well as a wire to starter so when cranking you get full available voltage, when started voltage drops through resistor.

Sent from my SM-S205DL using Tapatalk

Thanks - I think you're right, but right now, my 3020 gas has a resistor built-in to the switch that's supposed to reduce voltage so that it works with a stock 6V coil. So, in my mind, if I put a 12V coil on it, and it's only getting 6V from the ignition switch, it doesn't seem like it would be getting enough juice. If I took out the original switch, then I could see going to a 12V coil. Of course, this all gets even more confusing when the resistance wire gets thrown in there. So, for now, what I think I'm going to do is get out my multimeter and a) check the resistance on my current coil, b) check how much voltage is coming from the two wires going to the coil (one off the ignition switch post-internal resistor and the other off the R terminal at the starter solenoid) and go from there. Hopefully I can sort this out.

 

[hilsenteger]

I was one of those responding and thought you deleted the thread because yes, it just evaporated.

Here is what I used on mine for a coil. It has a 1.4ohm internal resistor and you can just run 12v to it.

It is confusing because like you say the manual says it has the resistance wire or a key with it built in. Mine had neither but it was built a long time ago and who know what changed. Mine has 12 volts while the ignition is in start or at the run position.

I don't care for resistance wire for the same reason you are rewiring yours, perhaps unfounded worry but if you can get away from any resistor why not. A resistor is just one more thing in the circuit to troubleshoot and this solution is a solid one.

From Summit Racing or other places ACCEL SuperStock Ignition Coils 8140 pn: ACC-8140.
A 40,000 volt capable coil that is meant to be used with a points set up.

Thanks for responding again - not sure what happened to the original post - hope it wasn't something I did!

Yup, very confusing. For my tractor, I believe it's got both the resistor at the switch and the resistance wire - something doesn't seem right - time to get the multimeter out.

 

[Herminator]

but right now, my 3020 gas has a resistor built-in to the switch that's supposed to reduce voltage so that it works with a stock 6V coil.

I believe when I looked up at the back of the switch I saw a resistor on it as well. Yet I had 12v at the coil.

check how much voltage is coming from the two wires going to the coil (one off the ignition switch post-internal resistor and the other off the R terminal at the starter solenoid)

Good plan. Then you will know for sure.

 

[Sevenhills1952]

If you have 12 volt battery, you need 12v coil. Points open it will read 12v, closed it will be less.

Sent from my SM-S205DL using Tapatalk

 

[hilsenteger]

Happy Monday!

Spent some quality time with my tractor over the weekend because I wanted to get in there and do some tests to understand how this worked. Got a new multimeter because the one I was using was going all squirrelly when I'd try and test anything when the tractor was running!

First, I tested the resistance across the coil to see if it's 6 or 12V - it tested at 1.6 ohms, so I'm assuming it's a 6V. However, on the coil is stamped "U500". When I looked that up, it shows an old Delco-Remy 12V coil. Hmmmm.... it doesn't say whether it's an internally resisted coil though - anyone know anything about this old coil?

I can also confirm that on my tractor, there is no resistor on my key switch - I thought there was because of the schematic I was reading in the service manual. The resistor I was seeing was on the light switch - just had to get in there and trace things I guess. So, the old resistance wire that went from the ignition switch to the coil is the only resistor in front of the coil. I had cut that out when I rewired the tractor after the fire and replaced it with a 14 gauge wire.

I did some tests on the wires - with the ignition wire attached to the negative lead on the coil and the key on (distributor points closed), I put my negative test lead on the negative post on the coil and grounded the positive test lead. I found that I had 10V at the coil. I realized that I had that stub of resistance wire coming off the harness (butt connected to the new 14 gauge wire) and it was hot! So, I pulled out the length of old resistance wiring out of the trash (it wasn't burned in the fire surprisingly) and reattached it to that ignition wire at the harness and the coil. With that change, I was getting 5.8V at the coil. That lines up with what I my service manual said I should be seeing (5v - 7v with key on, points closed).

Then, I started the tractor - starts on one push of the button - the tractor is running fine - I haven't done anything to the distributor, and haven't for a number of years, so I'm thinking the points are fine. I tested the coil, it showed 11V on the ignition side of the coil and 9.8V on the distributor side of the coil. Does that make sense? Can I test the voltage at the coil with it running? I read somewhere that I can't, but I think that was related using an electronic multimeter. Anyone have any insight here?

Anyhow, long and short, I think I need to get a ballast resistor and get rid of that resistance wire - I don't like the heat coming off of it - I'm thinking that might have contributed to the original wire fire!

Grant

 

[Zebrafive]

My "Guess" is the voltage drop you saw across the coil; 11v to 9.8v is due to the resistance/load of the coil windings.

 

[hilsenteger]

So, quick update - I bought a ballast resistor to get rid of the resistance wire. And, I also finally figured out how to properly test the voltage at the coil with the ballast resistor in place.

The problem I was having, and I read that some others have the same problem, is that they are testing with the points open. With the points open, you'll see battery voltage (12V - 13V) when you test. When the points are closed, you should see a lower voltage (5V to 7V for a 6V positive ground system like mine). The points were open on my tractor, and I didn't know how to close to points outside of bumping the starter until you get to a point where they are closed - seemed kind of random.

Remember - this is for a positive ground tractor, so the polarity might seem weird. But if the points are open, I found out that:

1) run a test wire from the + side of the coil (wire going to the distributor) to a good ground. That's the part I was missing. This will allow you to do the voltage test regardless of whether points are open or closed.

2) connect your voltmeter to the negative side of the coil - negative lead to the - terminal, and positive to a good ground.

3) if you turn on the key and provide power, you should see 5v to 7v on the voltmeter. Mine shows 5.6. I think that's perfect.

I'll send a pic later. Not sure who's reading this anymore, but I hope that my findings help someone and saves them some frustration when testing the ignition system.

I also found an old ammeter on an old wrecked swather in my yard - pulled it off, tested it, then connected it to the tractor, running it between the BAT terminal on the regulator and the negative battery terminal. I started the tractor, and nothing. Guess that explains why the GEN light stays on after the tractor starts. I was excited to see an old alternator on the old swather (Massey), but when I checked the serial number, it turns out that it's a 10DN alternator, with an external generator. Not what I was hoping for. However, I did pull out the mounting bracket and bolts so that might help me when I get a new alternator.

Next is buying an alternator!!

Grant

 

[rwmeyer]

hillsentyeger, You procedure is correct, but something you should add is that you're working with a positive ground system! The + and - of the coil polarity could REALLY confuse some! Bob

 

[hilsenteger]

hillsentyeger, You procedure is correct, but something you should add is that you're working with a positive ground system! The + and - of the coil polarity could REALLY confuse some! Bob

Morning Bob - thanks for the comment - I do say that it's a positive ground system at one point, but I will edit to make it clear - I agree that I have to remind myself which terminal I'm attaching what to when I'm wiring things up!

 

[rwmeyer]

AH, yes! NOW I see it in post #1!

Bottom lune us tractor starts and runs, GOOD JOB !

Alternator with pos ground may be difficult to locate, not sure as I've never looked. Maybe an old Ford automotive alternator? A lot of the old Fords were pos ground.

Best of luck with alternator and keep us posted Bob

 

[hilsenteger]

AH, yes! NOW I see it in post #1!

Bottom lune us tractor starts and runs, GOOD JOB !

Alternator with pos ground may be difficult to locate, not sure as I've never looked. Maybe an old Ford automotive alternator? A lot of the old Fords were pos ground.

Best of luck with alternator and keep us posted Bob

Thanks Bob - yah, I think it was in there originally, but I made a couple of edits to make sure it's clear. I'm trying to help, and I know it's hard to wade through posts where there is incomplete information, so I appreciate the suggestion to make it clearer.

My plan is to get a 70's style 10si three-wire alternator like this:

ACDelco Gold 334-2114 Alternator, Remanufactured, Alternators - Amazon Canada

ACDelco Gold 334-2114 Alternator, Remanufactured in Alternators.

www.amazon.ca

and then rewire things to negative ground. Think I have gleaned the proper way to do that from posts here and other places online, but if I need help, I'll reach out and provide updates!!

Thanks again,
Grant

 

[rwmeyer]

Hmm, Look into that alternator CAREFULLY! That's a DC output and the frame my be (??) the negative. If the frame is insulated/isolated from the windings, no problem! Run positive output to frame/ground and then power system from Neg terminal. If frame is not insulated/isolated, you'll have a neg. voltage going to frame and a pos voltage going to ???.

Partscatalog.deere.com shows a remanufactured alternator... for a 3020... for $153 USD. Might be something to consider! Bob

 

[hilsenteger]

Hmm, Look into that alternator CAREFULLY! That's a DC output and the frame my be (??) the negative. If the frame is insulated/isolated from the windings, no problem! Run positive output to frame/ground and then power system from Neg terminal. If frame is not insulated/isolated, you'll have a neg. voltage going to frame and a pos voltage going to ???.

Partscatalog.deere.com shows a remanufactured alternator... for a 3020... for $153 USD. Might be something to consider! Bob

Thanks Bob - when I do the swap out of the alternator for the generator/regulator, I'm planning to switch the wiring so that the tractor's polarity goes from positive ground to negative ground. I'm thinking that alternator should be ok, i.e. negative ground. Unless I'm missing your point?

 

[rwmeyer]

Do you have a wiring schematic? I'm far from an Electrical Engineer, but have a fair knowledge of electrics. Some DC coils are polarity sensitive, most aren't. It'd be best to review a schematic and determine what coils, motors, gauges, etc. could be affected by changing polarity.

And that was my point, polarity of the regulator in the alternator. Bob

 

[hilsenteger]

Again - appreciate the advice! I do have a wiring diagram. My intent is to reverse the wiring from the battery to the starter (so that the negative terminal goes to ground on the tractor), and to reverse the wiring at the coil. The alternator would be negative grounded to the frame. I'm an electrical novice at best, but my thought was that a 10Si alternator from the late 60s/early 70s generally would work.

 

[flyweight]

Negative Ground System is as shown below.
Negative(-) Terminal of coil is run to Point/Condenser.

Positive Ground System will be revered. Positive(+) Terminal of coil is run to Points/Condenser..