The Ford Barn

Nick in Fayetteville · 02-23-2015, 07:59 PM

Why would it matter which side of the coil ( 6 volt) that you ran your red wire from igniton switch to? Mine has been on the passenger side for years. The books say run it to the drivers side of the coil with positive side being on the right. A coil is a coil....Why would it matter as long as a circuit was being completed?

Joe K · 02-23-2015, 08:05 PM

I think the only reason it is run the way it is is so that the ignition current doesn't have to flow through the meter. Only your "accessories" (lights, sundries, things you have control over) get put through the ammeter.

And perhaps this to give you a heads up in "balancing" current inflow versus current outflow to your battery?

It used to be a lot of Model A were driven during the day with the headlights on - trying not to upset that "balance."

Gosh. Voltage regulators make life SO much simpler.

Joe K

edmondclinton · 02-23-2015, 08:17 PM

Quote:

Originally Posted by Nick in Fayetteville

Why would it matter which side of the coil ( 6 volt) that you ran your red wire from igniton switch to? Mine has been on the passenger side for years. The books say run it to the drivers side of the coil with positive side being on the right. A coil is a coil....Why would it matter as long as a circuit was being completed?

Go to and read the following:

http://mgaguru.com/mgtech/ignition/ig104.htm

Tom Wesenberg · 02-23-2015, 08:17 PM

This tells the whole story, and only takes minutes to read.

http://www.chicagolandmgclub.com/tec...neral/574.html

zzlegend · 02-23-2015, 08:28 PM

I took Toms advise a couple of years ago, I bought one of these and use it quite frequently. Purchased from Brattons.

Search Results > IGNITION SPARK AND COIL TESTER

This device uniquely shows ignition spark presence and coil polarity while engine is cranking or running. This thumb sized tool is placed between the ignition coil and distributor. It shows by high intensity flashing lights that: (Spark is present - Spark is not present - Polarity is “right” - Polarity is reversed.) The Sparklite works with ALL types of spark ignition systems: points, transistor.. It indicates properly with 6, 12, volt, positive or negative battery systems. Instructions for use are included.. Genuine NU-REX Made by Nu-Rex.

Part #17140

Mitch//pa · 02-23-2015, 08:46 PM

Sponsored Links (Register now to hide all advertisements)

[QUOTE=zzlegend;1039235]I took Toms advise a couple of years ago, I bought one of these and use it quite frequently. Purchased from Brattons/QUOTE]

i have one also

Chris Haynes · 02-23-2015, 09:01 PM

Without buying an expensive tool you can check which way your spark is traveling by holding the tip of a pencil between the plug wire and spark plug. The electricity takes a bit of the pencil with it and makes it easy to see.

edmondclinton · 02-23-2015, 10:03 PM

Quote:

Originally Posted by Chris Haynes

Without buying an expensive tool you can check which way your spark is traveling by holding the tip of a pencil between the plug wire and spark plug. The electricity takes a bit of the pencil with it and makes it easy to see.

Yup, pencil is all you need...

MrBruce · 02-24-2015, 09:08 AM

Ditto, works great and it's a quick check. Use it every spring at our tune up.

EZLIFE · 03-12-2023, 12:31 PM

Which way is the pencil lead supposed to travel?

nkaminar · 03-12-2023, 03:20 PM

All above is correct and important but does not answer how the coil is hooked to the ammeter. During the production of the Model A the wiring was changed so that the coil was hooked to the opposite side of the ammeter than the battery so that the ammeter would register current used by the ignition system. When you turn the ignition switch on, and with the points closed, the ammeter should show a discharge. Don't leave the ignition on very long without running the engine because there is a chance of burning out the coil or points. If the ammeter does not show a discharge, switch the side of the distribution block that the coil is hooked to, or the ignition switch is hooked to if a modern ignition switch is used with modern wiring. That way the ammeter will be telling the complete story.

rotorwrench · 03-12-2023, 03:46 PM

The pencil test produces a flare when the graphite rich pencil lead it placed in the path of a high tension spark. The high tension voltage will use the graphite as a conductor in it's leap toward the ground. It's sometimes hard to see the flare and which way it goes. If the flare jumps toward the ground then the polarity is correct. If it appears to jump back toward the coil lead then the polarity is wrong.

Older coils may be marked DIS on one terminal and BAT on the other but modern types are pretty much all marked with a - (minus sign) or a + (plus sign). Considering where some coils are manufactured, there is a possibility that the polarity signs are wrong.

I use the NU-Rex polarity test tool since it plugs in the high tension terminals between the coil and the distributor. A person can see that better and it has the added use of checking for spark when troubleshooting.

Don't be afraid to start a new post. This one is pretty old.

Big hammer · 03-12-2023, 03:51 PM

Use a heavy glove when you hold the pencil, I was the lease path to ground when I tried this method

ModelA29 · 03-12-2023, 04:25 PM

Quote:

Originally Posted by Big hammer

Use a heavy glove when you hold the pencil, I was the lease path to ground when I tried this method

Awww you ruined the fun

burner31 · 03-12-2023, 06:49 PM

Quote:

Originally Posted by ModelA29

Awww you ruined the fun

The spark of life.

shew01 · 03-13-2023, 03:32 PM

Quote:

Originally Posted by Big hammer

Use a heavy glove when you hold the pencil, I was the lease path to ground when I tried this method

I was wondering when someone would mention this possibility. Sorry you got buzzed…

Sent from my iPhone using Tapatalk

rotorwrench · 03-13-2023, 05:23 PM

That's why I use the Sparklite tester. The spark will find whatever ground may be there. We are as good a ground as any. Plus, I don't see as well as I used to and getting too close is not a good option.

29spcoupe · 03-13-2023, 06:03 PM

What about metal migration at the points?

nkaminar · 03-14-2023, 06:25 AM

If the coil and condenser are matched correctly there is no metal migration at the points. The coil and condenser are a tuned LC circuit. The opening of the points initiates a ringing between the coil and condenser that causes the initial spark and several following sparks in rapid sequence. Once the points are open there should be no sparking there. However, this ideal situation is not the actual case in most ignition systems and there will be some metal migration. The solution is regular dressing of the points. The coil polarity will not effect this as the voltage across the point is not changed by wiring the coil differently.

02-23-2015, 08:05 PM	#2
Joe K Senior Member Join Date: Jul 2010 Location: Cow Hampshire Posts: 4,188	Re: Why would it matter? I think the only reason it is run the way it is is so that the ignition current doesn't have to flow through the meter. Only your "accessories" (lights, sundries, things you have control over) get put through the ammeter. And perhaps this to give you a heads up in "balancing" current inflow versus current outflow to your battery? It used to be a lot of Model A were driven during the day with the headlights on - trying not to upset that "balance." Gosh. Voltage regulators make life SO much simpler. Joe K __________________ Shudda kept the horse.

02-23-2015, 08:17 PM	#4
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: Why would it matter? This tells the whole story, and only takes minutes to read. http://www.chicagolandmgclub.com/tec...neral/574.html

02-23-2015, 08:28 PM	#5
zzlegend Senior Member Join Date: May 2010 Location: Reseda, Calif. Posts: 2,188	Re: Why would it matter? I took Toms advise a couple of years ago, I bought one of these and use it quite frequently. Purchased from Brattons. Search Results > IGNITION SPARK AND COIL TESTER This device uniquely shows ignition spark presence and coil polarity while engine is cranking or running. This thumb sized tool is placed between the ignition coil and distributor. It shows by high intensity flashing lights that: (Spark is present - Spark is not present - Polarity is “right” - Polarity is reversed.) The Sparklite works with ALL types of spark ignition systems: points, transistor.. It indicates properly with 6, 12, volt, positive or negative battery systems. Instructions for use are included.. Genuine NU-REX Made by Nu-Rex. Part #17140

02-23-2015, 08:46 PM	#6
Mitch//pa BANNED Join Date: May 2010 Location: Bucks County, PA Posts: 11,454	Re: Why would it matter? Sponsored Links (Register now to hide all advertisements) [QUOTE=zzlegend;1039235]I took Toms advise a couple of years ago, I bought one of these and use it quite frequently. Purchased from Brattons/QUOTE] i have one also

02-23-2015, 09:01 PM	#7
Chris Haynes Senior Member Join Date: May 2010 Location: Camarillo, CA and Pine Grove, CA Posts: 2,841	Re: Why would it matter? Without buying an expensive tool you can check which way your spark is traveling by holding the tip of a pencil between the plug wire and spark plug. The electricity takes a bit of the pencil with it and makes it easy to see. __________________ 1921 Runabout 1930 Tudor Early 1930 AA Speed costs money. How fast do you want to go?

02-23-2015, 07:59 PM	#1
Nick in Fayetteville Senior Member Join Date: May 2010 Location: Fayetteville, NC Posts: 341	Why would it matter? Why would it matter which side of the coil ( 6 volt) that you ran your red wire from igniton switch to? Mine has been on the passenger side for years. The books say run it to the drivers side of the coil with positive side being on the right. A coil is a coil....Why would it matter as long as a circuit was being completed?

02-24-2015, 09:08 AM	#9
MrBruce Senior Member Join Date: Oct 2014 Location: Charlotte, NC Posts: 311	Re: Why would it matter? Ditto, works great and it's a quick check. Use it every spring at our tune up.

03-12-2023, 12:31 PM	#10
EZLIFE Member Join Date: Dec 2021 Posts: 33	Re: Why would it matter? Which way is the pencil lead supposed to travel?

03-12-2023, 03:20 PM	#11
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,950	Re: Why would it matter? All above is correct and important but does not answer how the coil is hooked to the ammeter. During the production of the Model A the wiring was changed so that the coil was hooked to the opposite side of the ammeter than the battery so that the ammeter would register current used by the ignition system. When you turn the ignition switch on, and with the points closed, the ammeter should show a discharge. Don't leave the ignition on very long without running the engine because there is a chance of burning out the coil or points. If the ammeter does not show a discharge, switch the side of the distribution block that the coil is hooked to, or the ignition switch is hooked to if a modern ignition switch is used with modern wiring. That way the ammeter will be telling the complete story. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. Last edited by nkaminar; 03-12-2023 at 03:26 PM.

03-12-2023, 03:46 PM	#12
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,468	Re: Why would it matter? The pencil test produces a flare when the graphite rich pencil lead it placed in the path of a high tension spark. The high tension voltage will use the graphite as a conductor in it's leap toward the ground. It's sometimes hard to see the flare and which way it goes. If the flare jumps toward the ground then the polarity is correct. If it appears to jump back toward the coil lead then the polarity is wrong. Older coils may be marked DIS on one terminal and BAT on the other but modern types are pretty much all marked with a - (minus sign) or a + (plus sign). Considering where some coils are manufactured, there is a possibility that the polarity signs are wrong. I use the NU-Rex polarity test tool since it plugs in the high tension terminals between the coil and the distributor. A person can see that better and it has the added use of checking for spark when troubleshooting. Don't be afraid to start a new post. This one is pretty old.

03-12-2023, 03:51 PM	#13
Big hammer Senior Member Join Date: Jun 2014 Location: Land of Lincoln Posts: 3,138	Re: Why would it matter? Use a heavy glove when you hold the pencil, I was the lease path to ground when I tried this method __________________ Don't force it with a little hammer tap, tap, tap get a bigger hammer tap done

03-13-2023, 05:23 PM	#17
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,468	Re: Why would it matter? That's why I use the Sparklite tester. The spark will find whatever ground may be there. We are as good a ground as any. Plus, I don't see as well as I used to and getting too close is not a good option.

03-13-2023, 06:03 PM	#18
29spcoupe Senior Member Join Date: Aug 2014 Location: Rhinebeck, NY Posts: 763	Re: Why would it matter? What about metal migration at the points?

03-14-2023, 06:25 AM	#19
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,950	Re: Why would it matter? If the coil and condenser are matched correctly there is no metal migration at the points. The coil and condenser are a tuned LC circuit. The opening of the points initiates a ringing between the coil and condenser that causes the initial spark and several following sparks in rapid sequence. Once the points are open there should be no sparking there. However, this ideal situation is not the actual case in most ignition systems and there will be some metal migration. The solution is regular dressing of the points. The coil polarity will not effect this as the voltage across the point is not changed by wiring the coil differently. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.