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Old 03-22-2019, 02:57 PM   #1
37 Coupe
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Default Coil + or -

I have an old Bosch coil on my Model a '31 that I know works so I planned on reusing it.Today I finally got around to reinstalling the popout switch and new wiring.Problem is on double checking my coil ,wiring schematic and Les Andrews book I notice the coil does not show which post is positive and negative,no + or - nothing. So should I go ahead and buy a coil that is probably going to be China made or this: does it matter which post or terminal I declare positive if I put correct connections on one side and correct on opposite side? Or like I said by a new coil? I also installed the NuRex temperature gauge on the bottom of the gauge panel with the mounting fixture that fits in two bottom holes and gauge is loose in the bracket.What needs to be done tape gauge body to make a fit? Just seems like evry step is an issue nothing ever easy.
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Old 03-22-2019, 03:28 PM   #2
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Default Re: Coil + or -

Even the original coils usually don't have marking. Simple way around is get the ignition polarity indicator tool that everyone sells. Start the engine, look at the light and you have the answer.
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Old 03-22-2019, 03:44 PM   #3
denniskliesen
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Default Re: Coil + or -

This is what 100IH is talking about. Read page 390 in the Service Bulletins. Ford changed the wires which placed the ammeter in the ignition circuit. Just to not confuse the Nu Rex polarity tester takes the guess work out of it. You can also hold the tip of a pencil between the spark plug wire and the sparkplug to see which side of the pencil the spark occurs.
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Old 03-22-2019, 05:40 PM   #4
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Default Re: Coil + or -

Bosch? good coil,if it has a number 15 on one of the tabs thats the hot side.
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Old 03-22-2019, 06:35 PM   #5
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Default Re: Coil + or -

Quote:
Originally Posted by Railcarmover View Post
Bosch? good coil,if it has a number 15 on one of the tabs thats the hot side.
How do you define "hot" - positive or negative?

Um, Dennis, pencils are SHOCKINGLY cheaper!
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Old 03-22-2019, 06:55 PM   #6
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Default Re: Coil + or -

It will run either way hooked up. But use the tool,,,,it wont lie.
In my opinion, pencils suck. Dennis has it right. I have 2 of those in my tool boxes'
Just remember,,,,,you can lead a horse to water,,,,,but a pencil must be lead,,,,,,
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Old 03-22-2019, 07:00 PM   #7
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Originally Posted by zzlegend View Post
It will run either way hooked up. But use the tool,,,,it wont lie.
In my opinion, pencils suck. Dennis has it right. I have 2 of those in my tool boxes'
Just remember,,,,,you can lead a horse to water,,,,,but a pencil must be lead,,,,,,
I want to add to your comment: It will run if connected the wrong way, just not as good.

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Old 03-22-2019, 07:02 PM   #8
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Default Re: Coil + or -

If it's Bosch it was probably stolen from a VW. And like Railcarmover says 15 goes to the points. With a generator electricity moves from + to - to get to ground which the points are just that.
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Old 03-22-2019, 07:04 PM   #9
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Default Re: Coil + or -

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If it's Bosch it was probably stolen from a VW. And like Railcarmover says 15 goes to the points. With a generator electricity moves from + to - to get to ground which the points are just that.
It is marked American Bosch.
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Old 03-22-2019, 07:09 PM   #10
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Default Re: Coil + or -

Quote:
Originally Posted by Charlie Stephens View Post
I want to add to your comment: It will run if connected the wrong way, just not as good.

Charlie Stephens
Yes Charlie. I should have stated that. Thanks.
As for those Bosch coils, i am running two of those on my roadsters. Great coils.
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Old 03-22-2019, 07:33 PM   #11
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Default Re: Coil + or -

You can lead a horse to drink but you can't make him water?
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Old 03-22-2019, 07:43 PM   #12
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you can lead a horse to drink but you can't make him water?
:d:d:d:d:d:d:d:d
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Old 03-22-2019, 09:34 PM   #13
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Default Re: Coil + or -

The pencil trick has been around for ages. High school auto shop teachers loved to demonstrate this to the class, then hand the pencil to the class comedian and have him try it.


Years ago when the tool came on the market I bought one and one day at a club event we checked about 20 cars and found about half were backwards. The owners hadn't noticed the difference.


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Old 03-22-2019, 11:10 PM   #14
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Default Re: Coil + or -



the best inverted 12v coil known to man..see the 15? thats where the hot wire goes,other side goes to the points..
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Old 03-23-2019, 04:48 AM   #15
johnbuckley
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Default Re: Coil + or -

Quote:
Originally Posted by Tom Endy View Post
Years ago when the tool came on the market I bought one and one day at a club event we checked about 20 cars and found about half were backwards. The owners hadn't noticed the difference.
Tom Endy
Out of interest Tom ,Did they notice any improvement once connected correctly?
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Old 03-23-2019, 05:15 AM   #16
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Default Re: Coil + or -

Pencil details:

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


Although, if the MG boys are referring to Lucas, caveat emptor!!
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Old 03-23-2019, 09:41 AM   #17
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Default Re: Coil + or -

Quote:
Originally Posted by Bruce of MN View Post
Pencil details:

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


Although, if the MG boys are referring to Lucas, caveat emptor!!
Lucas,the Prince of Darkness..had a Triumph Trophy,at night you could light a smoke off the zener diode.On the other hand,German Bosch makes superior components,if youre not into fine point their coil cant be beat,was engineered to run inverted too..
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Old 03-23-2019, 10:11 AM   #18
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Default Re: Coil + or -

Posted in error. My bad.
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Old 03-23-2019, 10:13 AM   #19
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Default Re: Coil + or -

Quote:
Originally Posted by Railcarmover View Post


the best inverted 12v coil known to man..see the 15? thats where the hot wire goes,other side goes to the points..
I didn't realize that you meant a much newer coil for the #15.This is the American Bosch coil I already had on the firewall and it did run on this. I running new wires and just questioned the previous hookup.
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Old 03-23-2019, 10:38 AM   #20
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Default Re: Coil + or -

Electrons move from - to +. Electricity does not flow only electrons. Voltage is the force that drives the electrons. Amp meters measure the amount of electrons that flow past a point.
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