Reversed coil polarity

[Mitch]

All the suppliers sell this tool for checking the coil polarity.

Yes there are other ways to accomplish this test by using a pencil, but i like tools


84BFFF9B-1099-4DCD-8069-5E8051F7AD7B.jpeg

[tbirdtbird]

I love tools, too, but I ran out of space years ago!

Did the car have symptoms?

[Mitch]

Acquiring more tools is an easy fix,, you need a bigger tool box,

[Dennis]

Easier and much faster to diagnose and fix. Takes all the guess work out. I recommend anybody that does very much Model A work to have one of these.

[Mitch]

The comments will show up in the unread topics link if you use that

[Dennis]

I never thought of that, good to know. The first drop down below FORUMS

[Mitch]

yepper

[JB-OB]

'First Rule of Tool Boxes'

How is it that the new, bigger tool box does not have enough room for all the tools from the original box ????

[Mitch]

Well Jimbo it’s all about getting the right one!

[Dennis]

Good taste there Mitch! Since I retired I need to sell off most of my tools that I will never use again. All of my Model A tools fit in a small container except for the cherry picker and engine stands.

[Mitch]

Like JImbo said, you sure don't want to be switching jobs much and having to move it.

[Tony Hillyard]

Mitch, your tool box is just un-natural! I feel uncomfortable just looking at the pictures.

[JB-OB]

Not sure I could afford the fork lift rental to move those..............

[Sunnybrook Farm]

I saw somewhere but can't remember where, that if the coil polarity is reversed there is less fire to the plugs, it will run ok but a hotter spare will be there if everything is correctly wired.

[Mitch]

I saw somewhere but can't remember where, that if the coil polarity is reversed there is less fire to the plugs, it will run ok but a hotter spare will be there if everything is correctly wired.

From my experiences it will cause more of a high speed / heavy load driveability issue

[George Miller]

plus 1

[JB-OB]

Photo #2, All that technology to adjust points and your still using a manually operated garbage pail ......

[BILL WILLIAMSON]

I just bought Cindy a voice command garbage can, cost me $230.00!
Dad Notcheap

[Tom Wesenberg]

The coil voltage remains the same, but the spark plug fires easier if the hot center electrode is negative.

My 28 coil was wire backwards, and I never noticed a thing wrong until one day when I was taking a picture to post. I noticed the wires were wrong and changed it. I'm running the original slant pole coil, which has an excellent spark.

[Dennis]

Tom, I switched my system to 12V neg ground and bought a Pertronix epoxy 3 ohm coil for 12V system. I hope it doesn't burn up my nice 3X spark plugs.

[BILL WILLIAMSON]

Doghere,
"Jist switch the coil wires, if it "BARKS" at you, switch them BACK"
Buster T.

[plyfor]

Assume you mean the red wire from the ignition switch to the negative term. on neg. grnd. set up and black hot wire from jbox battery side to coil plus side. Some folks use different wire colors. We just installed a 12 volt (-grnd.) oil filled coil that appears to be hot to the touch, more than usual. Our vendor suggesting installing it terminals up to get better secondary winding cooling, however the upper part of the coil appears to be hotter than the lower perhaps because the oil isn't full inside. Some say the epoxy coils don't dissipate heat very well but can't verify that..

[Mitch]

https://www.vintagefordforum.com/for...onversion-info

[plyfor]

We run a 5.5 head with .030-.032 plugs, .019 points for better retard, .025 rotor gap and Champion 519 (W18) plugs.The 12 v coil resistance is 4.6 ohms. We have another new Standard oil filled spare one we may try with about the same ohms. Perhaps the heat is from the engine but the coil was hotter at the top and the bracket was hot also where no oil supposedly is. Now that I think about it, the existing coil was installed by the previous owner with a Zipper ignition which we removed. Not sure that would have any impact as the engine runs perfectly and starts on 1st kick..

[2manycars]

I had a model T with battery ignition years ago, and the coil was wired backwards, and on a long ride, it overheated, the engine started missing, and it failed. I had to park the car and go get my trailer.
Tool boxes have gotten very big these days. At the local repair shop one guy has one so large I think he could attach a licence plate and a tow bar and take it down the road. Mine are the old fashioned small ones, and I still have the small 3 drawer Craftsman box I bought in 1965 for $50, full of tools.

[Mitch]

I had a model T with battery ignition years ago, and the coil was wired backwards, and on a long ride, it overheated, the engine started missing, and it failed. I had to park the car and go get my trailer.
Tool boxes have gotten very big these days. At the local repair shop one guy has one so large I think he could attach a licence plate and a tow bar and take it down the road. Mine are the old fashioned small ones, and I still have the small 3 drawer Craftsman box I bought in 1965 for $50, full of tools.

And so have the prices...

[Dennis]

Should we start a tool box thread? I haven't bought many over the years.

[Mitch]

Go ahead i would enjoy that

[BILL WILLIAMSON]

Duz the one with the BIGGEST/MOSTEST Tool Boxes WIN "something"???

[JohnnyDeMichael]

If the coil is reversed on the model A, how does that affect the running of the engine?

[Tom Wesenberg]

Unless you have a poor coil or spark plugs, you may never notice a thing. Mine was reversed for 3 years, and I only noticed it because I was taking a picture of it to post on the website. Spark plugs fire a bit easier when the polarity is correct.

[tchbil]

Its easy ......positive ground + to points ...negitive ground - to points that is the coil I am speaking about

[cpf240]

How about when the coil terminal is just labeled "dist"? Or not labeled at all?

[tchbil]

Can't see the flare? Not sure yet? You can also check spark polarity using an analog (moving needle) volt meter. Hook up a voltmeter with the negative lead to the plug terminal and the positive lead to the block. Set the meter on the highest volt range. Crank the engine over (no need to start it), and you should see an upward swing of the voltmeter needle (don't be concerned with taking a reading). If the needle swings down off the scale, your coil is hooked up wrong. To correct it reverse coil primary leads. Do not worry about the coil markings, but make note of them for future reference.

[cpf240]

My A is not running yet, and I was hoping to install the coil correctly the first time. :-)

[Mitch]

Do you have any markings on the coil that you plan to install?

[cpf240]

One coil has masking tape applied near each terminal, with a faint + or - marked on them and the word "dist" next to one terminal, a second one has "batt" next to a terminal, and a third that came from Vintique at some point does have a + and - on it. The Vintique coil measured in at 1.1 ohms, while the others were 1.4 and 1.5.

Part of my confusion is that I don't know if the coil manufacturers would mark the coil differently for positive-ground applications, or leave that up to the mechanic to 'know'.

I've read several times that some Vintique products are not the best, and with the ohm reading being a bit off, I'm planning to use the one with the tape on it.

[Mitch]

I would put the +, Batt, to the distributor for a pos ground system
The one marked "Dist" is that next to the minus symbol?

[cpf240]

Yes, the tape with the hand-written - sign is next to the terminal that is marked 'dist' on the coil.

[Mitch]

Ok
My guess is that the one marked DIST would be for a neg ground system. If I was to try that one I would hook it up with the + to the dist. Of course checking it with the polarity tool would be best to verify

[Patrick]

I too like tools. The collection keeps getting bigger and the space stays the same. Do you know how hard it is today to find center boxes, I try to buy all that I find. They are scarce.

[Mickey]

I kept having a hard time finding the socket I wanted so I decided to sort them. Found out I had four 3/8 drive - 9/16, three 3/8 - 5/8, four 1/4 drive - 3/8 and numerous duplicates. No wonder it takes me an hour to find the right one. I don't even want to look at the wrench drawer.

[JDupuis]

“Time is Money” to a tech, so they keep everything organized.

[Mickey]

No wonder I'm broke. I read a quote once that seems to fit.
"A clean desk is the sign of a sick mind."

[JDupuis]

Lol

[JohnnyDeMichael]

I tried the pencil lead test, but the arc on each side looked identical to me. I noticed on the coil the Ford emblem . . . It’s only on the front. And the mechanics handbook states which wires go on the passenger side & which go on the driver side. To do what it says, if the coil was wrong, the Ford logo on the coil would be on the backside, out of sight. Should I still get a checker and check?

[Mitch]

I would

[tbirdtbird]

try it in the dark

[JohnnyDeMichael]

Mitch, thanks!

[tchbil]

I read that polarity is important because electrons move easier from a hot surface to a cold surface. So on a spark plug the hotter part would be the center electrode and the cooler would be the ground. I also read that reversed polarity will cause as much as a 30% drop in spark voltage.

[plyfor]

All the suppliers sell this tool for checking the coil polarity.

Yes there are other ways to accomplish this test by using a pencil, but i like tools


84BFFF9B-1099-4DCD-8069-5E8051F7AD7B.jpeg

I like the little polarity checker also especially when having issues with a variety of coils. On ours, one would think the light would be green to indicate OK, rather than red.

[CSPIDY]

Mechanic is only as good as his tool