Ignition Coil and Points Polarity 101

[John T]

I saw some confusion below regarding if Ignition Coils are Polarity Sensitive and if standard Ignition Points are Polarity Sensitive, so as a public service to my great bunch of fellow YT ers, I will provide an electrical engineers "OPINION" and perspective which will hopefully help out. NOTE THIS IS MY OPINION, OTHERS ARE ENTITLED TO THEIR OWN DIFFERENT OPINIONS (but NOT their own facts lol)


1) IGNITION COIL POLARITY There is indeed a reason why ignition coils have their small + and - terminals labeled as such, if it made no difference why label them at all. The reason is its easier to emit electrons from a HOTTER to a relatively COLDER surface (thermionic emission I believe its called) and that's why in a vacuum tube there's a heater located under the Cathode from which electrons flow up to the Plate.

BUT DONT TAKE MY WORD FOR IT IF YOU READ THE ARTICLES BELOW THEY EXPLAIN IT IN GREATER DETAIL

http://www.chicagolandmgclub.com/techtips/general/574.html

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


2) IGNITION POINTS POLARITY

In like 55 years of buying hundreds of sets of ignition points (I was a used tractor dealer and farmer) when I went to
a tractor dealer or NAPA etc to buy a set I WAS NEVER ASKED IF IT WAS A POS OR NEG GROUNDED TRACTOR.

In like 55 years of buying hundreds of sets of ignition points I NEVER SAW ON THE BOX FOR POS OR NEG GROUND

THE REASON BEING """""IN MY OPINION""""" IGNITION POINTS ARE NOTTTTTTTTTTTTTTTT POLARITY SENSITIVE. They work the same
and as well regardless if on a POS or NEG ground tractor (In my opinion that is)


3) IGNITION POINTS PITTING AND CRATERING

It was posted below there existed pictures evidencing how "points polarity" makes a difference HOWEVER the
differences is NOT due to + or - Polarity, ITS DUE TO TOO MUCH OR TOO LITTLE CAPACITANCE

SEE THE PICTURE I POSTED

4) YES Voltage Regulators ARE POLARITY SENSITIVE and the coatings and surfaces on their relay contacts makes a difference. I have seen them labeled for POS ground and I have seen them labeled for NEG ground.


I sure hope this helps and clears up the confusion. If the authors of the literature above are wrong GO TAKE IT UP WITH THEM AND FLAME ON THEM AND TELL THEM THEYYYYYYYYYYYY ARE WRONG NOT ME LOL

If others have a different "opinion" then mine or the authors above, THATS THEIR BY GOLLY RIGHT to which they are entitled and I'm NOT here to stop them even if I, an electrical engineer and past tractor dealer and farmer, disagree IVE BEEN WRONG BEFORE AND WILL BE AGAIN .............I would appreciate an in depth precise technical explanation, however if anyone thinks the above is wrong WHICH IT MAY WELL BE ?????????? But I can swear I NEVER was asked or bought points for POS or NEG ground tractors But I haven't bought all of them either lol so sure there could be a difference grrrrrrrrrrrrrrrrrr

Best wishes and God Bless and keep all here

John T BSEE, JD Retired Electrical Engineer

 

[tractorguy2]

John Deere tractors must be hard on points and condensers. I ha e a Case tractor converted to a Delco distributor. I buy a kit listed as working on JD, Allis, or Case. I replace the kit every ten to thirteen years just because I think that's when I've gotten my money's worth out of the kit.

I bought the same kit last month. I've been using for ages thinking I would replace it. The kit costs $12.99 The present kit has been in my tractor since 08. When I took the dust cover off. The points looked like brand new. I decided I would wait another two or three years.

If the kit lasts ten years in a Case tractor why won't it last that long in a John Deere?

Hooking the coil up backwards causes the spark to jump backwards in the spark plug. You can actually see the spark jumping from the block to the coil wire when checking for spark when the coil wires are reversed. This can make the tractor hard to start when the engine is fully warmed up.

 

[tractorguy2]

I thought I was replying to the JD 70 post.

 

[John T]

If you scroll through ALLLLLLLLL the tractors that single set of points will fit, I suspect some may be POS ground others NEG ground tractors HMMMMMMMMMMMMMMMMMMM if so that may tell you points are NOT polarity sensitive........

PS The points I buy from NAPA are far superior in quality then those at Tractor Supply or Rural King or Central Tractor or Orschlen

John T

 

[James Howell]

"[b:654c4848f0][i:654c4848f0]The points I buy from NAPA are far superior in quality[/i:654c4848f0][/b:654c4848f0]"

Totally agree.

 

[deeretails]

As a point of interest (maybe), when I was a wrench and tuning up vehicles (trucks, cars, tractors, whatever) if there was no metal transfer on the points I never changed the condenser. I judged the system capacitance to be balanced and that was good enough.

 

[John T]

VERY TRUE, that's an old mechanics very good way of determining a condensors proper rating. If theres no condenser at all the points will burn prematurely,,,,,,,,,,,if its too small they burn prematurely but not quite as fast,,,,,,,,,,,,if its way too big theres no spark produced at all

PLUS the pitting and cratering as the picture also explains can indicate if its too big or too small

Nice chatting with you

John T

 

[teddy52food]

Points don't last as long in a Deere because they only open for 2 cylinders instead of 4 so they are closed longer.

 

[tractorguy2]

I thought I was replying to the post about why points and condenser didn't last in the John deere 70. My first reply is on the wrong post.


I was just asking why would he be having so much trouble with his points and condenser in a John Deere? When the same set fits my Case and I've never had trouble. has to be something wrong other than his points and condenser.
This is why I was showing the backside of the package showing the listing for both Case and John Deere. I know full well points don't care if the battery is grounded positive or negative.

I have a Ford 9n, 641, 4000, plus my two Case SC's. I have used the Calco brand for ages and never had a kit yet that didn't go ten + years.I'm going to stay with my Calco brand. The NAPA store here wants $26 bucks just for the points and $22 for the condenser. I can't believe they are that much better.

 

[John T]

LOL Looks like were replying to different postings.

I was responding to a post below that indicated points are polarity sensitive I SAY NOT...........And to confirm a post about how coils WERE POLARITY SENSITIVE I SAY THATS TRUE

Oh well we still had fun and maybe some learned a thing or two hopefully

John T