Reversed battery polarity on 8N

[Soundguy]

... Someone once told me that the only thing on the engine that care was the solenoid....

And they weren't familiar with fords either.

solenoid don't care 6v or 12v, positive or negative ground...

it's just an electromagnet... and 6v wiring was made heavier duty than 12v wireing for current capacity... and wire insulation that is ok for 6v should still be way fine for 12v...

soundguy

 

[Lil_FarmerJim]

Jim.. it's apparrent your not familiarwith ford electrics.

Too true, just offering info/opinion.

our old starter motors spin the same direction no matter what polarity.. it's because the way the field is wired.

You're going to have to explain that one to me, is it A/C? I've not encountered a D/C motor that will spin the same direction with reversed polarity

same with the ignition coil.. it will spark either polarity.. ( though best to run at correct polarity for optimum spark )

I was always told it wouldn't work at all in reverse, too much resistance or something. New one for me. (always happy to learn)

old n's had no alternator.. only a generator.. and they can run either polarity once polarized correctly.

Keyword there is polarized correctly. Other wise it would be a direct short, would it not?

 

[Bird]

And they weren't familiar with fords either.

solenoid don't care 6v or 12v, positive or negative ground...

it's just an electromagnet... and 6v wiring was made heavier duty than 12v wireing for current capacity... and wire insulation that is ok for 6v should still be way fine for 12v...

soundguy

Maybe they're just not old enough. In late 1956 or early 1957, we had a customer (the mayor, in fact) who called one morning because his old Plymouth wouldn't start and wanted me to go put a new battery in it in his driveway, so I did. Nobody told me they had a positive ground. But fortunately, no damage at all except for a ruined battery. Of course, it had a generator instead of alternator and I'm not sure anyone had even hear of "solid state" yet.

 

[Soundguy]

You're going to have to explain that one to me, is it A/C? I've not encountered a D/C motor that will spin the same direction with reversed polarity

(dc for sure!)

series wound field...The current enters the starter, then, at the stud, splits into 2 completely separate paths.. each through a set of field coils, then though the insulated brush to the armature, and back out the armature through the 2 grounded brushed, to the metal case of the starter,

When you change the polarity both the rotor and field will change polarity so the starter spins the same direction.

if you had a permanent magnet type dc motor.. sure.. polarity change will cause direction change.... N starter has a field coil. not a permanent magnet.

I was always told it wouldn't work at all in reverse, too much resistance or something. New one for me. (always happy to learn)

In reverse, you have the primary winding in series with the secondary winding. the secondary winding is about 4Kohms.. the primary winding is about 1 ohm.. thus you have a big resistance plus a little resistance for the spark to discharge thru, vs just the large resistance. There is -some- spark potential difference.. but it is not much.. yo could tell on an engine anylizer if you had spark polarity reversed. Spark potential voltage is mainly a function of the size of the spark gap you are jumping.. a larger spark gap means more potential voltage buildup before the spark jumps the gap.. tha's why if you have a fouled plug, sometimes pulling the spark plug wire off a bit suddenly makes the cyl start fireing. they used to sell a 'spark intensifier' whch was nothing more than an extra, adjustable spark gap that you put inline with the plug. od course the ignition coil must be able to produce the extra high voltage needed.. otherwise you will just not have a spark.

Think about this.. ford 9n-2n-8n front mount distribuitor machines that have been converted from 6v positive ground to 12v negative ground are a class of machine inwhich you cannot easilly re-orient the coil to maintain correct coil polarity, as the coil is square and mounts atop the distribuitor with only the top connection available.. ie. only a single connection of the primary is available.. other side of primary hits the dish shaped points screw.. secondary tab hits the distrib cap.. when you reverse polarity.. of the battery.. you are stuck with reversed polarity on the coil.. thousands of n are runing this way. on a side mount.. you can swap coil primary connections side to side.. etc.

if you had an electronic module running yor ignition.. then yeah.. won't work on reverse polarity from what it was designed for.

Keyword there is polarized correctly. Other wise it would be a direct short, would it not?

nope.. polarizing a generator just establishes a base magnetic field in it's field pieces.. that way when the armature starts rotating there is residual magnetics to start bootstrapping voltage up.. once voltage comes up to threshold, cutout pulls in and battery starts charging. during this time, depending on field circuit type, field current will being generated to supplement residual magnetics.. etc. thus properly polerizing a genny ensure that it will charge when it starts spinning, and that charge polarity equals bat polarity.. this makes the regulator happy.. otherwise the contacts in the reg can be welded as the genny could be charging opposite of the battery ( worse than a short actually.. it's a addative issue with bat volts , 0 and genny volts ).

soundguy

 

[kebo]

And they weren't familiar with fords either.

solenoid don't care 6v or 12v, positive or negative ground...

it's just an electromagnet... and 6v wiring was made heavier duty than 12v wireing for current capacity... and wire insulation that is ok for 6v should still be way fine for 12v...

soundguy

A 12V solenoid WILL care if you put it in a 6V system! It will be getting half the voltage it needs to energize so it might kick in hard, or it might not? Have you had personal experience doing that cause I'm curious to know if it would energize well enough to crank up the tractor?

 

[Soundguy]

A 12V solenoid WILL care if you put it in a 6V system! It will be getting half the voltage it needs to energize so it might kick in hard, or it might not? Have you had personal experience doing that cause I'm curious to know if it would energize well enough to crank up the tractor?

Go back and re-read my post. I'm SPECIFICALLY referring to his oem 6v ford solenoid.. ( my reply was to dougster's post #9.. in it he was talking about a ford 8n, and mentioned that someone told him that that solenoid wouldn't do reverse polarity.. I told him they were mistaken )...and they DO IN FACT run fine on 12v.. +/- ground. that's why i said they don't care 6v or 12v, positive or negative ground.... we aren't talking about every solenoid ever made in the world.. just the one that came on those ford tractors that dougster was talking about!! Did you not read any of the previous posts and instead just hoped in on the last post to dispute my reply out of context????

Kick in hard? ( do you even know how a ford 8n starter works???????? have you ever seen one or worked on one???? ) remember.. the ford solenoid that we are talking about is just a 3 terminal electric switch that sets on the side of the 8n starter held on by 2 small screws. battery on one side.. starter on the other, isolated base, and a small 3rd side wire fron the tranny top safety interlock GROUNDING switch..... it is not a drive gear engagement. The bendix/drive gear on that model is mounted to the end of the starter shaft, and sucks 'IN' to engage the -back- (trans side) of the flywheel.. once the engine is started, the flywheel overspeeds the drive gear and unlocks the dogs holding it engaged and spins it back out to the end of the starter shaft... this isn't like a modern starter that the solenoid kicks the drive gear out for starting and it engages the engine side of the flywheel.

soundguy

 

[jinman]

Soundguy, you are doing a great job of explaining this. . . maybe even a better job of keepin' your cool when challenged. Superb job! You've given accurate and detailed info. Now, I hope the OP will just check his alternator and solid state VR if he has them. Those are the things I think may be "toasty."

 

[Soundguy]

I agree... that alt should be taken to a napa or autozone.. or other store that does free checks.. i'd be surprised if there isn't some damage to either the vreg module or the trio/output rectifiers.

soundguy

 

[kleake]

Not to bring back an old thread, but I wanted to add a little of my own experience to this and show that things do work in ways you don't think they would sometimes.

Background: I just aquired my grandfathers old 49 8N that he has had since the early 50's. It was used on a regular basis and has only sat for about 2 years as it had several times before. About 5 years ago it had the top end rebuilt, and a new starter put on, which is a 12v starter as we had plans to convert it to a 12v system, but all other parts were still original.

We charged it over night, cleaned up the carb and fuel lines and tried to fire her up by pulling it since the battery didn't seem to have enough juice and that's how we would always do it if she had set for a period of time before. She did spit and sputter and would run under full throttle, but just barely... We had the battery on the charger overnight, but thought we would check the voltage,,,,,, 2 volts.... We figured the generator was having a hard time overcoming that, so off to the store for a new battery. My son took the battery out, so when I went to put the new one back in, the battery terminals didn't fit right, but I've seen that before with old terminals, so I didn't think much of it (not realizing this was to be positive ground). We pulled her again and she fired up and ran pretty decent, but wasn't hitting on all cylinders. Pulled the plugs, cleaned them up and got her running pretty decent. Put probably an hour run time on her and put her up for the night. The next morning, she would only hit on a couple of cylinders but never actually start. The plugs were wet, so I figured they are fouled and such, and new ones would be best. After new plugs, she fired right up and ran quite good. I decided to check the battery and found it wasn't charging and it was getting low, so I started tinkering and that's when I realized this tractor is supposed to be positive ground!!!

I immediately swapped the battery back to positive ground as it should be and she started right back up, but still no charge. I tried to polerize the generator, but couldn't read the terminal on the regulater as it is the original as well, and was pretty dirty. So, instead I just pulled the cover off the regulater, and to my surprise the inside of that thing was spic and span clean! :thumbsup: While she was running, I manually closed one of the relays and got a small spark, but she was then charging. I shut her down and started her back up a couple of times and all appeared to be good, so I buttoned her up and went to work box blading my driveway.

In the end, the coil, lights, and starter worked in reverse polarity,,, even this newer 12V starter. Seems odd I know,,,, but I sure learned alot, and I do electronics for a living as well! These old tractors are definitely bulletproof!

 

[Soundguy]

shouldn't be odd if you do electronics for a living.

you likely closed the cutout, which polerized the genny..

no need to read the reg to polerize an a circuit system.. just jump bat to armature and go.

easy to tell what circuit type if you don't know by looking at the vreg field control, since it connects the field coil to ground via a vibrating contact.. has a bias resistor from fld to grns onthe bottom of the reg too.

soundguy

soundguy