+ & - side of coil?

R

Relvis P. Johnson

Member
Switching from Nu-rex back to standard Distributor, the points ground out when closed. Do I switch the coil wires? Will that burn out another new ammeter?
 
You really should start with a schematic. Without one, you're just guessing. Notice that the points are supposed to short to ground. That completes the circuit through the ignition switch, which energizes the coil. Tracing this circuit can answer a lot of questions.

I printed this out and laminated it. It's in my car at all times.

Hope it helps!



Wiring-DiagramColor2sm_zps8919c530.jpg
 
Relvis P. Johnson said:
Switching from Nu-rex back to standard Distributor, the points ground out when closed. Do I switch the coil wires? Will that burn out another new ammeter?
Click to expand...

Yes the point will ground out if the system is working normal.

Follow the wiring, If the car ground is pos then the pos on the coil goes to the points. If the cars ground is neg the neg goes to the points.

Click here for schematic

Put a fuse or circuit breaker in and you will never blow an ammeter again.

The fuse holders sold in the past 4,5 years are miles above the ones sold earlier as far as durability, notice the plate the battery connection is mounted on.

img_Large.asp
 
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Question regarding 1930 wiring change to include the ignition circuit thru the amp meter. Do you just. Move the black wire from the yellow side of the junction box, to the yellow/black side, which now puts it on the output side of the amp meter? If so, then the laminated wiring diagram from mafca, is wrong, as it's note says "drivers side of COIL" that would change polarity??
 
Is the red wire in the drawing on the + or - side of the coil, or doesn't it make a difference? The drawing doesn't show. Afordman31


newshirt said:
You really should start with a schematic. Without one, you're just guessing. Notice that the points are supposed to short to ground. That completes the circuit through the ignition switch, which energizes the coil. Tracing this circuit can answer a lot of questions.

I printed this out and laminated it. It's in my car at all times.

Hope it helps!



Wiring-DiagramColor2sm_zps8919c530.jpg
Click to expand...
 
Chuck Sea/Tac said:
Question regarding 1930 wiring change to include the ignition circuit thru the amp meter. Do you just. Move the black wire from the yellow side of the junction box, to the yellow/black side, which now puts it on the output side of the amp meter? If so, then the laminated wiring diagram from mafca, is wrong, as it's note says "drivers side of COIL" that would change polarity??
Click to expand...

At the end of 1929 the coil feed wire (black) was moved to the other side in order to show coil current while cranking the engine. BUT, at the side time the coil primary terminals switch sides in reguard to polarity. There is a picture and description in the service bulletins.

I moved my black wire to the other terminal box post on my 1928 in order to see the coil draw while cranking. It's always best to do a coil polarity check to be sure.

The Chicagoland MG club has an excellent short read on coil polarity and is easily found by doing a Google search for "coil polarity".
 
If you blow up the view of the coil in the wiring diagram shown above, you can get a glimpse of how the physics of what's going on in the coil works. Most important, notice that the secondary (fine) winding is connected on the positive or ground side of the coil primary winding. This ultimately assures that the electron flow in the secondary winding sends electrons TO the spark plugs, which is what drives correct coil polarity connection. Electrons find it easier to jump (i.e., create a spark) from a hotter metal surface--the insulated spark plug tip is always hotter than the threaded base screwed into the water-cooled head.

Picture the electrons moving. Electron flow in the diagram is from the negative battery terminal through the ammeter, through the coil primary, through the ignition switch, then on to the points and on to ground and back to the battery. Thus, you might think that to feed electrons TO the spark plug tips, it would be better to feed electrons most directly into the secondary coil winding by connecting it to the negative side of the primary coil terminal. However, the opposite is true because the current induced in the secondary winding goes in the opposite direction than in the primary.
 
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Tom Wesenberg said:
At the end of 1929 the coil feed wire (black) was moved to the other side in order to show coil current while cranking the engine. BUT, at the side time the coil primary terminals switch sides in reguard to polarity. There is a picture and description in the service bulletins.

I moved my black wire to the other terminal box post on my 1928 in order to see the coil draw while cranking. It's always best to do a coil polarity check to be sure.

The Chicagoland MG club has an excellent short read on coil polarity and is easily found by doing a Google search for "coil polarity".
Click to expand...

So are you saying the original coil polarity was wrong.?
 
Chuck Sea/Tac said:
So are you saying the original coil polarity was wrong.?
Click to expand...

No coil is built with wrong polarity. It is what it is, and polarity is determined by how you connect the two wires. It's nice when the terminals are marked + and -, but some coils are marked "bat" and "dist", which is useless unless you know what car that coil was for. Coil polarity is determined by which battery post goes to ground and which coil terminal goes to the points. If the battery is + ground, then you want the + on the coil going to the points, which is the ground path for the coil.

Any coil marked with "bat" and "dist" needs to have the polarity tested as described by the Chicagoland MG club posting.
 
Tom, what I meant is: was the early wiring to the coil wrong causing reverse polarity?as mentioned earlier, and from the picture/description in the service bulletins, the coil wires are reversed, as well as the black wire moved to the other side of the terminal box, Or at least that's what I'm seeing.
 
The coil polarity and ammeter polarity are two entirely separate issues. Switching the black wire on your car from one JUNCTION BOX lug to the other has nothing to do with the coil polarity wiring. Coil polarity is determined by wires connected to the posts on the COIL. The junction box switcheroo merely puts the ammeter in or out of the ignition circuit.
 
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Tom Wesenberg said:
At the end of 1929 the coil feed wire (black) was moved to the other side in order to show coil current while cranking the engine. BUT, at the side time the coil primary terminals switch sides in reguard to polarity. There is a picture and description in the service bulletins.

I moved my black wire to the other terminal box post on my 1928 in order to see the coil draw while cranking. It's always best to do a coil polarity check to be sure.

The Chicagoland MG club has an excellent short read on coil polarity and is easily found by doing a Google search for "coil polarity".
Click to expand...

Chuck Sea/Tac said:
Steve: if you read toms post #9, he is moving both coil wires and the black to the other side of the junction box.
Click to expand...

I be bumfuzzled!
 
Check the SERVICE BULLETINS for the end of 1929 and you will see Ford moved the black wire on the coil because Ford started building the STRAIGHT POLE coil, and dropped the SLANT POLE coil, and the new straight pole coil had the primary terminals polarity reversed from the slant pole coil.

Ford also wanted the coil draw to show on the ammeter, so they move the feed wire to the other terminal box post.

There is a very rare exception to the coil polarity, as the coil terminals polarity must have happened a day or two before the straight pole coil was introduced. I do have one slant pole coil with a date code for late 1929 and it has the terminal polarity reversed from the norm for slant pole coils.
 
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