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Robert Buchanan

D24 ignition coil ohms

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Thanks very much.  Reading less than 4 on the high side.  Replaced with a new 6 volt coil but might have the positive/negative wires switched on the coil.  Does the black wire from the distributor go to the positive or negative post on the coil?

 

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1 hour ago, Robert Buchanan said:

Does the black wire from the distributor go to the positive or negative post on the coil?

On positive grounded car the wire to the distributor in wire  should go to the positive marked terminal on the coil.

 

DJ

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1 hour ago, Robert Buchanan said:

Black wire from distributor goess to positive terminal on coil

Yes as long as your car is still positive grounded system. (i.e. not changed from stock setup).

 

You will get this working, patience seems to help me, a cold --- break seems to help the thought  processes!

 

DJ

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Update.  I cleaned the point contacts and the black wire from the dist to positive side of coil.  POints open with rotor and cap on i get 1.6 across the neg and pos lugs on the coil.

Points closed i get nothing.

 

I also ran  a few other tests.  Points open ground to pos side of battery I get .4 on stationary side of points an 0 on moveable side of points.  I also get .4 on the screw that locks the points in, and .4 on several other screws within the dist.  I get 0 on the black wire at the dist.

 

Pardon my ignorance, it's my parents fault.

 

Can anyone be more specific on the testing process?

Ignition on or off?

Rotor and distributor on or off?

Where do I place the meter leads for testing open and closed?

Appreciate any advice.

Edited by Robert Buchanan
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   Here’s an excerpt from an article that I saved about this very issue, (since our car was/is wired as 6v-neg ground) that explains the “why’s and wherefore’s”:

   The ignition coil’s essentially a low-voltage to high-voltage transformer with about 100-to-1 ratio of windings and voltage. The coil case isn’t grounded, and both primary and secondary windings inside are "floating", or isolated from the case. The only thing the windings have in common is one end connected to the same primary terminal, and it really doesn't matter much which one. Being a transformer, it must have pulsating, ie: alternating, current to work. Initial pulsating is done by connecting and disconnecting the primary circuit ground connection. Alternating current then comes into the function in a big way by electrical "ringing" in the condenser at very high frequency. A transformer isn’t affected by polarity, since it’s an alternating current device, so it matters not to the transformer what the input or output polarity may be. Any polarity on the primary side, and any polarity on high tension side, will produce the same quality of spark.

   Why, then, do we worry about coil polarity? Because the spark plugs do care which way the electrons are flowing in the high tension circuit. The spark plug has a thermally insulated center electrode (surrounded by ceramic). With the engine running, the center electrode runs substantially hotter than the exposed end electrode. Design of the ceramic insulator determines how hot the center electrode will run, leading to the designation of hotter or colder spark plugs. As electrons go, they love to jump away from a hot surface, and fly toward a colder surface, so it’s easier to drive them from hot to cold rather than from cold to hot. The end result is a difference of 15-30% in voltage required to make the spark "initially" jump the gap on the plug, depending on which way it’s going. So the spark plug prefers to see a voltage potential that’s negative on the center electrode, and positive on the end electrode, for the very first hop of the spark. Oddly enough, this has nothing to do with polarity of the vehicle electrical system, but it’s influenced by the common connection inside the ignition coil.

   The common knowledge about electrons is that they carry a negative charge. For electrical bits (similar to magnetic bits), opposites attract each other, and negatives repel one another. This means that the direction of flow of electrons in a car is from the battery’s negative post through the wiring to the battery’s positive post (not necessarily intuitive). If you reverse cable connections on the battery, the current flows in the opposite direction through the vehicle wiring. For most original functions on an older car, this matters not one whit to anything, as most original equipment on most older cars isn’t polarity sensitive (except maybe the optional radio). As one end of the primary winding in the ignition coil’s connected to one end of the secondary winding, reversing polarity of the coil primary side will reverse the drive direction of the spark current on the output side (even though current in the vehicle low-voltage wiring still flows the same way).

   So, reversing vehicle electrical system polarity will reverse direction of the spark drive. The engine still runs either way, but spark might be more reliable under marginal conditions if you get it right. The simple fix for this is to reverse the two primary wire connections on the ignition coil. Because the output spark’s very much higher voltage (20,000v) than the car battery (12v), it doesn't care if the battery polarity’s helping or hindering by a meager 12-14 volts in battery potential.

SUMMARY: You only need to match the terminal markings to the battery posts. For positive ground, the "+" terminal goes to the distributor (to be grounded on the engine block). For negative ground, the "-" terminal goes to the distributor (to be grounded on the engine block).

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