Accidentally pulled Alt Blue Field Wire

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Robj

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Redding, California
70 Dart 318

Well, I guess I screwed up. The engine was running and I was rearranging the heater hoses because I saw they were riding on the top of the alternator. I guess I got a hold of the dark blue field wire and pulled it off it's spade connector on the alternator. It made a bright blue spark. Wasn't expecting that. The engine kept running but I went around and turned it off.

Now I've got no spark. Just cranks.

I know the wire runs to the ballast resistor and from there over to the positive side of the coil and to the ignition switch.

A splice from it runs to the voltage regulator.

Another splice before the BR runs to the ignition switch.

And other indicators such as brake and oil.

I haven't even really begun to check anything yet. My first inclination was that I screwed up the coil but it did run until I turned it off. I do have a Pertronix conversion module in the distributor. I suppose that may have fried but again it did keep running.

Any ideas are appreciated.
 
Since it runs to the ballast resistor, I bet you've fried the resistor unless you've by-passed it. Try replacing it and it should run.
 
I am not near my computer to look at the diagram but I know that there are 2 circuits that go to the coil. The crank circuit bypasses the ballast resistor and provides full battery voltage to the coil positive connection so that engine will start easier when cold. The second circuit comes into play when you release the key and sends the voltage through the ballast resistor thus lowering the voltage to the coil and in the process saving the coil from being over heated. It looks like you have an open in the crank ignition 1 circuit. The car was already running off of the ignition 2 circuit when you had the incident. You are probably not getting voltage when you are cranking. You can verify this by jumping battery voltage to the coil and then cranking the car. If it starts then disconnect the wire if it keeps running then your ignition 2 circuit (through the ballast) is okay. The fact that it started with a jumper indicates that there is an open in the ignition 1 circuit. Might be an ignition switch. I will look at the diagram when I get home.
 
Yeah, the BP is bypassed for the Pertronix conversion. That was four years ago.

I get what you're saying about the two circuits. That does make sense. Just jump 12 volts to the positive terminal on the coil and try cranking?
 
yes, called hotwiring, but if you bypassed the ballast resistor, this will now bypass the ignition switch, about the only other thing I can think of since it continued to run
 
Reseat bulkhead connector.
Unlikely to fry the ignition by pulling field wire.... possible, but very unlikely.
 
Like they say where I come from.

"Whoops"
 
Yup! Whoops! I was surprised by the brightness of the spark and thought, uh oh. It wasn't like spark plug bright at all but having never pulled that wire before either I don't know what it may have affected.

I haven't had time to try anything yet. I'm off through Tuesday so I'll have time coming up. I just need to work through it and find out where the fault is. Just gathering ideas right now. My first thought was something electronic and not wiring or a contact. Just need to get on it.
 
Sounds like you have 2 field terminals on your alternator. 1970 was a transition year to that. The IGN feed comes from the key switch, thru the bulkhead connector. Perhaps the key switch terminals were zapped. It might have continued running because once a spark is started, it continues, but not enough contact in the switch to re-establish it. I think 1970 still had the key switch in the dash, so easy to remove. Once it was moved to the steering column (for lock), replacement become more challenging.
 
Yup! Whoops! I was surprised by the brightness of the spark and thought, uh oh. It wasn't like spark plug bright at all but having never pulled that wire before either I don't know what it may have affected.

The alternator field is an electro-magnet with a large amount of inductance. If the field current is broken, the energy stored in the inductor is released, it goes to high voltage in attempt to keep the current flowing. The voltage can easily reach hundreds of volts, resulting in the spark. Ignition coils work in a similar fashion, but also have secondary windings, that transform the voltage to an even greater value. Yes it can damage other electronic devices, but that depends on the source impedance of the wiring back to battery. The higher the source impedance, the more voltage is induced in the IGN circuit.
 
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