Over the mini starter wiring

Theiskell

The Hillbilly
Joined
Apr 1, 2008
Messages
83
Location
Liberty Mo
Ok , here is what I have; a 69 with the motor out at the moment. I am going to put a mini starter in with the new motor. So I thought it would be a good idea to get some of the wiring done that I needed to do. I have installed a relay to supply the coil 12v at startup. No biggie right! WRONG!!!
I get everything wired in turn the key switch to the on position and check the wire coming from the firewall to the coil for power. I am expecting to see around 4v on this wire, Do you think that is what I found HELL NO it has 12v on it. I thought that wire was a resistor wire? Anyway I know it needs a lower voltage when the car is running. So what do I do from here? Put a resistor in line? Figure out why I have 12 volts on a resistor wire? Or burn this mother f'r to the ground? As always any help is appreciated.
 
The coil wire needs to be around 8 or so volts w/ engine running, 12 for starting (switched from starter relay). All you need is a ballast resistor or an ign. box to bring the voltage down. Resistor wires, never use them. Always an ign. box.

Now, 4 amps? Huh ? :huh2::huh:
 
V8 coils are usually 1.5 ohms. The matching ballast resistor is 1.5 ohms. 3 ohms total. 12volts/3 ohms=4 amperes. Upon start up, the starter/shunt relay enables 12volts/1.5ohms=8amperes. Usually, the starter draws the supply voltage down, and this value can be lower.
The points see 12 volts. Upon opening, this can jump to upwards of 300 volts due to the collapsing field in the coil. The condenser's job is to prevent this energy from arcing across the opened points.
You might see 9 volts with a VOM, but with a scope you will see 12.
If your original coil wire is intact, it will have approxamately 1.2-1.7 ohms. It's fine. It ran that way for years, and will continue to do so.
If you are unsure, I can give you a NAPA part# for an external unit. Then, used any keyed fused source.
 
The coil wire needs to be around 8 or so volts w/ engine running, 12 for starting (switched from starter relay). All you need is a ballast resistor or an ign. box to bring the voltage down. Resistor wires, never use them. Always an ign. box.

Now, 4 amps? Huh ? :huh2::huh:

Someone told me that the amperage was reduced not the voltage .:suspicious:


Whew my head is killing me on this. I don't have the engine in would that make a difference? So for me not to burn up my coil I need 8 volts with the key in the on position. Does that sound right? I have the relay wired in to supply 12v when the key is in the "start" position. To my knowledge the original wire from the firewall has not been messed with so why would it have 12 v on it. Should I hook up just the coil and check the voltage then?
 
Someone told me that the amperage was reduced not the voltage .:suspicious:


Whew my head is killing me on this. I don't have the engine in would that make a difference? So for me not to burn up my coil I need 8 volts with the key in the on position. Does that sound right? I have the relay wired in to supply 12v when the key is in the "start" position. To my knowledge the original wire from the firewall has not been messed with so why would it have 12 v on it. Should I hook up just the coil and check the voltage then?

If your running the engine on a test stand, I suggest an external resistor of 1.5 ohms.
 
Bird, you have restored my faith in mankind. I have spent so much (wasted)time on "another forum" trying to explain how automotive ignition systems work. I break it all down, and they keep coming back with nonsense. On more than one occasion I have just given up trying to explain it all. You are among about three people I have ever met who understands the way the system works. Keep up the good work.
 
V8 coils are usually 1.5 ohms. The matching ballast resistor is 1.5 ohms. 3 ohms total. 12volts/3 ohms=4 amperes. Upon start up, the starter/shunt relay enables 12volts/1.5ohms=8amperes. Usually, the starter draws the supply voltage down, and this value can be lower.
The points see 12 volts. Upon opening, this can jump to upwards of 300 volts due to the collapsing field in the coil. The condenser's job is to prevent this energy from arcing across the opened points.
You might see 9 volts with a VOM, but with a scope you will see 12.
If your original coil wire is intact, it will have approxamately 1.2-1.7 ohms. It's fine. It ran that way for years, and will continue to do so.
If you are unsure, I can give you a NAPA part# for an external unit. Then, used any keyed fused source.


BB,
You replied while I was replying. I guess my bottom line question is. Do I need to reduce the voltage on the wire coming from the firewall? If the answer is yes. what is the best way to do that? I am guessing a ballast resistor. If so where would I get such an animal. Sorry for the ignorance here :smash:
 
Bird, you have restored my faith in mankind. I have spent so much (wasted)time on "another forum" trying to explain how automotive ignition systems work. I break it all down, and they keep coming back with nonsense. On more than one occasion I have just given up trying to explain it all. You are among about three people I have ever met who understands the way the system works. Keep up the good work.

Thanks. My pop was a naval aviation ignition specialist in WWII. He taught me alot before he passed on. I give him the credit.
 
No stand just getting the car ready to drop the new engine in

If the car was previously wired with no trouble, chances are the resistor wire is intact. If you don't know, I will need to know the color/circumstances for your concern.
 
If the car was previously wired with no trouble, chances are the resistor wire is intact. If you don't know, I will need to know the color/circumstances for your concern.

Using a DVM I show 12v on the resistor wire with it not hooked up to the coil. is that ok
 
Bird, you have restored my faith in mankind. I have spent so much (wasted)time on "another forum" trying to explain how automotive ignition systems work. I break it all down, and they keep coming back with nonsense. On more than one occasion I have just given up trying to explain it all. You are among about three people I have ever met who understands the way the system works. Keep up the good work.

MAKE that TWO of us trying to esplain the same thing....but I got tired of it also....too lazy to do a search or a google or something for the obvious, well me tired too.....got a post here in ridecule of the 'knowledge' base over there even yet, even....

:clobbered::bounce::trumpet:
 
Thank you!!

Theiskell, you gotta remember to treat a COIL, of wire, ANY coil and even a wire length (in theory) as having a peculair property that is totally aside from resistance like we measure with a DVM .....that is called inductance, which is important ONLY when current is applied and then disconnected....like across points or a electronic sending unit...modlule, HEI, MSD, etc....

or any AC current source like your house has.....

coild react funny to voltages applied it not ramps up currents the way a pure resistive load would....the coil is VERY high impedance (resistance) to the application of voltage across it, BUT the longer the voltage stays applied, the more current is drawn, so the voltage drops, or currents go up very rapidly...the voltage drops ONLY if there is a significant resistor in series with the coil, it's there to keep the coil from burning up and disabling the car....IF the points are closed and ignition ON, or the dwell is of too many degrees if the rubbing block allows the gap to close too much.....

as well as various other electroic reasons that COULD be gotten around by designs...but forget about that for now....


the POWER into the coil is not linear, the way you think of a lightbulb lighting up when you turn on/off the switch,

so the amps vary a LOT, and so we leave it alone for now....

clear as mud?? no snowballing, hope it esplains a bit....

:bounce:
 
Here's one for you Gene. A healthy point type ignition has a blue spark. What does an orange spark denote?
 
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