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Or disconnect it on one end, and with the key off read resistance across it. It should read 1.5 ohms.
 

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Trifive Automotive Electrical Wiring Expert
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With a volt meter should be 12v from switch 6-8 coming out.
If the points are open, it will read 12 volts on both ends.
If the ballast resistor is open, it will start, but dies as soon as you let the key out of the start position.
 

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Trifive Automotive Electrical Wiring Expert
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Thought so. Thanks I have 12 at both ends I guess I have to go looking for one now that has the screws, like original
That may be normal. See above post.
Temporiarly short the - terminal (distributor wire) to ground and it should go to 6-8 volts.
 

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Discussion Starter #7
If the points are open, it will read 12 volts on both ends.
If the ballast resistor is open, it will start, but dies as soon as you let the key out of the start position.
I mounted the resistor with power in and no wire on other end, both read 12 v
 

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Don should chime in...But, if my electronics memory serves me correctly, you are seeing that 12V because the resistor is not connected to complete the circuit and has no current flowing through it.
 

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Start the engine & let it run for a few minutes to heat the resistor then check in / out voltage engine running.
 

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Trifive Automotive Electrical Wiring Expert
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I mounted the resistor with power in and no wire on other end, both read 12 v
That is normal. The resistor is OK. As Pop's said, a resistor will not drop any voltage unless it is conducting current. Connect the coil and momentarily ground the minus side while reading the voltage. It will give you the voltage drop of your coil.
With the engine running, it will not be an accurate reading of voltage drop, because it is averaging between the points closed (conducting current) and the points open (12 volts).
 

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Discussion Starter #11
That is normal. The resistor is OK. As Pop's said, a resistor will not drop any voltage unless it is conducting current. Connect the coil and momentarily ground the minus side while reading the voltage. It will give you the voltage drop of your coil.
With the engine running, it will not be an accurate reading of voltage drop, because it is averaging between the points closed (conducting current) and the points open (12 volts).
Great
info guys, thanks. I had no idea how that works. Just hooked me up and they worked,👀
 

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Resistors are either closed and working, or open and no voltage output. They don't short internally and read straight through. As I mentioned before, the best test is reading end to end with one wire removed using an ohm meter. 1.5 ohms resistance.
 

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Discussion Starter #14
If the points are open, it will read 12 volts on both ends.
If the ballast resistor is open, it will start, but dies as soon as you let the key out of the start position.
I found a post that told where all the wire ends connected to the coil etc and now I’ve lost it. Can you tell me where that is? Like where the green goes etc.
 

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Trifive Automotive Electrical Wiring Expert
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Brown wire connects to the top of the ballast resistor, dark green to the bottom of the resistor. A different dark green connects to the + (plus) coil, black wire from the distributor connects to the - (minus) coil.
 

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PROPER resistance is done with one wire disconnected, and the meter leads across the resistor, and THE CORRECT READING AT ROOM TEMP SHOULD BE 1.80 OHMS, +/- 1 PERCENT.
 

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Thought so. Thanks I have 12 at both ends I guess I have to go looking for one now that has the screws, like original
That most likely means it's good, just that the points are open. There is no voltage drop unless there is a load on it.
 

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PROPER resistance is done with one wire disconnected, and the meter leads across the resistor, and THE CORRECT READING AT ROOM TEMP SHOULD BE 1.80 OHMS, +/- 1 PERCENT.
1% tolerance? Room temperature? Is that the factory specs? Right or wrong I'd like to see those specs!
 

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Trifive Automotive Electrical Wiring Expert
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How many people on this site do you think have a ohm meter that reads accurately to .018 ohms or even within 50% of 1.8 ohms.
I prefer testing voltage under operating conditions instead of using a ohmmeter.

See post #5.
 
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