Need Coil Voltage Help 140 / 3.0

[Alumarine]

I'm going through my wiring and thought I'd check my coil voltage.
I'm confused with the results.

With the motor running at 1000rpm and Voltage at Battery is 14.37
At Coil Pos and Block I get 11.9 volts
At Coil Pos and Coil Neg I get 1.39 volts
At Coil Pos and Battery Neg I get 11.9 volts

If I start the motor at idle speed without the alternator kicking in I get these results
Battery voltage is 12.45
At Coil Pos and Block I get 9.99 volts
At Coil Pos and Coil Neg I get 1.28 volts
At Coil Pos and Battery Neg I get 9.99 volts

I disconnected the purple wire from the S terminal on the starter and got the same results.

Ballast wire resistance is 1.9 ohms. Motor serial is 5668920

I've included a picture of my alternator connections as well.
Do I have issue or am I just imagining an issue? Thanks

 

[alldodge]

Don't see an issue

I disconnected the purple wire from the S terminal on the starter and got the same results.

This wire should be a Purple/Yellow, but should change nothing except when starting

The purple coil wire (resistance one) is just limiting the current going to coil and points. There is a voltage drop when running so your good

IMO

 

[Alumarine]

Thank you. And yes it was purple/yellow.
I was thinking it should have been 9.9 volts always but I think you're saying that it's the current drop that is important and the fact that there is a voltage drop indicates that there is a current drop as well?

 

[Scott Danforth]

With the motor running at 1000rpm and Voltage at Battery is 14.37 - a bit high, check your connections on the alternator sensing wires
At Coil Pos and Block I get 11.9 volts - a bit high, however tied to your battery voltage
At Coil Pos and Coil Neg I get 1.39 volts - you should have 0 volts here, check your ground connections at the points/dizzy and the wire at the coil
At Coil Pos and Battery Neg I get 11.9 volts

If I start the motor at idle speed without the alternator kicking in I get these results
Battery voltage is 12.45 - check your connections
At Coil Pos and Block I get 9.99 volts - about right with a resistance wire.
At Coil Pos and Coil Neg I get 1.28 volts- you should have 0 volts here, check your ground connections at the points/dizzy and the wire at the coil
At Coil Pos and Battery Neg I get 9.99 volts

 

[alldodge]

I was thinking it should have been 9.9 volts always but I think you're saying that it's the current drop that is important and the fact that there is a voltage drop indicates that there is a current drop as well?

Yes there is a voltage drop, and if the points were open and the motor was off you would see closer to the 9.9V

Once motor is running and the ALT is producing 14+V then the voltage will be higher

 

[achris]

Yes there is a voltage drop, and if the points were open and the motor was off you would see closer to the 9.9V No, you should see battery voltage when the points are open, and the divided voltage between the resistance wire and the coil resistance when the points are closed.

Once motor is running and the ALT is producing 14+V then the voltage will be higher. What you see on the meter will depend on the meter. Is it an analogue meter (old needle jobbie) or a digital? If it's a digital, is it displaying peak, RMS or average voltage? The actual voltage will be a square wave, with the mark-space ratio that of the points dwell. The 'average' voltage will be a produce of that mark-space ratio, and the divided voltage between the resistance wire and the coil resistance.

Chris.......

 

[Alumarine]

Thanks guys, I won't be able to look at it again for a week or so.

Scot that battery voltage of 12.45 before the alternator kicks in is with the battery powering the coil and gauges.
The battery is 12.6 when the motor is off.

Chris it's a $100 dwell/tach/mutlimeter and I don't know how it measures the voltage.
I'll dust off my Simpson 260 analogue and see what I get with it.