11 volts to coil instead of 8 volts

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Joined
Apr 11, 2011
Messages
95
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8
Location
Kennewick Washington USA
My Car
1971 fastback
With the engine running I measure 11 volts from the positive terminal on coil to engine ground.  With the key in run and coil wire disconnected from the positive terminal I measure 11.6 volts to engine ground.  The coil that has been in the car for years boiled and the fan blew oil all over the place.  Replaced coil with a 1.5 ohm Flamethrower and engine runs but wonder why I don't have somewhere around 8 volts to coil.  Removed fuse F4 and measured the resistance on wire 16 through tach and resistor wire to disconnected coil wire and get 2.6 ohms.  Has anybody else ever measured this?  Does this seem like the correct resistance?

 
I do have a tach and it does work.  The resistor wire is supposed to be 1.3 to 1.4 ohms so I figured the additional ohms are from the tach resistance.  Trying real hard to not open the dash again to check the wire separately.  Has anybody got access to a tach to measure the resistance?

 
Unplug the wire from the "I" terminal on the starter solenoid and measure the voltage again. If you're getting nominal voltage, replace the solenoid.

 
Resistor wire should be 1.3 to 1.7 ohms with a perfect meter; most meters are good to about 0.5 ohms or so, so 2.3 ohms is acceptable. I wouldn't be concerned.

With the coil wire removed, and the key in RUN, there is no current to the coil so you'll see full voltage. I typically see 10.5-11 V at the + side of the coil while the engine is running. It actually fluctuates between 0 and battery voltage as the points closes and opens. 9V is the minimum for the engine to run.

You're good to go. Nothing to worry about...nothing here to see...move along, folks,..

 
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