6 volts to coil constant

oldspert

oldspert

Senior Member
Is there supposed to be 6 volts to ground on both sides of my 29 coil. Switch is off but if I put a meter on the coil terminals, I get 6 volts to ground, both sides. I do not have a wiring diagram to trace out the circuit.
 
That’s normal, one of the checks is to see voltage to both primary posts. The power is broken at the switch.
 
6 V at both primary wires on the coil. Turn on the ign switch and slowly turn the engine over with the hand crank, when points close the point side of the coil should go to a solid ground, other side of coil should stay at 6v.
 
if the ignition key is "off" - or if the key is "on" and the points are open- you should get full battery voltage (6 or 12 dependent on battery) on each coil contact post if you are measuring their voltage to ground . This simple diagram may help.
 

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  • 1. original ign circuit (Nov 1927 onwards ).jpg
    1. original ign circuit (Nov 1927 onwards ).jpg
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The test light provides a ground to any circuit that is hard wired to the power side of the battery. With a lot of modern ignition switches in use now days, there may be some that control the power side of the coil instead of the ground breaker side.
 
Oldspert, based on the tests you ran with the volt meter your car is still wired as it was originally. The wringing diagram on post 4 is correct for your car.
 
I like the more modern wiring where the power is disconnected from the coil when the ignition is off. A wire goes from the ammeter side of the junction box to the ignition switch then to the coil and from the coil to the points and condenser. I just think it is safer. Ford was concerned about people stealing his cars. That is a minor concern in this day and age.
 
Cold yes, warm no. The resistance coil should drop the voltage on one side after the coil gets up to temperature.
 
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