The Ford Barn

oldspert · 05-03-2023, 06:22 PM

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.

Big hammer · 05-03-2023, 06:35 PM

That’s normal, one of the checks is to see voltage to both primary posts. The power is broken at the switch.

eagle · 05-03-2023, 09:59 PM

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.

johnbuckley · 05-04-2023, 03:44 AM

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.

rotorwrench · 05-04-2023, 09:15 AM

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.

MAG · 05-04-2023, 04:04 PM

Sponsored Links (Register now to hide all advertisements)

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.

nkaminar · 05-05-2023, 12:01 PM

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.

redmodelt · 05-06-2023, 01:48 PM

Cold yes, warm no. The resistance coil should drop the voltage on one side after the coil gets up to temperature.

johnbuckley · 05-06-2023, 03:30 PM

Quote:

Originally Posted by redmodelt

The resistance coil should drop the voltage on one side after the coil gets up to temperature.

That's interesting, By how much should it drop?

redmodelt · 05-06-2023, 04:17 PM

Down to about 4 volts.

05-03-2023, 06:22 PM	#1
oldspert Senior Member Join Date: Aug 2012 Location: Texas Posts: 227	6 volts to coil constant 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.

05-03-2023, 06:35 PM	#2
Big hammer Senior Member Join Date: Jun 2014 Location: Land of Lincoln Posts: 3,131	Re: 6 volts to coil constant That’s normal, one of the checks is to see voltage to both primary posts. The power is broken at the switch. __________________ Don't force it with a little hammer tap, tap, tap get a bigger hammer tap done

05-03-2023, 09:59 PM	#3
eagle Senior Member Join Date: Aug 2011 Location: Eagle Bend, MN Posts: 2,025	Re: 6 volts to coil constant 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. __________________ "There are some that can destroy an anvil with a teaspoon and shouldn't be allowed to touch anything resembling a tool."

05-04-2023, 09:15 AM	#5
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,437	Re: 6 volts to coil constant 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.

05-04-2023, 04:04 PM	#6
MAG Senior Member Join Date: May 2010 Location: Austin, Texas Posts: 925	Re: 6 volts to coil constant Sponsored Links (Register now to hide all advertisements) 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 noticed the harder I work the luckier I get!

05-05-2023, 12:01 PM	#7
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,900	Re: 6 volts to coil constant 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. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.

05-06-2023, 01:48 PM	#8
redmodelt Senior Member Join Date: May 2010 Location: Portland OR Posts: 6,342	Re: 6 volts to coil constant Cold yes, warm no. The resistance coil should drop the voltage on one side after the coil gets up to temperature. __________________ I know the voices aren't real but damn they have some good ideas!

05-06-2023, 04:17 PM	#10
redmodelt Senior Member Join Date: May 2010 Location: Portland OR Posts: 6,342	Re: 6 volts to coil constant Down to about 4 volts. __________________ I know the voices aren't real but damn they have some good ideas!