The Ford Barn

chkolar · 05-13-2023, 12:59 PM

Hi Guys. I need your help again. I wanted to build up a couple of distributors to carry in my car. I replaced all the parts with modern points and new lower plate with longer wire. The first one I installed worked perfectly, but the second one wouldn't start the car. When checking for voltage, there was power at both sides of the coil but when I turned on the key, there was power on the drivers side of the coil but no power on the passenger side of the coil. What do you think?

Patrick L. · 05-13-2023, 02:11 PM

Seems like the primary lead is grounding somewhere. Keep disconnecting from inside distributor back until you find power.

Keith True · 05-13-2023, 02:44 PM

Put a piece of paper between the points and see if it still does it.

nkaminar · 05-13-2023, 04:32 PM

If one side is still at zero volts after putting the paper between the points then you have a ground where there shouldn't be one.

rotorwrench · 05-13-2023, 04:57 PM

Check between the two small terminals with an Ohm meter. It should about 1.5 Ohms give or take a little. If not then it may be damaged. The coil is basically an electromagnet when it is connected to a battery. It won't induct a high tension response unless the ground side it disconnected such as is accomplished by the breaker points. On the car, the points have to be closed to energize the coil. If the points are open, touching a test light to the ground terminal will complete a circuit and the test lamp will light up due to the ground lead on the test light. A coil that is bad with an open in the primary will not function.

bobbader · 05-13-2023, 07:29 PM

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Before anyone else gets the idea that this lack of "power" on one side of the coil with the key on ............. THIS IS NORMAL ................ if the points are closed with the key turned on, the loss of "power" to one side of the coil is normal. This is why 2 posters have suggested putting a piece of paper between the points. Actually, the "power" is still there but has now gone to "short" with the points closed. Depending on which pole on the coil the short primary coil wire from the terminal box is mounted, this "short" will show as a discharge on the ammeter as soon as the key is turned on. Likewise, if it shows discharge with the key on, it will not show the same discharge if you bridge the points with a piece of paper.

rotorwrench · 05-14-2023, 08:36 AM

"Short" may not be the best way to describe it. The coil is a load if the circuit is completed to it. It will also overheat if the points don't open and close like they do when the motor is running. Many a coil has died a hard death due to inadvertently leaving the ignition on with the points closed. It also drains the battery in short order.

bobbader · 05-14-2023, 09:09 AM

Rotorwrench, thanks for your followup on my post. I called it a "short" without suggesting that, as such, it could drain the battery and/or "cook the coil" if left unchecked. Good catch!

MAG · 05-14-2023, 05:06 PM

You did a good job on the 1st distributor. Go back to the 2nd distributor you rebuilt and look closely where the wire coming up from the lower plate is attached to the points. Make sure it is not grounded there.

Rob Doe · 05-14-2023, 09:17 PM

chkolar, X2 all above posts. What year is your car? Adding a bit to Bob's post #6, In November of 1929, there was a wiring change made by Ford Motor Co. They moved the source of the black wire that attaches to the - post of the coil from the yellow wire side of the terminal box to the yellow with black stripe side.

This allows the functioning / opening and closing of the ignition points / proper grounding and ungrounding of the points to be reflected on the ammeter as a slight repetitious discharge as the engine is being cranked over to start the car. When at slow idle it will also show up as a negative jiggle in the ammeter needle. Not all A's have this service bulletin applied.

If your car is wired, (stock, with Service Bulletin applied) a short / unintended ground, as mentioned in previous posts will show on the ammeter as a small, but steady discharge, approx 4 amp or two marks on the ammeter???

Check your terminal box and make sure the black coil wire is connected to the yellow black stripe side. With the points blocked open with a business card or folded piece of paper, if you see the discharge, something is prematurely grounded between the + post of the coil (red wire) and the blocked open points.

You had the distributor out, and you screwed the ign. cable into the side of the distributor. It can be too tight and cause the buss bar to contact the casting, etc. 2.5 or maybe 3 turns is usually enough. If the cable is old the spring loaded end may be too stiff and stuck, or stuck shy of the buss bar (under the lower plate) and thus is an open circuit and not visible on the ammeter (no discharge).

Report back on your findings. There are common ways to bypass the switch and the ignition cable etc. and / or work backwards from the blocked open points arm with the VOM as suggested in post #2, connection by connection to isolate the fault.

Good luck.

JKY · 05-15-2023, 10:12 AM

Quote:

Originally Posted by Keith True

Put a piece of paper between the points and see if it still does it.

This is correct!

chkolar · 05-17-2023, 08:30 AM

I discovered that since I was using modern points, the condenser was located on top of the upper plate and the tab used for the original condenser on the lower plate was not being used. The unused tab was touching the distributor housing causing a short. I bent the tab so that it was not contacting the housing and everything work out beautifully. Thanks to all of you that responded.

05-13-2023, 12:59 PM	#1
chkolar Junior Member Join Date: Jul 2012 Posts: 28	no power at coil Hi Guys. I need your help again. I wanted to build up a couple of distributors to carry in my car. I replaced all the parts with modern points and new lower plate with longer wire. The first one I installed worked perfectly, but the second one wouldn't start the car. When checking for voltage, there was power at both sides of the coil but when I turned on the key, there was power on the drivers side of the coil but no power on the passenger side of the coil. What do you think?

05-13-2023, 02:44 PM	#3
Keith True Senior Member Join Date: May 2010 Location: Epping N.H. Posts: 2,987	Re: no power at coil Put a piece of paper between the points and see if it still does it.

05-13-2023, 04:32 PM	#4
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,897	Re: no power at coil If one side is still at zero volts after putting the paper between the points then you have a ground where there shouldn't be one. __________________ 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.

05-13-2023, 04:57 PM	#5
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,426	Re: no power at coil Check between the two small terminals with an Ohm meter. It should about 1.5 Ohms give or take a little. If not then it may be damaged. The coil is basically an electromagnet when it is connected to a battery. It won't induct a high tension response unless the ground side it disconnected such as is accomplished by the breaker points. On the car, the points have to be closed to energize the coil. If the points are open, touching a test light to the ground terminal will complete a circuit and the test lamp will light up due to the ground lead on the test light. A coil that is bad with an open in the primary will not function.

05-14-2023, 08:36 AM	#7
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,426	Re: no power at coil "Short" may not be the best way to describe it. The coil is a load if the circuit is completed to it. It will also overheat if the points don't open and close like they do when the motor is running. Many a coil has died a hard death due to inadvertently leaving the ignition on with the points closed. It also drains the battery in short order.

05-13-2023, 02:11 PM	#2
Patrick L. Senior Member Join Date: May 2010 Location: Largo Florida Posts: 7,225	Re: no power at coil Seems like the primary lead is grounding somewhere. Keep disconnecting from inside distributor back until you find power.

05-13-2023, 07:29 PM	#6
bobbader Senior Member Join Date: May 2010 Location: Huntington, NY Posts: 271	Re: no power at coil Sponsored Links (Register now to hide all advertisements) Before anyone else gets the idea that this lack of "power" on one side of the coil with the key on ............. THIS IS NORMAL ................ if the points are closed with the key turned on, the loss of "power" to one side of the coil is normal. This is why 2 posters have suggested putting a piece of paper between the points. Actually, the "power" is still there but has now gone to "short" with the points closed. Depending on which pole on the coil the short primary coil wire from the terminal box is mounted, this "short" will show as a discharge on the ammeter as soon as the key is turned on. Likewise, if it shows discharge with the key on, it will not show the same discharge if you bridge the points with a piece of paper.

05-14-2023, 09:09 AM	#8
bobbader Senior Member Join Date: May 2010 Location: Huntington, NY Posts: 271	Re: no power at coil Rotorwrench, thanks for your followup on my post. I called it a "short" without suggesting that, as such, it could drain the battery and/or "cook the coil" if left unchecked. Good catch!

05-14-2023, 05:06 PM	#9
MAG Senior Member Join Date: May 2010 Location: Austin, Texas Posts: 925	Re: no power at coil You did a good job on the 1st distributor. Go back to the 2nd distributor you rebuilt and look closely where the wire coming up from the lower plate is attached to the points. Make sure it is not grounded there. __________________ I noticed the harder I work the luckier I get!

05-14-2023, 09:17 PM	#10
Rob Doe Senior Member Join Date: Apr 2021 Location: Central Illinois Posts: 490	Re: no power at coil chkolar, X2 all above posts. What year is your car? Adding a bit to Bob's post #6, In November of 1929, there was a wiring change made by Ford Motor Co. They moved the source of the black wire that attaches to the - post of the coil from the yellow wire side of the terminal box to the yellow with black stripe side. This allows the functioning / opening and closing of the ignition points / proper grounding and ungrounding of the points to be reflected on the ammeter as a slight repetitious discharge as the engine is being cranked over to start the car. When at slow idle it will also show up as a negative jiggle in the ammeter needle. Not all A's have this service bulletin applied. If your car is wired, (stock, with Service Bulletin applied) a short / unintended ground, as mentioned in previous posts will show on the ammeter as a small, but steady discharge, approx 4 amp or two marks on the ammeter??? Check your terminal box and make sure the black coil wire is connected to the yellow black stripe side. With the points blocked open with a business card or folded piece of paper, if you see the discharge, something is prematurely grounded between the + post of the coil (red wire) and the blocked open points. You had the distributor out, and you screwed the ign. cable into the side of the distributor. It can be too tight and cause the buss bar to contact the casting, etc. 2.5 or maybe 3 turns is usually enough. If the cable is old the spring loaded end may be too stiff and stuck, or stuck shy of the buss bar (under the lower plate) and thus is an open circuit and not visible on the ammeter (no discharge). Report back on your findings. There are common ways to bypass the switch and the ignition cable etc. and / or work backwards from the blocked open points arm with the VOM as suggested in post #2, connection by connection to isolate the fault. Good luck. __________________ "It ain't what you know for certain that gets ya in trouble. It's what ya know for certain that just ain't so!" Last edited by Rob Doe; 05-15-2023 at 03:17 AM.

05-17-2023, 08:30 AM	#12
chkolar Junior Member Join Date: Jul 2012 Posts: 28	Re: no power at coil I discovered that since I was using modern points, the condenser was located on top of the upper plate and the tab used for the original condenser on the lower plate was not being used. The unused tab was touching the distributor housing causing a short. I bent the tab so that it was not contacting the housing and everything work out beautifully. Thanks to all of you that responded.