The Ford Barn

Canton_Model_A's · 06-20-2024, 11:24 AM

Folks:
I have a converted 1929 'A' over to 12v negative ground. after doing some work on it with other 'odd' issues, I have seen thru the suppliers that they sell a coil that doesn't require the ballast resistor. I had issues when I was bringing it out of storage and had already replaced the coil as it wasn't getting spark thinking that was the issue. Turned out the ammeter was faulty.

I am trying to re-wire it back to as much stock as I can, I have installed a brand new wiring harness and it has the 12v alternator. why would I require the Ballast resistor in the loop or can I use the resistor-less coil from the suppliers.

ps.
I did NOT do the conversion to 12v so I don't even know what is involved with that conversion.

nkaminar · 06-20-2024, 12:10 PM

Some coils have the ballast resistor built in.

katy · 06-20-2024, 12:37 PM

Measure the resistance of the primary winding of the coil, aprox 1.5 ohms would be a 6 volt coil, aprox 3 ohms would be a 12 volt coil.

Badpuppy · 06-21-2024, 07:27 AM

Use a 12 volt coil, no resistor. The only wiring differences for negative ground are polarity of ammeter and coil are reversed.

Canton_Model_A's · 06-21-2024, 07:58 AM

does anyone here behind the barn have any sort of wiring diagram on what a properly converted Model A should be? I am trying to fix all the PO's work and want to do it right

larry harding · 06-23-2024, 03:53 PM

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i converted my 31 pu and recent speedster to 12v. i went round and around with guys at local parts suppliers trying to get a 12 v coil with built in resistor, if you can't tell them what year it was used on they are lost. they sold me coils for around $40.00 dollars that still required external resister for 12 v. use. finally i found the correct coil on amazon with built in resistor for a lot less money. it is sold as a coil for converting ford tractors to 12v. BINGO! that is what i was wanting and for a lot less money than the local cog house wanted for coils that wouldn work.

katy · 06-23-2024, 04:57 PM

Quote:

Originally Posted by larry harding

i converted my 31 pu and recent speedster to 12v. i went round and around with guys at local parts suppliers trying to get a 12 v coil with built in resistor, if you can't tell them what year it was used on they are lost. they sold me coils for around $40.00 dollars that still required external resister for 12 v. use. finally i found the correct coil on amazon with built in resistor for a lot less money. it is sold as a coil for converting ford tractors to 12v. BINGO! that is what i was wanting and for a lot less money than the local cog house wanted for coils that wouldn work.

Good intel, tnx.

Badpuppy · 06-24-2024, 08:13 AM

Quote:

Originally Posted by Canton_Model_A's

does anyone here behind the barn have any sort of wiring diagram on what a properly converted Model A should be? I am trying to fix all the PO's work and want to do it right

Use the standard wiring diagram you will find many places. Just note reversals of battery, ammeter and coil. Horn, coil and electric wipers will need to be 12 volts. All 3 6v parts can be used, with a dropping resistor of proper value for each.

larry harding · 06-24-2024, 09:56 AM

the reason i beat the bushes to find a coil with internal resistor is no wanting to see a resistor looking so out of place on the firewall, remember the 55 and later gm cars with the resistor on the firewall. i know they were running 6 v, coils on 12 v. in series with a resistor, but there it hung for several years.

06-20-2024, 11:24 AM	#1
Canton_Model_A's Senior Member Join Date: Sep 2022 Location: Canton, Michigan Posts: 321	12v Converted 1929 'A' Folks: I have a converted 1929 'A' over to 12v negative ground. after doing some work on it with other 'odd' issues, I have seen thru the suppliers that they sell a coil that doesn't require the ballast resistor. I had issues when I was bringing it out of storage and had already replaced the coil as it wasn't getting spark thinking that was the issue. Turned out the ammeter was faulty. I am trying to re-wire it back to as much stock as I can, I have installed a brand new wiring harness and it has the 12v alternator. why would I require the Ballast resistor in the loop or can I use the resistor-less coil from the suppliers. ps. I did NOT do the conversion to 12v so I don't even know what is involved with that conversion. __________________ --------------------------------------- 1929 Model A Tudor - "Darla" '29 Model A: Old enough to start with a crank, young enough to steal the show! "Stay away from negative people, they have a problem for every solution" Model A Ford Club of America Model A Restorers Club Motor City A's Club

06-20-2024, 12:10 PM	#2
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 5,859	Re: 12v Converted 1929 'A' Some coils have the ballast resistor built in. __________________ 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.

06-20-2024, 12:37 PM	#3
katy Senior Member Join Date: Jun 2015 Location: Red Deer, Alberta Posts: 5,715	Re: 12v Converted 1929 'A' Measure the resistance of the primary winding of the coil, aprox 1.5 ohms would be a 6 volt coil, aprox 3 ohms would be a 12 volt coil. __________________ If you don't hear a rumor by 10 AM, start one!. Got my education out behind the barn!

06-21-2024, 07:27 AM	#4
Badpuppy Senior Member Join Date: Dec 2017 Location: Guthrie, OK Posts: 1,247	Re: 12v Converted 1929 'A' Use a 12 volt coil, no resistor. The only wiring differences for negative ground are polarity of ammeter and coil are reversed.

06-21-2024, 07:58 AM	#5
Canton_Model_A's Senior Member Join Date: Sep 2022 Location: Canton, Michigan Posts: 321	Re: 12v Converted 1929 'A' does anyone here behind the barn have any sort of wiring diagram on what a properly converted Model A should be? I am trying to fix all the PO's work and want to do it right __________________ --------------------------------------- 1929 Model A Tudor - "Darla" '29 Model A: Old enough to start with a crank, young enough to steal the show! "Stay away from negative people, they have a problem for every solution" Model A Ford Club of America Model A Restorers Club Motor City A's Club

06-23-2024, 03:53 PM	#6
larry harding Senior Member Join Date: Sep 2015 Location: western n.c. Posts: 437	Re: 12v Converted 1929 'A' Sponsored Links (Register now to hide all advertisements) i converted my 31 pu and recent speedster to 12v. i went round and around with guys at local parts suppliers trying to get a 12 v coil with built in resistor, if you can't tell them what year it was used on they are lost. they sold me coils for around $40.00 dollars that still required external resister for 12 v. use. finally i found the correct coil on amazon with built in resistor for a lot less money. it is sold as a coil for converting ford tractors to 12v. BINGO! that is what i was wanting and for a lot less money than the local cog house wanted for coils that wouldn work.

06-24-2024, 09:56 AM	#9
larry harding Senior Member Join Date: Sep 2015 Location: western n.c. Posts: 437	Re: 12v Converted 1929 'A' the reason i beat the bushes to find a coil with internal resistor is no wanting to see a resistor looking so out of place on the firewall, remember the 55 and later gm cars with the resistor on the firewall. i know they were running 6 v, coils on 12 v. in series with a resistor, but there it hung for several years.