distributor ignitions

tomturkey · Sep 4, 2023

I posted recently about converting a tractor to 12 volt negative ground. Having accomplished that task. I now have another question for the members here who seem to have most of the answers. In the mid to late 50's into the 60's automobiles changed to a 12 volt negative ground electrical system.
What changes were made within the distributor to handle the 12 volt system. I do not recall seeing resistors on any. more silly questions from tom gobble

rvirgil_KS · Sep 4, 2023

What changes were made within the distributor to handle the 12 volt system.

None. Points and condenser don't care whether they operate on 6 or 12 volt. However, points and coil do care about current going through the circuit. Voltage doubles current doubles. That's the reason for the added resistor in the coil supply line, or changing to a direct 12 volt coil.

55 50 Ron · Sep 4, 2023

The change was the coil. 6 volt coils were a certain resistance and the 12 volt coils were approximately twice the resistance of the 6 volt coil. The added resistance is in the wire of the 12 volt coil. That's why you don't see a physical resistor.

rustred · Sep 4, 2023

none, that would have been in 1955 , as when the new body style came out in the chev 1/2 tons is how i remember the switch. even in the tractors it was around middle 50's. i have the 44 special and its 6 volt and the next model 444 snd its 12 volt, same as ihc in the middle 50's. same distributors.

Rich'sToys · Sep 4, 2023

Whether positive or negative ground will determine which side of the coil is hooked to the wire coming from the distributor.

kencombs · Sep 4, 2023

I can't recall any 12v cars/trucks in the 50s/60s that did not have some way to reduce the voltage to the 8v range when running and full 12v to the coil when starting
. I guess it's more accurate to say that they reduced the current to around 4 amps running.
Lots of different ways were used to do that. Some early Chrysler products had a thermister(heat sensitive resister) in the base of the coil, out of sight, Later ones had it on the firewall as did Ford and GM. GM also use a high resistance wire from the ignition switch to the coil on some models.

Geo-TH,In · Sep 4, 2023

I guess it's more accurate to say that they reduced the current to around 4 amps running.

You are right, the primary current was close to 4 amps. My ballast resistor was mounted on the firewall.

During starting, the ballast was bypassed and the full 12v was sent to the coil for a hotter spark.

Rarely do YT members bypass the ballast when they convert from 6 to 12v.

olddavid · Sep 5, 2023

(quoted from post at 11:55:42 09/04/23) Some early Chrysler products had a thermister(heat sensitive resister) in the base of the coil, out of sight, Later ones had it on the firewall as did Ford and GM. GM also use a high resistance wire from the ignition switch to the coil on some models.

I learned to carry a spare firewall mounted resistor for those electronic ignition Chrysler units. They were known to fail and cause a no start condition. Come to think of it the electronic ignition control was prone to failure as well. I carried a spare and it bailed me at least once when the car just quit running while on the highway. Points you could fiddle with and usually get the car running but if the ignition module conked out you were done if you didn't have a spare.

distributor ignitions

tomturkey

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rvirgil_KS

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55 50 Ron

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rustred

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Rich'sToys

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kencombs

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Geo-TH,In

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olddavid

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