Hi, looking to make sure I installed the proper coil on this tractor. I've read that when a 12v conversion is done, the 6v coil isn't replaced for easier starts. This tractor has a 12v conversion and I can't find the old coil at the moment to confirm what I removed. Can anyone verify this? I'll order a new 6v coil. I installed a 12v coil purchased from napa.
- Thread starter CES
- Start date
Nothing "sentimental" about it. GM did it for years (kept the 6 volt type coil in 12 volt systems). So did John Deere. Using a low-
resistance primary 6 volt-system coil with a resistor and some sort of start-bypass gives more spark potential then using a 12-volt-system
only coil with no added dropping resistor.
My 64 Ford 4000 Industrial with the 172 gasser and 12 volts still has the original coil and has never skipped a beat.
resistance primary 6 volt-system coil with a resistor and some sort of start-bypass gives more spark potential then using a 12-volt-system
only coil with no added dropping resistor.
My 64 Ford 4000 Industrial with the 172 gasser and 12 volts still has the original coil and has never skipped a beat.
rvirgil_KS
Well-known Member
IC14SB coil should have near battery voltage at the input to distributor when points are open and near 0 voltage when points are closed
Your system with a 12 volt battery and alternator needs total coil primary resistance of around 4 ohms. That assuming you still have ignition points. A coil used on a 6 volt system with no external resistor, or on a 12 volt system with an external resistor will have around 1.2 - 2.2 ohms across the primary of the coil itself. Another 1.3 -1.8 ohms is added with an external resistor.
The NAPA IC14s or IC14SB has a built-in primary resistance of 4 ohms last I checked.
A low resistance coil can give more spark potential but if run too long with no resistor at 14 volts, can burn out the points. Thus the reason why it gets used with an external resistor and a way to bypass it when cold starting. If you have breakerless, no extra resistor is usually needed.
The NAPA IC14s or IC14SB has a built-in primary resistance of 4 ohms last I checked.
A low resistance coil can give more spark potential but if run too long with no resistor at 14 volts, can burn out the points. Thus the reason why it gets used with an external resistor and a way to bypass it when cold starting. If you have breakerless, no extra resistor is usually needed.
Janicholson
Well-known Member
Rvirgil is correct. The volt meter will not load the circuit enough to see the running voltage. If you want to see that, turn the engine to close the points, then measure the applied voltage at the coil side of the ballast resistor. Jim
ces, you state "I've read that when a 12v conversion is done, the 6v coil isn't replaced for easier starts"
That can be true PROVIDED you add a series voltage dropping (12 to 6) external ballast resistor plus install/use a start ballast by pass system.
You cant simply use a 6 volt coil on a 12 volt tractor to achieve "easier starts" unless you add the external series voltage dropping resistor (or points burn prematurely and coil overheat) and to get those so called "easier starts" you have to install/use a by pass system that by passes the ballast while she's cranking so the coil gets unballasted battery voltage during that time.
So on a 12 volt tractor you can use EITHER a full true 12 volt coil OR ELSE a 6 volt coil plus a series voltage dropping (12 to 6) ballast. And if you want to improve cold weather starting you could use a 6 volt coil plus ballast BUT add a ballast while cranking by pass system.
Hope this helps
John T
That can be true PROVIDED you add a series voltage dropping (12 to 6) external ballast resistor plus install/use a start ballast by pass system.
You cant simply use a 6 volt coil on a 12 volt tractor to achieve "easier starts" unless you add the external series voltage dropping resistor (or points burn prematurely and coil overheat) and to get those so called "easier starts" you have to install/use a by pass system that by passes the ballast while she's cranking so the coil gets unballasted battery voltage during that time.
So on a 12 volt tractor you can use EITHER a full true 12 volt coil OR ELSE a 6 volt coil plus a series voltage dropping (12 to 6) ballast. And if you want to improve cold weather starting you could use a 6 volt coil plus ballast BUT add a ballast while cranking by pass system.
Hope this helps
John T
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