Posted by John T on December 08, 2022 at 06:47:59 from (174.239.82.163):
In Reply to: Round 2 it experiment posted by Geo-TH,In on December 08, 2022 at 04:47:08:
Mornin neighbor, what you found confirms my experience and understanding being one who farmed with those type of tractors and was at one time a used dealer which is as follows:
1) To use a 6 volt coil on a 12 volt tractor you need to drop the coil voltage to its 6 rated volts by adding a series voltage dropping ballast IE drop 6 Volts ACROSS the ballast leaving the remaining 6 Volts be dropped ACROSS a 6 volt coil WELL DUH.
2) A 50/50 Voltage divider (1/2 across coil 1/2 across ballast) would mean the coil and ballast would have the SAME resistance WELL DUH
3) I have seen many 6 volt coils with around 1.5 ohms resistance and many ignition ballast the same around 1.5 ohms WHICH (on a 12 volt tractor) IN SERIES IS 3 OHMS AND DROPS 1/2 ACROSS BALLAST AND REMAINING 1/2 ACROSS THE 6 VOLT COIL HOWEVER I have seen some 6 volt coils in the 1.25 to 1.8 ohms and some ballasts 1+ to almost 2 ohms !!!!!!!!! Of course different vehicles used different coils and ballast so their values would be a bit different MY 12 VOLTS AND 1.5 OHMS ARE APPROXIMATIONS not intended as perfect or accurate !!!!
4) In order to limit an ignition circuits LV primary current and to reduce premature points burning many Kettering ignition points circuits limited current to around 4 max amps WHICH IN A 12 VOLT TRACTOR WOULD MEAN YOU NEED A TOTAL OF 3 OHMS LV PRIMARY RESISTANCE (12/3 = 4) which is achieved if you had a 1.5 ohm coil and a 1.5 ohm ballast. Or on a 12 volt tractor use no ballast and a full true 12 volt rated 3 ohm coil .......... On a 6 volt tractor 6 Volts/1.5 ohms coil = that 4 amps
NOTE Sure when under charge the battery voltage may rise to 13+ to near 14 and a fully charged 12 volt battery at rest and stabilized is around 12.6 volts
5) A full true 12 volt coil has typically AROUND 3 ohms resistance while a typical 6 volt coil has AROUND 1.5 ohms. HOWEVER A coil labeled 12 volts FOR USE WITH BALLAST is in reality more like a 6 volt coil and needs the ballast LIKE IT SAYS or it will overheat and has AROUND 1.5 ohms resistance IE you need the ballast to reduce current and voltage
6) What some call a coil with an internal ballast DOES NOT ACTUALLY HAVE A DISCRETE STAND ALONE RESISTOR TUCKED AWAY INSIDE THE CAN but instead achieves its resistance by the winding alone..
Nuff said, Im sure I missed something so the other fine sparky gents can add more to this
John T Live in the RV from Panama City Beach, sunny and warm in the 70's yayyyyyyyyyyyyyyyyyy
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