In Reply to: Re: 9N coil posted by Les Leach on April 28, 2018 at 12:17:58:
The ceramic external resistor to be used on 12-volr conversions using a 6-volt coli only sounds correct -see photo below. WE CAN"T STRESS THIS ENOUGH, but you MUST use the original ballast resistor in any set up using either a 6-volt coil or a 12-volt coil. Failure to have this in the circuit will cause circuit failure and damaged parts. Resistors are non-polarized so it doesn't matter which side is connected to whatever. They are however at a fixed value measured in OHMS (Resistance). Bruce and a few others did some testing a while ago on several ceramic resistors new, out of the box and got values readings all over the place. Don't assume that just because the package states "Rated at 1.2 OHMS" that it is. se your VOLT/OHM Meter and check for yourself.
Since it appears you have been trying to power this without the original Ballast Resistor in the circuit, like Bruce said, you probably have now fried the coil. You can test the coil with your VM METER but not a true test if good or bad -see BRUCE(VA)'s 75 Tips for more on that. You say 'at some point I want to eliminate the step-down(external) resistor and go to a 12V coil', well this may be that time. Since you now need to buy a new OEM Ballast Resistor and wire it in correctly, and if your 6-volt coil is fried, replace with a 12V coil, you can kill 2-birds, 1 stone. Your call, but you now have been given all the pertinent information needed so have at it and report back.
TYPICAL CERAMIC EXTRENAL RESISTOR: