Tach, coil, Powerspark wiring
Posted: Tue Jul 20, 2021 8:13 pm
Hello all! I've near the end of my journey to get my S2 moving under its own power again. Fully rebuild drivetrain, all wiring ripped out, rewired everything by hand (no more bullets! 12 fuses!). etc. The engine is in and runs and the wiring is essentially complete and working well. However, I'm trying to puzzle out getting the tach working.
Part of the work was to convert from positive to negative ground. The generator's gone, an alternator is installed and is working fine. I took the tach apart and rewired it for negative ground. I also went from points to a Powerspark electronic ignition.
So, when the engine runs, I have these connections:
White wire from ignition switch to the tach where it makes a little loop then to the + side of the coil.
Red wire from electronic ignition to + side of the coil.
Black wire from electronic ignition to the - side of the coil.
In this configuration, the engine runs but the tach doesn't work. The tach does also have 12v going to a terminal on the back, and when I turn the key off, there's a slight click and the tach needle bounces slightly.
I tried looping the wire in the other direction behind the tach, no difference.
Some reading says that the white wire needs to go to the negative of the coil. Well, I tried that and surprise surprise, no spark so no running engine since the coil and hence the ignition never receive 12v on the positive side. More reading indicates that yes, the white wire should go to the + on the coil.
Doing some research, I've seen mention of powering the electronic ignition with its own dedicated 12V to cut down on tach wobble. That would mean...
White wire, ignition switch to tach to + side of the coil.
Red wire, from fusebox to electronic ignition
Black wire, from ground to electronic ignition
But that leaves nothing on the - side of the coil? Or should the black wire from the ignition go there instead of a direct ground? Or should it also get a direct ground?
I've also seen mention of grounding the case of the coil itself. Should that be done?
Finally, I have heard conflicting reports on whether the tach itself needs further modification (meaning, another bit of circuitry inside) to work with a Powerspark or similar electronic ignition? Maybe that's my problem all along? But I want to wire everything in the best way possible so I'm still trying to figure out the other questions.
Thanks folks!
Part of the work was to convert from positive to negative ground. The generator's gone, an alternator is installed and is working fine. I took the tach apart and rewired it for negative ground. I also went from points to a Powerspark electronic ignition.
So, when the engine runs, I have these connections:
White wire from ignition switch to the tach where it makes a little loop then to the + side of the coil.
Red wire from electronic ignition to + side of the coil.
Black wire from electronic ignition to the - side of the coil.
In this configuration, the engine runs but the tach doesn't work. The tach does also have 12v going to a terminal on the back, and when I turn the key off, there's a slight click and the tach needle bounces slightly.
I tried looping the wire in the other direction behind the tach, no difference.
Some reading says that the white wire needs to go to the negative of the coil. Well, I tried that and surprise surprise, no spark so no running engine since the coil and hence the ignition never receive 12v on the positive side. More reading indicates that yes, the white wire should go to the + on the coil.
Doing some research, I've seen mention of powering the electronic ignition with its own dedicated 12V to cut down on tach wobble. That would mean...
White wire, ignition switch to tach to + side of the coil.
Red wire, from fusebox to electronic ignition
Black wire, from ground to electronic ignition
But that leaves nothing on the - side of the coil? Or should the black wire from the ignition go there instead of a direct ground? Or should it also get a direct ground?
I've also seen mention of grounding the case of the coil itself. Should that be done?
Finally, I have heard conflicting reports on whether the tach itself needs further modification (meaning, another bit of circuitry inside) to work with a Powerspark or similar electronic ignition? Maybe that's my problem all along? But I want to wire everything in the best way possible so I'm still trying to figure out the other questions.
Thanks folks!