Do the instructions say negative terminal? I don't believe there is one on a coil.
The red leads are constant 12v (+). The black (front) and blk/green (rear) are the signal leads from the ignition controller (+). The coils ground (-) through the mounting bolts.
Steve, this is exactly what I've seen yesterday when I measured the terminals Instructions of the tach show the green connected to the negative of the coil and the tach's black(-) wire connected to the ground. My Drag Specialties adapter has the 2 black wires that I will connect reluctantly to the black of the coils. And I will get power for the tach from the red(+)of the coils.
More over, looking on the bottom of the coils I noticed that the red wires go to a green base on the coil and black wires go to a black base on the coil.
I will keep you posted later on. Thanks to all for the ideeas and help with this.
Update: hooked up all as I mentioned. Ignition key ON, tach does initial 0 to 8K and back to 0. Light tach ON. Monitor voltage from good ground to one of the black wires from coil 12V. Start engine and monitor the voltage 13V. Tach stays at 0. And I ran out of ideeas.
I am now contemplating removing the gas tank for the first time and look for a dedicated terminal for tach from harness if it is there.
I just don't get it. Where is the negative to coil? They are all positives?
Or get a wirring diagram and and try to understand how it works.
Are you sure the tach works?
What name or brand of tach do you have?
It sounded like you have it hooked up some what right the first time.
Red to hot wire.
Ground the tach out to frame or a good ground spot.
Then your signal wire should go to coil.
2008 Vulcan 1500 Classic fi
Last edited by C00lCountry; 11-10-2012 at 10:12 AM.
It is a new tach and it does what is supposed to: it does initial on power ON, tells me it is OK. This is a 2011 Kawa Vulcan 900 Custom special eddition.
I just think this is a new type of coil where the coil is getting the minus from the ground via the frame and it has 2 positives to each coil. But why? This is the big question and without a schematic diagram can not be answered.
I thought I new them all after riding for 40 yr.
Sure, the adapter is single fire made by Drag specialities (sealed from ebay).
The description is Harley single fire adapter but of course should work with all tachs.
The problem is where can I connect the minus of the adapter. In any case now I know not to the coil because there is none. There is continuity between all 4 coil wires and they are all positive. Why? This it the 64K $ question.
If you have wired up as I specified, the tach should work. If not, the adapter is bad or the tach.
There are NO negative or ground readings to be had on your coils.
If key on and engine NOT running, both sides of coil WILL read 12v. That is normal.