What is the difference btw primary and secondary resistance?

[jdumont]

I suspect I have a bad spark plug wire. When i check the wire from one side to the other i get 11.15 ohms. How am I supposed to be checking this thing. I see other posts about 3.5 ohm and 30,000 ohm primary and secondary resistance. Is there a write up on this anywhere?
Thanks in advance

[Black_peter]

The ignition coil has two coils really. A primary that 12 volts runs through. And a secondary the one connected to the spark plug. So it works similar to a transformer in that the secondary coil has about 2K times more wire in it. So the 12 volts gets amplified to 25,000 volts. The side effect (because Ohm tells us everything has to match) is that the current is much much lower. Basically it creates static electricity type voltage. When you rub your feet on the carpet you are building up thousands of volts, it is just at a minute current. That is why you can't kill yourself holding a spark plug but it hurts like a SOB! 25,000 volts with anything more than 1/2 amp will put you right in a grave..

So you have on the coil two measurements to make. The Primary (low resistance) where the two wires connect from the CDI. And the secondary (high resistance) where the spark plugs connect. Unlike a car coil where one end of the secondary is grounded, in the Kat both ends of the coil go to a spark plug. So you can measure from one spark plug boot to the other and subtract a bit for the wires (maybe 5000 ohms).

Savvy?

Getting back to the spark plug wire, I thought Katana wires were more like 5000 ohms/foot..
It might take some searching but it was in the forum somewhere...

[jdumont]

Ok i guess that makes sense. I wish i didnt take the wire out of the coil now because im sure i broke it. Ill test the other side now.... test the other coil from end of spark plug wire to the other one and it was an open. How is that possible....

[Newbie2it]

JD, there should have been two wedge peices on each side of the coil wires, Its part of the clip I mentioned about in the other post, If you cut back the wire, its going to be a little tough to get it back in, but its do-able. I've replaced my wires before. As long as you still have the two peices that attach to the wire, you just need to pinch them together to go back into the coil. Once its in the coil, the little nubs on the inside will make a new home into the outer shell of the wire to hold it firmly in place. If you need help, lemme know. Its just hard to get them back in at first since the original dent that the clip fit into is now gone.

[Black_peter]

Newbie described that really well.

If you were reading an "open" from one wire to the next either that coil is broken, or the boot/wire/connections are bad.
Or maybe your meter didn't auto range.

The spark plug boots disassemble really easily. You can trim a bit of the wire and reassemble them..