Topic: Coil Resistance Check Question

[Popwood]

I'm following the FAQ about how to check coil resistance. I'm checking my '75 750K set up stock. I'm getting a good 5 ohm reading on primaries, but getting no reading on secondaries. The FAQ isn't quite clear on which two ignition wires to insert probe into to make the test. I've tried various combinations of wires but still nothing. The FAQ does reference two wires that spark at the same time. I'm thinking that would be 1/4 and 2/3 with one of those combinations being a "wasted spark." But needless to say I could certainly be wrong. The spark plug caps are off. Am I missing something here?

[05c50]

You're right, it is 1/4, 2/3. If you're using a digital ohm meter, turn the knob a notch or two. That should give you the reading you're looking for.

............Paul

[Frostyboy]

You're right, it is 1/4, 2/3. If you're using a digital ohm meter, turn the knob a notch or two. That should give you the reading you're looking for.

............Paul

+1.
Depends if your meter is auto ranging. You need to select kΩ. I just measured one of mine with the caps off & it measures 14.8kΩ.

[Popwood]

Thanks, guys, I'll try it. I had the digital meter set to 200, which I thought would be right for anything under that setting. I'll flip around tomorrow and see what I can get.

[Bodi]

You must measure from one spark wire on a coil to the other spark wire on the same coil, not from one to ground. You should have "infinite" resistance from any spark wire to ground.
Also check your plug cap resistances. The original caps were 5K I think, maybe 10K. The resistor can fail and give a very high or infinite reading and although such caps will usually just arc inside and work somewhat, they should be replaced.

[Popwood]

You must measure from one spark wire on a coil to the other spark wire on the same coil, not from one to ground. You should have "infinite" resistance from any spark wire to ground.
Also check your plug cap resistances. The original caps were 5K I think, maybe 10K. The resistor can fail and give a very high or infinite reading and although such caps will usually just arc inside and work somewhat, they should be replaced.

Thanks, Bodi, the caps are 5K and look to be in good shape (no corrosion on metal connections) but I'll check them as well. I did check the 1/4 and 2/3 wires before leaving for work this morning, using a different ohm setting on the multimeter and both sets came up right on 15.