Testing plug wire with OHM meter. I don't understand the readings

will e · Oct 28, 2024

I used two different meters on the same coil wire. It's about a 18" long. One meter I tried at settings that read 200, 2000 and 20K. The digital meter read as follows:
200 = 1.9
2000 = 63
20K = .17

I also tried it with a radioshack 'pocket meter'. There is only one setting which reads K and the Omega. This produced a value of 97.

So, I am confused by these readings. Anyone with more electronic skill have some insight. I looked around on the web and tried copilot and wasn't able to get a satisfactory answer.

Steve McMahan · Oct 28, 2024

I’m not sure this will help, but here is a video of testing spark plug wires with a VOM:

Hope it gets you what you’re needing. Good luck.

Bentworker · Oct 28, 2024

1) how old is the battery in your meter?
2) what condition is your meter in?
3) want to blow money on a new meter?

will e · Oct 28, 2024

1) new batteries
2} seems fine
3} Not really, I have two meters now.

I am just trying to understand what the readings mean. For example, when set at 200, is that the max or a factor or a bit of both? Do I take the value and multiply it by 200? It's interesting to me that 200 and 20K are 'similar' but 2000 isn't.
And what does the 97 mean in comparison? If it is self adjusting is that 97 Ohms of resistance?

I have a ballast on order as part of my effort to throw parts at a problem. When that arrives I should have a known 'baseline' to use for comparison purposes.

will e · Oct 28, 2024

At 11:48 it solves the riddle!

You use the lowest setting that doesn't return a value of 1 or LO. So in my case I use the 200 setting.

rvrtrash · Oct 29, 2024

As mentioned, you would use the lowest setting, so 1.9 ohms. Here's a problem you may run in to. Digital meters use low current to measure ohms, so if you have a multi-strand wire, like a spark plug wire, and all the strands except one are broken, it will measure the resistance across the remaining strand and show low resistance, implying a good wire. Under load, there will be more voltage drop, since not all strands are carrying current, and your system won't function. An analog meter or a "megger" are better tools for measuring this. Short story, if you suspect you have a problem with spark plug wires, and only have a digital meter, just buy new spark plug wires.

Bobby · Oct 29, 2024

rvrtrash said:
As mentioned, you would use the lowest setting, so 1.9 ohms. Here's a problem you may run in to. Digital meters use low current to measure ohms, so if you have a multi-strand wire, like a spark plug wire, and all the strands except one are broken, it will measure the resistance across the remaining strand and show low resistance, implying a good wire. Under load, there will be more voltage drop, since not all strands are carrying current, and your system won't function. An analog meter or a "megger" are better tools for measuring this. Short story, if you suspect you have a problem with spark plug wires, and only have a digital meter, just buy new spark plug wires.

Agreed. If in doubt, replace the whole set. You can go the cheapie (Autozone) way or buy low resistance wires by MSD and also, while you're at it, new tritium plugs......unless you're going concours.

Testing plug wire with OHM meter. I don't understand the readings

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