Measuring ignition coil primary resistance

I get asked this a lot, so here is a quick video on how to do it!

[jamesws]

Have learnt so much from these videos! Thanks for sharing!!

[onepairofhands]

your videos are really helpful - thanks for posting

[Andyslandys]

So helpful! what are the odds of five coils being burnt out and sure enough thanks to your video I finally diagnosed that all! my coils are burnt out, 2 are new, never used!!!! because none of them have a secondary resistance, I'd been going mad trying different multimeters finally figured out that the only setting you should use is the one that beeps despite the instructions on the Klein meter I shelled out for you should definitely just use the continuity one it'll give you the reading you need, I've been trying everything else assuming I would get a more accurate reading, that is not the case!

[peterzumstein]

Great video and well explained, thank you. Still one question: what happens, if you use a 1.5 Ohm coil on a non-ballast breaker-point system of the mid-sixties where a 3 Ohm coil should be used?

[MCCZPL]

Great information. Maybe it would be usefull to say what spart plug gap you recommend for each application as well? 0.025 for point distributor and 0.035 for electronic one? (as most sources say, or do you have other opinion based on your experience?)

[maxxsmaxx]

Wet coils use oil in it to Desipate heat towards the shell. This is good featture to keep the coil cool and maintain effencey unlike dry coils.

[paulstevenson]

Very good advise brings me back in time when I was a home tune man amazing the amount of times incorrect coils been fitted and ballast resisters being missing and cold start feeds not there when cranking, can I ask why you don't scope anything to look at ignition rotor air gap or ht kvs interesting to see you only use lambda don't you use a four gas

[markleatherland]

Hi AC - useful info again Thanks. You showed a coil damaged by running too big a spark plug gap for a ballast system. Is there any issue or consequences of running too small a gap with an electronic system i.e. 65DM and 0.9 coil

I need to check mine as I'm not sure I realised or read the right info when I fitted my kit car with 65DM/0.9coil from an MG Metro- cheers, Mark

(Note - I've also just changed my air filter after watching one of your on the road sessions where you said the filter fitted was no good which was the same as the one I had)

[MiniMattTV]

Excellent information. Just for clarity, if you are fitting an electronic points replacement kit, would you stick with the same coil as for actual points? Most adverts say no other modification necessary. Do these kits change your plug gap recommendations also? Cheers

[alhamedi]

I subscribed channel deserve it.
Clear clean organized professional work with passion.
What we do in the past all wrong because when coil faulty they replaced any other coil without checking all this information.
How I know the right coil for my classic car.
Best regards,

[davelinkson]

My 1972 MGB (non ballasted)is having some problems with coughing and spluttering and cutting out when hot in stop start traffic, am using CSI electronic dissy with Lucas sport coil (gold) oil filled, am thinking of replacing with a dry coil to your instruction in the video. Thanks.

[herbnalis]

All new cheapy multi meters are shipped with the 9 volt battery not fully connected. The plug is pushed on 1 terminal & just touching on the 2 terminal. That's why it wont zero when probes connected. It's a good idea to fit a new 9 volt battery as well.

[johnnymees]

Great video, I'm looking for a small coil to replace The standard 12 volt 'Lucas' type . Must be 3.5 or more ohm primary resistance Any ideas ?

[bernardwarr]

Just to add to your excellent information. MSD in the US do a coil with primary resistance of .7 OMS and a ballast resistor of .8 OMS as a high performance kit, for points cars. What’s your thoughts on that?

[Nudnik]

Coils when hot often change dramatically in Ohms.

[kkaplin]

hello and thanks for the video.
i have a coil with primary resistance that tests within specs but a secondary resistance that tests a bit high. (secondary range is supposed to be 2.4k-3.5k, coil is testing at 4.37k). is there any problem with running this coil? what impact might it have?

[nicholaskennedy]

Hi AC Dodd,

I've been thoroughly enjoying watching your videos lately.

I needed some clarification from yourself regarding coils - I have fitted the Powerspark 65DM4 distributor, with High energy coil (0.7/0.8 ohms, part number replaces DLB 198) and silicone leads. I have seen on the powerspark website and the video with Twin-cam that it should be the correct rating coil.

However, on one of the mini forum threads, you have advised somebody to use the 1.5ohm coil instead, as using coils with lower resistance causes premature module failure and reduced part throttle torque.

Would you be able to advise which information is correct? Could you have just meant if the plug gaps were increased, putting wear on the coil? I am by no means disputing your excellent work and advice, but I just want to know what I have fitted is correct before I start the engine

Regards, Nick

[amidzlad]

Hi A.C. My Ignition Coils Primary Resistance is 0.8Ohm (I have a 65D Distributor Fitted).
The Secondary Winding Resistance is something like 4.6k. What's considered an acceptable Secondary Winding Resistance.? Is the Secondary Winding Resistance Value anything to be Concerned about.? I've had 2 Viper Dry Coils Fail on me Within a year, so have gone back to the Tradional Oil Filled Type for now.

[anomalous]

Does the coil have to be checked disconnected from the car?

[tonywood]

Which would be for a 1980 998cc mini van with electronic ignition AC?