The Ford Barn

Old Henry · 01-18-2026, 11:07 PM

I'm chasing an ignition problem so I checked the impedance of my coil.
Primary was .7 ohms. Close enough to what I thought should .75 to .81 ohms.
But the secondary coil impedance was only 5,500 ohms, half of what I thought should be 10,000 to 11,000 ohms. I don't know if that's off enough to cause my problem but I just ordered a new coil hoping it fixes it.

.................................................. .........

I just got the new coil in.
Primary impedance is .7 ohms.
Secondary is 8,500 ohms.

I had previous info saying that the primary should be 7.5 - 8.1 ohms and the secondary should be 10,000 - 11,000 ohms.
Neither of these secondary coils is 10,000 ohms.
I googled for the correct coil specs and found one source that said they should be 0.47 to 0.55 Ohms for the primary and 5,000 to 5,500 Ohms for the secondary.

How critical are these specs and is either of these coils too far out to work right or are both just fine?

corvette8n · 01-19-2026, 08:06 AM

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I’d say try either coil and see what the results are, make sure your condenser is also good.
Btw I miss seeing road trips posted by you, a few years back I visited Grand Canyon and Arches because of your videos.

01-18-2026, 11:07 PM	#1
Old Henry Senior Member Join Date: Oct 2010 Location: Orem, Utah Posts: 5,777	47 coil specs I'm chasing an ignition problem so I checked the impedance of my coil. Primary was .7 ohms. Close enough to what I thought should .75 to .81 ohms. But the secondary coil impedance was only 5,500 ohms, half of what I thought should be 10,000 to 11,000 ohms. I don't know if that's off enough to cause my problem but I just ordered a new coil hoping it fixes it. .................................................. ......... I just got the new coil in. Primary impedance is .7 ohms. Secondary is 8,500 ohms. I had previous info saying that the primary should be 7.5 - 8.1 ohms and the secondary should be 10,000 - 11,000 ohms. Neither of these secondary coils is 10,000 ohms. I googled for the correct coil specs and found one source that said they should be 0.47 to 0.55 Ohms for the primary and 5,000 to 5,500 Ohms for the secondary. How critical are these specs and is either of these coils too far out to work right or are both just fine? __________________ Prof. Henry (The Roaming Gnome) "It is good to have an end to journey toward; but it is the journey that matters, in the end.” *Ursula K. Le Guin in The Left Hand of Darkness

01-19-2026, 08:06 AM	#2
corvette8n Senior Member Join Date: Jul 2010 Location: 36 miles north of Albany NY Posts: 3,323	Re: 47 coil specs Sponsored Links (Register now to hide all advertisements) I’d say try either coil and see what the results are, make sure your condenser is also good. Btw I miss seeing road trips posted by you, a few years back I visited Grand Canyon and Arches because of your videos.