Capaciter value and mf Meter

[Al 29Tudor]

Hello Barners,
After reading Ron Ehrenhofer's article in the Model "A" News, on capacitors, I bought two of the microfarad meters, one for our club tool box and one for home. Capacitors are always mystery components and suspect when an engine won't run. I tested two used and two new capacitors and they were all 0.23 – 0.24mf. They are the pigtail type installed on the upper plate. The article references a letter from Ford stating the capacitance should be 0.30mf.
Has anyone tested an original type capacitor that mounts in the base of the distributor? And what reading did you get?
I also intend testing one after returning from a ride when it is hot to see what change if any occurs.
Thanks for your comments and advice.
Al Leach

[Brianfrench65]

I sure did. .243 +/- .01

[Tom Wesenberg]

That .3 might have been a mistake in the original letter from Ford. Recently Vince posted the correct reading as .23uf or close to that. Anything in the .22uf to .27uf range will work fine. That's where most of the capacitors I check are reading.

When I first saw the .3uf in the Ford letter I thought that seem a little high, because back in the 60's most every car's capacitor was listed as .22uf to .25uf.

[P.S.]

That value chosen was based on the physical size of the wax/paper rolled capacitors available at the time, and what would fit inside the metal can for the automotive condensers. The next size up is .5 uF, but it is nearly twice the physical size for the same voltage rating.

Any capacitor value up to and including 1 uF will work fine for an automotive ignition system.

What you have to watch, especially with the modern solid state capacitor testers that use square wave output, is capacitors that are leaky will read higher in value. For example, a .25 uF capacitor that has 500K of leakage will read somewhere in the .35 uF range. So, always start with an ohm measurement before you even try to test uF. If the leakage is infinity (display shows nothing, just like when the leads are not touching anything), then your capacitance measurement will be fairly accurate. Otherwise, forget it.

[BILL WILLIAMSON]

FUNNY!! "mf meter" in the title, made me think that someone wuz cussing his meter! +*@%$$^$@$%+*^
Bill W.

[wrndln]

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I have a Ford script condenser that I measured with my newly purchased capacitance meter. It measures .234 uF which sounds right on. I am amazed the capacitor is still good after many years, but probably not used all those years.
Rusty Nelson

[henry's 31]

We had a shop meeting last Friday (yes on the first of January!) We all tested the condensor and they were at least .22 to .24. A great tool to have around.

[Mike V. Florida]

Everybody must also keep in mind that a static reading of the cap outside the car on a table will tell you if it's 100% bad, but will not tell you if it's 100% good. Voltage and heat are two factors that the tabletop test cannot test but will make the cap not usable in the car with it running.