Electrical: Microfarads of the Condenser?

[TWChamp]

Most cars use an ignition condenser in the range of .22 to .25 microfarads, but I couldn't find a listing for Studebakers. I bought two new Shurhit condensers from ebay the other day, and was surprised to find one measured .25, but the other only measures .16, which I'd consider out of tolerance.
Does anyone know what Studebaker used? Thanks, Tom

[gordr]

IIRC, 0.2 uF, +/- % is the typical value for an ignition condenser. So both of those are "close". Probably close enough to work OK. Old-time mechanic's manuals used to have a section illustrating how the build-up/pitting of the ignition points varied if the ignition condenser was under/over capacity for the coil being used.

[Bud]

Most ignition condensers have a capacity range of .19 uf to .22 uf. I've seen some condensers for Autolite distributors with capacitance as high as .26 uf. If you have a condenser with a capacitance of .16 uf, it is probably no good. Keep in mind that a condenser can show a capacitance that is within limits, but that doesn't necessarily mean that it's good. They also need to be tested for electrical leakage which is a test for insulation breakdown in the capacitor. That test requires a specialized cap tester that can supply the necessary voltage to test for insulation breakdown which modern cap testers can't do as most use an internal 9 volt battery for power. An ignition condenser has a working voltage rating of at least 400 volts and could be as high as 600 volts. Bud

[Hawkowner]

The old time machines like Sun had testers that would test and charge condensers it was great fun to charge one up an toss to some on or leave laying on bench for some one to pickup.Must say I bit.

Hawkowner

[bezhawk]

.22uf is what is stock. If you change the coil, then your requirements can change too. It depends on how your points wear. If metal is transfered to the power side of the points, or the ground side. Too much, and the metal is transfered to the + side, too little, and it is transfered to the ground side. Even wear and a slight greying of the points means you have it in the sweet spot.

[doofus]

Many decades ago i worked at a VW dealership. when doing tune up's the points were checked for condition and this determined whether or not the cond. got replaced. Doofus

[63 R2 Hawk]

The new condensers are made very cheaply in a foreign country and don't seem to have the quality of the original US made parts. The capacitance measurements vary and they don't seem to last as long as the ones we used to get back in "the day". That's why mine is converted to Pertronix. I haven't had to touch anything in the distributor for over 10 years now, except to change the rotor and check and lube the bushings. My old back sure likes not having to mess with points and condensers......

[christophe]

I've just checked this for myself. Sun charts gives 0.21 to 0.25 microfarads for all Studebakers.
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[kxet]

How is this measured?

[TWChamp]

Thanks for the Sun chart picture. I didn't even think to look at mine.

To measure the microfarads, go to ebay and buy a MASTECH MS8261 digital multimeter.
They only cost between $25 and $30 delivered, and they have many functions.
I bought mine to measure the cycles of the injectors on my 1999 Olds 3.8 engine.

[Bud]

Amazon has capacitor testers even cheaper usually around 15 to 20 bucks. The only problem with the new testers is they don't check for leakage which is important for ignition condensers as they have a working voltage between 400 and 600 volts and the new testers are powered with a 9 volt battery. The older style cap testers used for vacuum tube electronics is what is really needed to get an accurate test of ignition condensers as they can generate up to 600 volts to check for electrical leakage and insulation failure. Bud

[jclary]

I have enjoyed this thread. It is a very stark reminder that, although I have many years experience in working on "stuff"...USAF training on instrumentation, HVAC, electronics, mechanics, hydraulics, pneumatic systems, and even worked my way through college...there's tons of stuff I still don't know.

One thing I do know, as simple as our old vintage vehicles are, they can still make you feel like an absolute stammering fool. Like the time I worked for days trying to figure out why an engine would run great in my driveway, but sputter & stumble on the road. Only to find a bug wing in the little filter screen at the carburetor inlet fitting. It was choking gas flow like a check valve.

I have never lost any sleep worrying that my condenser has the wrong "Microfarad" rating. So thanks guys, now I can go to my local FLAPS and impress/confuse them even more when I ask for a Studebaker part...with a certain "microfarad." Should I make a video of the blank stare? Already, the younger guys at the store avoid eye contact when I come in.

[gordr]

John, you will probably never find the uF value of an ignition condenser marked on the box, or listed in the catalog. It's a "value" not a rating, as in the capacitance value is its essential characteristic, and why you even have one. "Ratings" can be described as measurements of the conditions under which it will work at it's described value. An ignition condenser might be rated at 600 volts DC, meaning it will sustain 600 volts DC across it without breaking down. That's the important rating, for that application. Capacitors are also rated for temperature coefficient, and self-inductance, among other things, and those properties would be crucial for a capacitor used in a tuned circuit in a radio or TV receiver.

A failed condenser might still read 0.22 uF on a test meter, but fail in use due to internal arcing from insulation breakdown.

You could probably buy an 0.22 uF, 1600 volt Mylar capacitor for under a buck, and stuff it into the can formerly occupied by the stock paper capacitor, and expect it to last nearly forever.

[RadioRoy]

Does anyone know if the capacitance value is different for 6 volt applications?

I could test one myself, but the box with electrical parts is buried and I have been too busy/lazy.

[christophe]

Does anyone know if the capacitance value is different for 6 volt applications?

I could test one myself, but the box with electrical parts is buried and I have been too busy/lazy.

Hi Roy,
As far as I know, The condensers are the same for 6 and 12 volts applications.
Besides, I dig up this chart as I just bought a multimeter with a capaciter function.
I ran a test on a brand new 0.27 microfarad condenser and my brand new multimeter gave me 0.246.
I'm just telling this to keep in mind that a certain margin seems to be tolerable.
On the other hand, an old condenser gave a whopping 0.349. This one is trash, I think.
In case this could be useful, here are the charts for V8 engines (courtesy of Bob Johnstone).
Nice week-end to all.