More questions for Tom Wesenberg

[ct]

Hi all,
Tom, I've been trying to trouble shoot ignition problems with my '28 tourer and found your response to a question relating to condenser testing. I've discovered that my multi-meter can measure capacitance (only in the nF - nanofarad range) so I tested a new condenser out of the circuit. The result was 216.6 nF. This was the same whether I placed the red probe on the case or the terminal.

Conversion to mF - millifarads (the unit used in your response) gives me a reading of 0.0002166 mF, conversion to uF - microfarads gives me 0.2166 uF. The number is nearer your readings but not the unit of measure. Does this mean the condenser is faulty?
Can you set me straight on 1. polarity, 2. units, 3. minimum acceptable reading.

Thanks in advance for all responses.

[Tom Wesenberg]

I would only use a correct capacitor tester to check your capacitor. You could use your multimeter to check for a shorted capacitor. What are you ignition symptoms that made you check the capacitor? An ignition system with a bad capacitor will still make your hand twitch, but the spark will be very weak. When I installed a bad condenser in my Model A I couldn't drive any faster than about 20 MPH due to the weak spark.

[Mike V. Florida]

Can you set me straight on 1. polarity, 2. units, 3. minimum acceptable reading.

1) polarity in the condensers used in the A have no set polarity.
2) Makes no difference in how you read the meter. Example, is there a difference between 60 miles per hhour or 1 mile per minute?
3) There is no cast in stone minimum reading. .21 might work fine, might not.
More than a few members here have tested the caps at .22 to .24. Your .2166 would round up to .22 and is within what others have read.

One more thing, the reading on the meter can tell you if a condenser is bad for sure. A short or an open or even a wild reading, but with a "good" reading you can still have a condenser that will not work right installed in a car and under operating conditions.

[ct]

Hi Tom and thanks,
Initial problem was loss of power most noticeable at lower revs. and sooty fouling of plugs (like running rich). I have found and corrected some potential causes resulting in improved performance, however when I placed a spark tester between the distributor and plugs (new ones) it showed intermittent breaks in an otherwise strong, steady arc stream.
I have since found a possible intermittent short between the conduit from the generator (I'm actually running an alternator) to the terminal box pole with cable going to coil. I currently have a good arc but will check again in the morning before going on a club run.
I have a tester like the one you used on order.

Mike V, thanks also for your clarifications.
My dilemma with the units is that they don't readily convert to Toms.
Note that Tom used mF and I used nF. If I convert to mF I get 0.00022 compared to his 0.23 and 0.27. This is a significant difference.

Thank you both for taking the time to respond.

[Mitch//pa]

You'll get a better idea of the flow of spark into the cap if you place the spark tester in series of the coil wire instead of the plugs... This will be a more rapid and steady flash unless you have an issue. Checking them at the plugs is good for diagnosing a misfire or cylinder drop out. Condenser wise I keep a few good modern short proof ones on hand and never test them, as its to subjective...kind of like using a vacuum gauge

[ct]

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Thanks Mitch.
I have had good spark when tested at that location, but I will check again as the test at the plugs has yielded variable results.