[Shop-talk] Electrical Testing

[Randall]

> I have a few lying around and 
> wondering if I can test them somehow ?? 

How antique is your antique?  Is it Kettering style or does it use a
vibrator coil ala Model T ?  Or a magneto coil ? Etc...

Assuming it is Kettering style, by far the best test, IMO, is to put it on a
car and see how well it runs under load (take a test drive).  But there are
some simple bench tests that give perhaps 75% confidence that the coil is
good.  Used to be a nice blow-by-blow sequence on Mossmotors.com but I can't
find it at the moment.  

Basically you start by checking the resistance between the two side
terminals (which for an antique should be around 3 ohms although 1.5 ohms
started being common in the 1960's), and the resistance between the between
either side terminal and the center terminal (which should be around
10,000-15,000 ohms).  Also check the resistance between any terminal and the
case (which should be at least 20 megohms if you keep your fingers away).

Then set up a spark gap of some sort (eg old spark plug) between the center
terminal and either side terminal, and connect a 12v source across the side
terminals.  When you pull a wire off, you should see a spark.

> Can I simply put a lead of an electrical tester 
> on each cable and read the meter ??

Depends a lot on the charger as to what you will read (if anything).  Most
'dumb' chargers are going to look like 18 volts or even higher; some
combinations of charger & digital meter will give readings that jump all
over the place (the chargers output actually varies between 18+ volts and
zero).  Many 'smart' chargers won't put out anything at all until they see a
battery connected.  Again the easiest/best test IMO is to hook them to a
battery and see if they charge it (which you can judge by measuring current
and voltage).

-- Randall