[s-cars] Hesitation -- please help

[Paul Gailus]

Sorry, Bill, I guess I wasn't too clear about the suggested coil measurement
details.
The 27 volts is intended for measuring the coil's high voltage output
circuit
(consisting of the "secondary" winding and internal series diode).
The yellow and black wires which go to the coil's input circuit ("primary"
winding)
are not involved in this particular measurement. Their resistance can be
measured
directly with a meter and without any extra applied voltage, just like we
did when
we found your shorted coil.

The first step in measing the coil output circuit is to pull off the black
spark plug
connector from the coil.
The meter should be set to measure DC current, with the red test lead
connected
to the meter's "A" (amps) terminal if it has one.
You want the coil secondary circuit, the battery, and the meter all in a
series
connection.
So first tie the negative side of the battery to the laminated steel core.
Tie the red (positive) lead of the meter to the positive side of the
battery.
Then touch the black (negative) lead of the meter to the coil high voltage
output terminal. You should read somewhere around 5 milliamps (+- a few
milliamps).
The exact reading is not important.
If you reverse the battery polarity, then you should measure essentially no
current
because of the internal diode that's in series with the coil output circuit.

By the way, I'd be a little careful not to accidently put the meter directly
across
the battery while the meter is set to measure current. The meter will have
some
protection and fusing and the 9V batteries have limited current, but I'd
still avoid it.

How did I get the ~5 milliamp number? I just measured it on a new coil ;-)

You're right Bill, I really need to do S-Fest. And both of my S-cars are
running
(last time I checked). It's been way too long since I was at a real S-car
event
(2001Nationals) and you guys have been having way too much fun.

-Paul

----- Original Message -----
From: Bill Mahoney
> Thanks Paul for this great explanation and seemingly simple coil testing
> procedure.
> I'm going to try this on my five old coils.  If I can find the bad one, it
> would be great to have four spares.
> And please forgive my stupid question/s, but just to clarify in my
> lamebrain:
> I would connect these 27Volts to the coil wires.
> Then -
> Connect one end of the meter to the coil output and the other to the
> laminated steel core and get a reading around 5 milliamps OR zero, then
> reverse the connections and expect to get the inverse reading?
> Also, how is this 5 milliamp number arrived at I wonder?
> And BTW,... anyone with TWO S cars is a big time candidate for the Sfest
> pilgrimage.  Heck at least one of them should be running;)
> Cheer's
> Bill ~meggered out~ M

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