There is no external second connection for the secondary winding, it is
internally connected to the CB or -ve terminal, not the coil body.
With a 12v coil (i.e. chrome bumper cars) you should see 12v on the coil SW
or +ve, a white wire, with the ignition on, whether the points are open or
closed (maybe a slight drop when they are closed).
On the coil CB or -ve you should see 12v with the points open and a ground
with them closed (ignition on not cranking). Note that absence of 12v is
not necessarily a ground, you need to connect the other side of your meter
or test-lamp to a 12v supply to detect a ground.
With a 6v coil (rubber bumper) you should see 12v on the coil +ve, two
white/light green wires, with the points open and about 6v or so with them
closed. This is with the ignition on. When cranking this will rise to full
battery voltage, which under normal circumstances will be about 10v,
regardless of whether the points are open or closed.
On the 6v coil -ve the conditions are the same as for the 12v coil i.e. with
the ignition on you see 12v with points open and a ground with them closed.
This doesn't agree with some of what Les says I know, but the voltage you
see on the coil +ve of a rubber bumper car, unless cranking, depends on
whether the points are open are closed. This is because the coil +ve is
effectively in the middle of a potential divider created by the coil
resistance and the loom ballast resistance: Points open - no current - no
volt-drops - you measure the supply voltage at all points along the
potential divider. Points closed - current flowing - volt drops in the
'arms' of the divider - different voltages with respect to ground at
different points along the divider.
If the voltage on the coil +ve or either type of coil drops significantly
from what is stated, like to zero, when the points are closed you have a bad
connection back towards the fusebox/ignition switch, no voltage at any time
with the ignition on is a disconnection.
If both coil terminals on either type of coil stay at 12v whether the points
are open or closed there is a disconnection towards the points.
If both coil CB or -ve stays at ground, and the 6v coil +ve stays at 6v,
when the points are open the points wire is grounding or the points, coil
wire and condenser wire have been incorrectly assembled.
If the SW or +ve terminals of either coil stays at 12v all the time, and the
CB or -ve terminal switches between ground and open circuit as the points
close and open, the coil primary is open-circuit.
If a 12v coil primary is short-circuit you will fry the wiring between
points, coil, ignition switch and solenoid while the points are closed. If
a 6v coil with a short-circuit primary has the correct loom ballast then no
damage will occur, except possibly to the points. The normal primary
resistance of a standard 12v coil is about 3 ohms, for a sport coil can be
about 2.4 ohms, and for a standard 6v coil is about 1.5 ohms. A 6v coil
used in a 12v system without an external ballast resistance will overheat
and possibly burn the points.
----- Original Message -----
From: <Menno.Meijer@ict.nl>
To: <mgs@autox.team.net>
Sent: Tuesday, August 12, 2003 9:36 AM
Subject: Coil question
> - Where can I find the second terminal of the secondary winding?
>
> My second question ...
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