Today's Message Index:
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1. 12:24 PM - I'm Confused (Tim Juhl)
2. 01:11 PM - Re: I'm Confused (Rob Turk)
Message 1
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On the standard ignition modules I connected the shield side of my magneto wire
to ground and the spade to the mag switch. In operation, the switch would ground
the wire from the spade when off, open when operating.
I have yet to run this engine but in doing some preliminary checks, I find that
when I use a continuity tester on the spade that the mag switch connects to I
get continuity to ground, even when nothing else is attached to it.
That doesn't seem right to me so I assume I am missing something here. Hopefully
one of you can enlighten me.
Tim
--------
______________
CFII
Champ L16A flying
Zodiac XL - Jabiru 3300A
Almost done! It'll fly in spring!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=444573#444573
Message 2
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| Subject: | Re: I'm Confused |
Tim,
The Jabiru engine does not have 'magnetos'. It has ignition coils. The
ignition coils have two windings. Both windings have one end connected
to engine ground through the iron core.
The high-tension (HT) winding generates the spark when a magnet on the
flywheel passes the coil. The HT winding terminates in the HT lead to
the distributor.
The second, low-impedance winding is designed to mess up the pulse
generation in the HT winding when short-circuited to ground. It makes
the magnetic field collapse and prevents the energy build up for a
spark. The low-impedance winding terminates in the spade.
When you use an Ohm meter, you should measure about 5 - 8 kOhm between
the HT lead and engine ground. You should also measure very low
resistance to ground on the spade terminal. This is only 1.6 - 2.5 Ohm,
so a simple continuity tester will show it as a short to ground.
Download the engine maintenance manual (JEM0002-5) and find the
Electrical System Specifications. It has a table showing the expected
resistances for each coil type.
From what you described, all is well.
Rob
On 7/8/2015 9:23 PM, Tim Juhl wrote:
>
> On the standard ignition modules I connected the shield side of my magneto wire
to ground and the spade to the mag switch. In operation, the switch would
ground the wire from the spade when off, open when operating.
>
> I have yet to run this engine but in doing some preliminary checks, I find that
when I use a continuity tester on the spade that the mag switch connects to
I get continuity to ground, even when nothing else is attached to it.
>
> That doesn't seem right to me so I assume I am missing something here. Hopefully
one of you can enlighten me.
>
> Tim
>
> --------
> ______________
> CFII
> Champ L16A flying
> Zodiac XL - Jabiru 3300A
> Almost done! It'll fly in spring!
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=444573#444573
>
>
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