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Monza ignition coils

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MGGGG View Drop Down
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    Posted: 06 Dec 2018 at 15:44
just bought a couple of new ‘ai’ ignition coils for my 1984 monza, off eBay, came without any instructions! The original coils (nippondenso) have two wires, one coming out of each end. These coils have two spade terminals both of which are on the same end. There is nothing on the coils to indicate which is which! On the originals the orange lead from each coil connect together, the black leads go into the loom and presumably end up in the CB’s. Has anybody fitted these coils? Does anyone know which of the two spade terminals connect the coils together? (For the record these coils were £19.50 each, so hopefully they will work ok)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris950s Quote  Post ReplyReply Direct Link To This Post Posted: 06 Dec 2018 at 16:16
The wire that links the two coils is white on the wiring diagrams, I suspect that someone has altered the wiring at some time. You say it has a CB so I assume it is the  Monza II and not the earlier one with electronic ignition. There should be a white wire supplying power from the ignition switch via the kill switch that attaches to the RH coil and this terminal is linked to the LH coil with a second white wire. The wires from the contact breakers connect to the other terminal on each coil are red to the RH coil and green to the LH coil. 

I hope this helps
Chris and Karen - Essex
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 06 Dec 2018 at 16:27
Is there any marking on the coils such as a + or -?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote iansoady Quote  Post ReplyReply Direct Link To This Post Posted: 07 Dec 2018 at 10:09
I believe that although there is a "correct" way round to connect coils they will still work the "wrong" way round - but the HT generated will be the opposite polarity to that intended.

Essentially the LT circuit is between the 2 Lucars; the HT is between the HT cable terminal and earth.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 07 Dec 2018 at 10:40
I'm sure all the normal old style coils had some markings for the primary.

But there are coils designed for CDI ignition which may not have this. They may also have a very low primary resistance, so are not OK to use with points.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote c13pep Quote  Post ReplyReply Direct Link To This Post Posted: 07 Dec 2018 at 10:42
Originally posted by Brian UK Brian UK wrote:

I'm sure all the normal old style coils had some markings for the primary.

But there are coils designed for CDI ignition which may not have this. They may also have a very low primary resistance, so are not OK to use with points.




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Post Options Post Options   Thanks (0) Thanks(0)   Quote MGGGG Quote  Post ReplyReply Direct Link To This Post Posted: 07 Dec 2018 at 12:02
Thanks for the response lads, brilliant. Your right about the white wire Brian, that’s the one that goes into the loom, but the wire out of the nippondenso coil that connects into the white wire is orange and that is moulded into the coils - so the wiring loom is standard. If, as it appears, I can’t damage anything by connecting up the wrong way (a 50-50 chance) I can just try it? My monza is the points model, if the coil is for an electronic model can I cause any damage trying it? By the way, for the record I just found the identical coil on M&P site for £16.39! based on the principal you get what you pay for (been quoted £75 each for suitable coils) hope these are OK!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 07 Dec 2018 at 12:49
Any generic 3 - 4 ohm ignition coil will work. You don't always get what you pay for.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote MGGGG Quote  Post ReplyReply Direct Link To This Post Posted: 07 Dec 2018 at 14:04
Thanks again Brian, and all, I’ll give it a whirl, and let you know how I get on.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris950s Quote  Post ReplyReply Direct Link To This Post Posted: 07 Dec 2018 at 15:31
Originally posted by MGGGG MGGGG wrote:

Your right about the white wire Brian
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Chris and Karen - Essex
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 07 Dec 2018 at 22:53
Obviously passed his telepathy exams.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MGGGG Quote  Post ReplyReply Direct Link To This Post Posted: 08 Dec 2018 at 17:47
Had a few hours to go out to play.. fitted the coils and all appears to be well! Both plugs sparking great. For the record one of the two spade terminals has a small pvc shroud at its base - this is the + terminal. I connected them into the white wire which I think goes to the ignition. Just remains to road test now, and hopefully won’t go onto one cylinder after 20 miles or so. Thanks again.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 08 Dec 2018 at 22:53
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nab301 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Dec 2018 at 23:42
Originally posted by iansoady iansoady wrote:

I believe that although there is a "correct" way round to connect coils they will still work the "wrong" way round - but the HT generated will be the opposite polarity to that intended.


I remember as teenagers this question used to come up with fellow em zedders when we were replacing poor quality east German ignition coils.  It was suggested at the time that the spark plug might wear more quickly .. Googling the question suggests something similar.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: Yesterday at 09:20
The spark will erode one electrode more according to the polarity. So reverse the polarity and the other electrode will erode more.

In practice, it makes little difference as long as you check the plugs and gap them regularly.
Brian.

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