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Posted By : Graham Cowan, 06-Jun-2007, 08:28am
Hi all,
I had to replace an old coil as the screw fit HT lead connection had broken. This old coil had its terminals labelled SW (switch) and CB (circuit breaker).
The new coil has simply +ve and -ve labels. My question relates to the fact that my Herald is positive earth and looking at one of my car theory reference
books (see attached) it now suggests to me that in a positive earth situation the LT supply from coil to CB should be connected to the +ve terminal. The
coil is supplied in a clamp with its natural orientation being the -ve terminal battery side, I'm guessing this is just a default setup as most cars are
-ve earth? So, should I just rotate the coil 180 degrees and connect the ignition switch supply to the -ve terminal and LT to the +ve terminal. Oh and just
say someone had connected the +ve to the switch side and LT to the -ve side, has the coil been compromised!
Grateful for any replies.
Cheers,
Graham
New coil for positive earth Herald
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Posted By : Peter & Mick Lewis,
06-Jun-2007, 09:57am
Graham,,you are right +ve (cb)goes to ground via the points -ve (sw)is the ignition feed to the coil
its not uncommon for coil polarity to be reversed in error, it may run ok for ages then all sorts of odd stop start
faults start to cause unceremonial stoppages, later coils have inhibited terminals that control the connection.
reversed polarity on the primery coil does not allow enough potential difference to trigger the inductive secondary coil so
things get hot and spark voltage is way down ,, any short term reversal will not harm the coil. well something like that Peter
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Posted By : Graham Cowan, 06-Jun-2007,
10:48am
Peter,
Thanks a lot for your reply, most helpful.
It's little snippets of info just like this that would be useful in any 'how to' section. If such a section were to materialise may I suggest it
contains a 'what you need to be aware of if you have a +ve earth car' section.
Cheers,
Graham.