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Ignition coil resistor


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I fit NGKAPR6FS which are I understand standard ford fitment to Sierra pintos.

These are resistor plugs.

The resistor acts to supress electrical noise messing up the radio.

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I have the same potential challenge, the leads to/from the coil supressor are in a bad state. I have done a bit of research on this subject. There are two conflated things in some of the previous posts here. The two things are (1) a Ballast Resistor and (2) a Supressor. There is a nice piece of explanation on the Burton site that covers (1).

https://www.burtonpower.com/tuning-guides/tuning-guide-pages/ignition-systems.html

Reading this I do not believe the unit in your picture is a Ballast Resistor because the ignition on my Sierra is ESCII, i.e has no points. In any case this can be verified by measuring the voltage at the feed (positive input) of the coil, as explained by Burton. This then leaves the option (2) it's most probably a suppressor. What's that? I here you ask. Notice the markings on the unit, it has a marking for capacitance in Micro Farads (2.2 I believe and a resistance of 73 ohms). When the coil is producing high voltage ignition sparks some of the high voltage can get generated in the coil input circuit. Normally this should only be 12 volts. So the capacitator absorbs sudden spikes in voltage and effectively shorts them to earth without affecting the steady 12 volts in the lead. This protects any voltage sensitive devices connected elswhere on the loom, like the ESCII unit, the Rev Counter, a radio perhaps, etc etc.  My intention is to verify that I do not have a ballast system and then replace the unit with an automative capacitator (frequently called a "Condensor") of 2.2 micro farads. This will be connected to the chassis by its case and be wired to the input terminal(+) of the coil. Sorry to bore you with this, I was sort of thinking it through as I typed.

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P.S.  I just measured the resistance across the unit, between the two black leads and its Zero,  and between either black lead and the mounting bracket its infinite. So it is not a ballast resistor. The 73 ohms must be in series with the condensor, so I might add a resistor in the repacement.

 

P.P.S.   There is one on sale on eBay.

https://www.ebay.co.uk/itm/Sierra-RS-Cosworth-ignition-coil-resistor/224393688484?epid=28003500454&hash=item343ee7f5a4:g:bscAAOSwAQJgPUJc

OR. I think that this new BOSCH part should do but will need a small mod to the connector to wire it in.

https://www.onlinecarparts.co.uk/bosch-7428717.html

Edited by Sparepart
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