Been a bit of a plonker a bought a new coil for the MK1 when it turns out I probably didn't need to. Plot is the existing one (on a MK1 1.8 GTI) is likely the 1983 original, going by the Bosch manufacturing date on it, so 40 years old. Anyhow, Bentley gives US car specs. but Haynes also quotes for UK cars, not that there's very much difference between the two, but I'm using the latter. They both give the various test readings for cars with either ignition systems that have distributor contact breakers and those without ('transistorized', as is the case with my car)... I mistakenly used the wrong 'breaker' set, thought the coil was outside of specs. when in reality it was bang on, hence ordering the new coil. Couldn't get another Bosch, but did find an equivalent NGK (it's 100% the correct one for the car, have checked and double checked). So to the point, these is the correct ranges for 'breakerless' UK cars - Primary 0.55 to 0.75 Ohms Secondary 2500 to 3500 Ohms The new NGK is 0.8 and 7400 Ohms, so a bit off for the primary winding, but way off for the secondary. If I've understood correctly the greater the Ohms the less 'power' getting through so being more or less double the Ohms it should be would presumably have an impact on it's proper working? Over and above what I've read in Bentley / Haynes, I know nothing else about coils, maybe things have improved over the years and the NGK is infact better for having the greater secondary Ohm reading?
I would make three observations: 1 Have you fitted it and is it working and is the car running well? If so, happy days, don’t overthink it. 2 If you haven’t fitted it, try it and see if it works and the car runs well. If it does, happy days, don’t overthink it. 3 You are massively overthinking it
Car's engineless at the moment and likely to be so for a while... if the NGK is faulty I'd prefer to get it back now rather than try months down the line when I'd likely be told where to go. Don't agree about overthinking it either, my understanding is an incorrect / faulty coil can cause both damage to the ignition system and / or poor running. The specs. are presumably for a reason, why else specify them?
The age of the coil is irrelevant-if it’s working that’s it, no moving parts in there. The coil on my ‘86 E28 is original and work’s faultlessly and I have no desire to change it because that’s all part of the originality and to be honest I genuinely believe that the older kit was built with longevity in mind.
A faulty coil would be open circuit on either winding imho. 7400 ohms secondary is not out of the ordinary for ignition coils, I did a Suzuki a while back with similar readings and an excellent spark output. Send an email to NGK for clarification. You can test the coil with a 12v battery, just don't burn it out..
VW coils vary, a lot. I had a quiet day, and decided to do some checks on my stock, Quite a variance. Didn't bin any.. Lol Jon
