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how to test ignition coil

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Lobo:
Hi El_burro,

... "jumping on threads" is both welcomed, and more often than not, beneficial to all as new questions arise. And frankly, I'd quite like someone to jump in too... as HT circuits are not my strong point.

However.. my thoughts until put right...

At 14 ohms this secondary (HT) winding is certainly duff.... it sounds like some kind of internal short. Are you quite sure you've got the correct scale on your multimeter.... if you'd said 14K ohms we might have been in the right ball park; for whilst I can't find a specific value for these old Hondas, most searches I do, state HT coil norm ranges between 10 Kohm - 20 Kohms.... ie about 1000x the value you're getting.

So yup, your HT coil is indeed showing continuity (ie not open circuit)..... but in this case, too much!

Simon.

(the primary winding / low voltage circuit should be abouts 5 ohms I think)

AshimotoK0:
I am just getting all of the materials together to do a write-up on refurbing coils (materials must be cheap and readily available to everyone) . Main thing is replacing the HT leads (as I briefly mentioned in an earlier post). So watch this space ! On the primary, if you don't have a meter that measures low ohms accurately then connect the two primaries in series on the pair of coils and connect (briefly) across a 12v battery. Measure the voltage between the centre point of the coil connections and + terminal and then negative terminal. If the coils are OK then the coils will act as a 'potential divider' and you should have roughly half of the battery terminal voltage at the mid point (within 10%). Obviously, if you have a meter that measures low resistance accurately , which from memory is typically about 4.5 Ohms, you can simply measure it. (this assumes that both coils don't have a faulty primary (RARE!))

I think shorted primaries are a rare occurrence on 'Tec' /  Nippon Denso coils though (well on all of the ones I have seen) , it always seems to be the  the HT lead  that fractures , hence my restoration write-up I am doing. On the US import CB350K1 I got from DK last year, all the electrics were all in  pretty much pristine condition for a 45 year old bike but the HT leads look floppy around the exit point from the coil and, even though the resistance meters out  OK, I will replace them.

Ash

SteveD CB500K0:
Ash - a few years back I added a FAQ on the US site which showed how one member had replaced the HT leads on original coils (lots of epoxy if I remember)

Have you seen this?

Maybe we need a FAQ on here as I see more and more really useful stuff that won't get indexed properly (eg Bodd's 400/4 wiring diagram won't show up in a search as it doesn't use the words "400", "wiring" and "diagram" anywhere in the text!

AshimotoK0:

--- Quote from: SteveD CB500F on January 17, 2015, 09:53:19 AM ---Ash - a few years back I added a FAQ on the US site which showed how one member had replaced the HT leads on original coils (lots of epoxy if I remember)

Have you seen this?

Maybe we need a FAQ on here as I see more and more really useful stuff that won't get indexed properly (eg Bodd's 400/4 wiring diagram won't show up in a search as it doesn't use the words "400", "wiring" and "diagram" anywhere in the text!

--- End quote ---

Yes I am using epoxy (liquid) and black epoxy putty Steve. Problem is I have access to stuff other members (test gear/chemicals)  may not have so I want to stick to readily available materials. One hard to get item is the thin walled rubber sleeving that goes over the HT lead. I'ts around 1mm wall thickness which is really  hard to find in nitrile rubber.

Ash.

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