• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

test tach

Share this page

tahoe healey

tahoe healey

Yoda
Country flag
Offline
I just got a new tact-dwell meter that has an induction contact for the tach which goes onto a spark plug lead. It says to face the attachment with the lable towards the spark plug. Doesn't work. When reversed with the attachment lable away form the plug it works fine. On my 4-Runner it has to have the lable towards the plug. My BJ8 has been changed to neg-ground by the previous owner. Could the coil have not been reversed at that time? Am I doing any harm? She runs well.
confused.gif
 
The coil "should" have been reversed when the battery ground was reversed.

To make everything come out correctly with stock Healey ignition components, for negative ground, the coil terminal marked SW or - should go to the points & battery shutoff ground wires. The terminal marked CB or + should go to the ignition switch.

It won't do any harm to have it either way but there may be slightly higher spark voltage available with the correct connection.
D
 
Dave, thank you very much! I switched it out this morning and I've got more power and a smoother idle. The diagnostic tach works properly too. I've been driving a long time the other way. One should never assume anything about these cars.
thumbsup.gif
 
If I was reading the posts correctly what had happened was that you made your coil a step down transformer instead of a step up which is the way it should go. Coils or transformers (same thing)do not care which way power enters or leaves but the out come is determined that way and of course by the amount of windings on the primary and secondary sides.
CDK
 
I read somewhere that spark plugs do care. The center post is better designed to take heat and there would be more wear to the electrode or something like that. Anyway I'm feeling the difference in proformance and thats good! The PO seemed to do many things half way but that keeps me busy.
 
TH,
My post was somwhat misleading.I gave you a good discription of a AC transformer and its operation.On our cars which are DC we need to induce a field change in the primary coil in order for the secondary side (output)To release its charge.This field change is obtained by removing/grounding with the points the current to the pri side of the coil.In theroy the wires on the coil could be hooked up on either side.This sounds right but the more I think about it the more I confuse myself on a really simple circut.Dave R.if you can explaine this better I would appreciate it.I found a lot of wriiten theroy but could not find any diagrams(picture is worth a thousand words)
Scratching my head
CDK
 
Dave,
Thanks.My error came in thinking that the output of the secondary would always be plus to minus.I work a lot more with AC coils and transformers (yes both, even though I said they were the same)and did not allow for the polarity concepts.That was a good artical and I liked the pencil test.I am going to do this just for the fun of it.
Hats off to the doyen of tech
CDK
 
Back
Top