Ignition Coil Resistance Wire

[Jonathan Pounsett]

Why is the wire between the coil and the fuse box a translucent resistance wire? What does it do that makes it different to any other wire?

[cam.in.head]

the coil on a points type ignition system only runs at around 6-9v rather than 12v.the resistance wire keeps the coil voltage correct.once you operate the starter this voltage would fall lower but a bypass wire on the stater solenoid brings it up to full voltage ( which during cranking could be 10-11v) and this also give a temporary stronger spark to aid starting.

this system only applies to a conventional points type distributor.if you ever fit an electronic ignition distributor from a gte for example then you need to run a constant 12v non resistive wire from the ignition switch.

[Jonathan Pounsett]

4 hours ago, cam.in.head said:

the coil on a points type ignition system only runs at around 6-9v rather than 12v.the resistance wire keeps the coil voltage correct.once you operate the starter this voltage would fall lower but a bypass wire on the stater solenoid brings it up to full voltage ( which during cranking could be 10-11v) and this also give a temporary stronger spark to aid starting.

this system only applies to a conventional points type distributor.if you ever fit an electronic ignition distributor from a gte for example then you need to run a constant 12v non resistive wire from the ignition switch.

Thanks @cam.in.headfor a very informative and interesting reply. I knew someone in the club would know the answer.

[cam.in.head]

youre welcome.

[Nivlek2525]

On 09/04/2022 at 16:36, cam.in.head said:

the coil on a points type ignition system only runs at around 6-9v rather than 12v.the resistance wire keeps the coil voltage correct.once you operate the starter this voltage would fall lower but a bypass wire on the stater solenoid brings it up to full voltage ( which during cranking could be 10-11v) and this also give a temporary stronger spark to aid starting.

this system only applies to a conventional points type distributor.if you ever fit an electronic ignition distributor from a gte for example then you need to run a constant 12v non resistive wire from the ignition switch.

So pleased I found this. Been pulling my hair out trying to work out why I had a see-through wire. Thanks. Havent owned a car with points since I passed my test.

[rutts]

On 09/04/2022 at 16:36, cam.in.head said:

the coil on a points type ignition system only runs at around 6-9v rather than 12v.the resistance wire keeps the coil voltage correct.once you operate the starter this voltage would fall lower but a bypass wire on the stater solenoid brings it up to full voltage ( which during cranking could be 10-11v) and this also give a temporary stronger spark to aid starting.

this system only applies to a conventional points type distributor.if you ever fit an electronic ignition distributor from a gte for example then you need to run a constant 12v non resistive wire from the ignition switch.

Don't do what I did on mine. Changed to electronic ignition new 12v feed and ran ballast coil. It got hot dam hot. 

[Nivlek2525]

11 hours ago, rutts said:

Don't do what I did on mine. Changed to electronic ignition new 12v feed and ran ballast coil. It got hot dam hot. 

I'm converting the SR over to a GTE engine and loom. When I bought the engine I got the engine loom complete and the engine bay part of the loom cut of crudely from the bulkhead.  The gte and Sr looms are almost the same so I could splice in the fuel pump relay connector and the plugs for the coil etc but couldn't work out what the resistance wire was so it totally threw me.  Just need to run a new wire to the fuel pump.

Nearly done.

Edited February 6, 2023 by Nivlek2525