Ignition Wiring Problem Reverting to Points System

Charlville

Charlville

Senior Member
Hi Fellow Barners
I wonder if I can ask for an opinion on the issue with the ignition wiring on my 1929 Sport Coupe (12vol negative earth, with a Nu-Rex alternator)

I’m in the process of removing the Pertronix set up and replacing it with the Nu-Rex modern points setup.

I’ve taken the following steps:

Added a used base plate to which I’ve soldered the longer pigtail

Connected the pigtail to the points terminal without pinching as instructed

Additionally modified the dimple area where the pop out would normally contact and added a wire which I’ve carefully insulated and connected this to the live side of the coil along with the wire from the ignition switch to the positive side of the coil.

The negative side of the coil is connected to the driver side connection on the terminal box.

My problem is that every time I turn the ignition on I’m blowing the safety fuse.

So I have a short somewhere and I’m not the world’s best electrician therefore it’s probably self-inflicted

Any assistance or advice would be appreciated as I’m stuck in the garage with her at the moment

Regards

Kevin
 
The negative side of the coil has to go directly to the distributor

The ignition switch should throw the 12v to the pos side of the coil
 
Hi Mitch

Thanks for the response
I was told to wire the other way so I'll try and swap over.
Do you think that could also blow the fuse?

Regards

Kevin
 
Charlville said:
Hi Mitch

Thanks for the response
I was told to wire the other way so I'll try and swap over.
Do you think that could also blow the fuse?

Regards

Kevin
Click to expand...

Yes

the points when closed ground it back to the neg side of the coil..

It sounds like you have that circuit hooked into the 12v feed instead
 
Hi Mitch

Pardon my ignorance a little further, do I need the terminal box connection to be moved over to the positive side or is it not required?

The original instructions I was working to are:

The points terminal on your distributor plate connects eventually to the positive coil post after going through the ignition switch.

The negative side of the coil goes to the driver’s side junction box terminal .

Having a 12v system you MUST make sure your coil measures 3.0 OHM’s. This measurement is made using a good quality OHM meter between the two threaded coil posts.

Can I assume this was for a positive earth setup?

Thanks again for your help, it's been a long day!

Regards

Kevin
 
Charlville said:
Hi Mitch

Pardon my ignorance a little further, do I need the terminal box connection to be moved over to the positive side or is it not required?

The original instructions I was working to are:

The points terminal on your distributor plate connects eventually to the positive coil post after going through the ignition switch.

The negative side of the coil goes to the driver’s side junction box terminal .

Having a 12v system you MUST make sure your coil measures 3.0 OHM’s. This measurement is made using a good quality OHM meter between the two threaded coil posts.

Can I assume this was for a positive earth setup?

Thanks again for your help, it's been a long day!

Regards

Kevin
Click to expand...

not on a negative ground system

Yes to a pos set up on the inst
 
Chase the short with an ohm meter and stop blowing fuses. Get a wiring diagram out and follow it. It is very simple.
 
I have a simple 12v light in a socket with the 2 leads ending in alligator clips. If you have something similar, just remove the blown fuse and connect the 2 clips across the terminals where the fuse goes, then go around checking for the short. The light will go off when you find the short that is blowing the fuse.

This is a simple way of checking for a short circuit.

Also, I think Mitch has nailed down your problem.
 
wiring-diagramcolor2sm.jpg
 
Here's a simplified ign circuit for pos grd. For a neg grd, reverse all four polarities. Sometimes simple visual helps.
 

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Hi All

All now back in track as I've wired as follows (as per Mitch discussion above)

Points to coil -

Ign SW to coil +

Big fat spark, no fuse issues

Just get her timed up properly and hopefully away we go :)

Thank to all who responded
 
Post #5 If you have a 1.4 OHM coil no problem with 12V if you use an external resistor. If using 3.0 OHM coil no external resistor is required.

Source: FSI
 
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