Voltage Regulator Reconfigured for Alternator

[Andy8421]

This looks like excellent quality work.

It is difficult to fully see the connections, but assuming everything is 'straight through' then your suggested wiring sequence "Tabs on extreme left & right are for alternator feed and solenoid. Centre tab is for Blue & Blue/Yellow feeding vehicle electrical system" doesn't match your final circuit diagram a few posts up.

If you are trying to achieve your final circuit diagram (which I think was the best), then the solenoid connection should go to the centre tab, and the alternator cable / feed to the electrical system should go to extreme right or left depending on which way round you have mounted the fuses.

FWIW, I think this is a very good solution to fitting an alternator, keeps the appearance and character of the wiring intact and introduces valuable safety features. If you are keen, you could approach Autosparks (or maybe Clive Chapman) with a suggestion they manufacture a similar product. If that isn't economical, perhaps a kit of the bits you used (fuses, tabs, insulating washers) could be made available for DIY use. The only downside is replacing the fuses is a bit of a faff, but if they do blow then arguably you have had a significant wiring failure and likely have saved yourself a much bigger job.

I haven't quite figure out how bespoke I want to go with the wiring on my Sprint restoration, but I will give your approach serious consideration.

Andy.

[Bodmin]

It is difficult to fully see the connections, but assuming everything is 'straight through' then your suggested wiring sequence "Tabs on extreme left & right are for alternator feed and solenoid. Centre tab is for Blue & Blue/Yellow feeding vehicle electrical system" doesn't match your final circuit diagram a few posts up.

You’re absolutely correct! I can’t believe I failed at the final hurdle. Glad somebody is awake. Thank you also for the kind words.

As per the diagram the centre tab is for the solenoid, left & right tabs are for alternator and feed to electrical system.

I’ve installed a red 50 amp fuse on the alternator side, and blue 40 amp on the feed side. No science involved, these are the only ones I had handy. Not sure if I should increase or decrease either of these values. Might just get everything back together and see if it all works first.

I’m not sure whether to keep the backplate earthed. It’s a handy tab for the earth spade, but if the backplate isn’t earthed I don’t think any harm would come if anything did touch the backplate. It would just become live with no consequences. Might even drill out and isolate the earth tab so I can keep it in place.

[Andy8421]

Not a bad idea to isolate the backplate, although if you have all your insulating washers in the right place is shouldn't matter.

I would be tempted to up the rating of the alternator fuse. Weird stuff happens with rotating electrical machinery. In the case of the alternator, a drop in load (you switch the headlights off for example) results in a pickup in voltage and the regulator dropping the current to the rotor to compensate. The rotor is an inductor and doesn't respond immediately, the regulator won't be instantaneous either, the alternator output voltage spikes which can lead to a current spike. Steady state is fine, it is just the transients at the point the load changes that cause the problems.

Current vehicle practice seems to fuse the alternator at 2x to 3x the rated output. That seems about right to me.