Ian Vincent Posted December 15, 2015 Report Share Posted December 15, 2015 I need a bit of help with an electrical problem - it's not my strong point. (don't ask me what is!) I have a TR3a that has been converted to negative earth and an alternator. It also has an Advance Autowire Powerblock wiring system; one of the Powerblock features is a Power Terminal which is switched via an ignition relay. I have attached a copy of the circuit diagram for the Powerblock It is currently fitted with a QH copy of a 28 Amp Lucas 15ACR but I suspect that it is no longer working properly as the ammeter never shows it moving into the positive zone. When I originally fitted it, it did. My current wiring is as shown on the first of the attached diagrams, it was provided by Phill Tucker in response to a query on the forum back in 2011. I have acquired now a new Nippon Denso / Kubota 40 amp item to replace it. It has one main connector and three other smaller ones (see picture). My problem is how to wire the replacement up. After a search on the internet, I have found two similar diagrams, (Nippon Denso #1 and #2 attached). Both of these show a permanent live connector between the alternator and the battery. It is terminal 1 on diagram ND #1 or terminal S on diagram ND #2. On the latter diagram it states that S is used by the regulator to monitor the charging voltage at the battery. Referring to ND#2, is there a reason why I can't just connect terminal S directly to the main output terminal ( via a suitable fuse and avoid having to run an extra wire back to the battery. To my non expert eye that looks to be exactly what my original wiring does with the Lucas/QH alternator. In fact looking at the diagrams again and bearing in mind that my Power Terminal is switched anyway, is there any reason why I can't connect terminal IG directly to terminal B. Any help would be appreciated. Rgds Ian Alt wiring.pdf Powerblock Circuit Diagram.pdf Quote Link to post Share on other sites
RobH Posted December 15, 2015 Report Share Posted December 15, 2015 (edited) You could connect the sense wire directly at the back of the alternator Ian. Its only connected at the battery to compensate for the voltage drop on the main cable. As long as the main wire is of reasonable thickness, on the short run in a TR it probably won't make any discernable difference. No need for a fuse either - in fact that is probably a bad thing to do as if the fuse doesn't make a good connection for any reason there will be no voltage regulation from the alternator and the output will rise to its maximum. Its not a good idea though to do the same with the IG wire as that is intended to be switched rather than permanently live. It looks like the power relay in your 'block' does that so if IG is connected to the point shown used for the ignition lamp at the G3 fuse, that would do. Edited December 15, 2015 by RobH Quote Link to post Share on other sites
Ian Vincent Posted December 16, 2015 Author Report Share Posted December 16, 2015 Many thks for the response Rob, (and for taking the time to plough your way through my description). I can easily provide a switched feed by routing a wire from the coil across to the alternator. It amounts to the same thing. Rgds Ian Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.