Chris59 Posted October 11, 2011 Report Share Posted October 11, 2011 Hello guys, Sorry to ask, I have lost the info in my computer : how to modify an old control box to allow the fitment of an alternator on a TR3A, without alteration to the main harness ? This modification consist in a few "bridge" connections and some others modifications in the old (and then unused) dynamo' control box, as the alternator don't need it anymore. Who can help ? Chris. Quote Link to post Share on other sites
Ashley James Posted October 11, 2011 Report Share Posted October 11, 2011 I don't think it's necessary to do anything other than connect the output from the alternator straight to the positive of the battery. Alternators produce a lot more current than dynamos, so best not test old wiring with it. Obviously the car will be positive earth and the Ammeter will show a permanent dish charge if it's reversed, but it'll all work fine. Ash Quote Link to post Share on other sites
Chris59 Posted October 11, 2011 Author Report Share Posted October 11, 2011 (edited) Ash, I will keep the old control box + wiring to allow the "retrofit" of a dynamo later, if needed, but it will be a "fake" control box, with all the innards removed. This particular car has a brand new wiring loom, and I don't want to cut any wire, thus the need to connect the wire via the old control box. I have bring theses mods to some cars, but have lost the scheme of mods to bring to the control box BTW, a car with alternator must be negative earth. Chris. Edited October 11, 2011 by Chris59 Quote Link to post Share on other sites
Ashley James Posted October 11, 2011 Report Share Posted October 11, 2011 Sorry I meant negative earth, but as I said you can simply fit an alternator, connect the output to the battery and reverse anything that reads backwards because you've changed polarity. No need to to do anything to the regulator at all because alternators regulate themselves. Ash Quote Link to post Share on other sites
ianc Posted October 11, 2011 Report Share Posted October 11, 2011 Technicalities CD, Section J4. TR Action 248, March 2011. Ian Cornish Quote Link to post Share on other sites
Chris59 Posted October 11, 2011 Author Report Share Posted October 11, 2011 Many thanks Ian, I have found it on p.45, well done ! Chris. Quote Link to post Share on other sites
Fireman049 Posted October 12, 2011 Report Share Posted October 12, 2011 Hi Chris59, I've carried out the conversion to an alternator on my TR3A and still use the (modified) control box as I want the car to look 'original'. If you could let me have your email address I can send you some photo's showing the modified wiring. I've been unable to attach the photo's to this reply as they are too large. Tom. Quote Link to post Share on other sites
jean Posted October 14, 2011 Report Share Posted October 14, 2011 Chris, I would in any case add an extra wire to cope with the higher load produced by the alternator in case of low battery. I WOULD NOT RISK TO FRY THE LOOM Quote Link to post Share on other sites
ianc Posted October 14, 2011 Report Share Posted October 14, 2011 If the alternator is of modest output, such as the 34 amp rated unit which I have fitted (as on early TR7s), then the existing wiring, provided it is in good condition, should be adequate. However, if a device capable of driving a cooker, refrigerator and washing machine has been fitted, then suitable precautions need to be taken (see TR Action 248)! Ian Cornish Quote Link to post Share on other sites
Ashley James Posted October 15, 2011 Report Share Posted October 15, 2011 Surely the sensible thing to do is connect the alternator straight to the battery with a good heavy wire. That's what all the conversions we've seen do and it means that apart from reversing connections on anything that reads backwards, the job is done and no mods are necessary. Ash Quote Link to post Share on other sites
BlueTR3A-5EKT Posted October 15, 2011 Report Share Posted October 15, 2011 Connecting the alternator main charging wire direct to the battery is an excellent idea but you will get odd information and needle swings from your ammeter. The ammeter will tend to shew a continuous charge as the amps flow from the charging input of the alternator at the battery into the car circuit where the demand is. On TR2-3-3A-3B - I have not looked at the standard circuit for TR4-4A Cheers Peter W Quote Link to post Share on other sites
Chris59 Posted October 15, 2011 Author Report Share Posted October 15, 2011 Hello guys, Thanks for all the inputs. On this perticular car, I'll more than double the "charging" cable : the alternator is a 45amp, and the orignal cable isn't big enough to cope with the power. About the ammeter, I don't think it is really usefull on a car with an alternator : a volmeter is more adequate, IMHO. Cheers, Chris. Quote Link to post Share on other sites
Ashley James Posted October 15, 2011 Report Share Posted October 15, 2011 If you connect the alternator directly to the battery, the ammeter will never show a charge, it'll just show the current being drawn by ignition, lights etc. If you wire a 45 Amp alternator through the ammeter, it'll go up in smoke! And if you leave the wiring standard, the dynamo can go back on if originality becomes important. Ash Quote Link to post Share on other sites
qkingston Posted January 6, 2021 Report Share Posted January 6, 2021 Ok so I've fitted the thin belt alternator conversion to my 4a restoration project (+ new loom) and am looking for a bit more detail on the modification to the old control box. I assume you can remove the internals and replace with a suitable heavy duty connection to link the correct wires? I've seen a couple of posts with the 'Dynator' fitment but not sure if the alternator arrangement is a bit different; this is not about the wiring set up but more about the modification to the old control box internals Many thanks David Quote Link to post Share on other sites
Lebro Posted January 6, 2021 Report Share Posted January 6, 2021 (edited) Remove internals. Using reasonably heavy wire the only connections should be: D to A & A1 F to E Disconnect earth wire from E, & discard Connect ign warning light wire (thin yellow) to E Connect field wire from alternator to F Connect power wire from alternator to D Leave wires on A & A1 as before. Bob. Edited January 6, 2021 by Lebro Quote Link to post Share on other sites
qkingston Posted January 6, 2021 Report Share Posted January 6, 2021 Thanks Bob, what do you mean by reasonably heavy wire? 30A, 40A? (Lucas LRA 100 Alternator), and was that using a connector block of some sort? Quote Link to post Share on other sites
Fireman049 Posted January 6, 2021 Report Share Posted January 6, 2021 (edited) Edited January 8, 2021 by Fireman049 Quote Link to post Share on other sites
Fireman049 Posted January 6, 2021 Report Share Posted January 6, 2021 (edited) Wiring diagram removed. Tom. Edited January 7, 2021 by Fireman049 Quote Link to post Share on other sites
Lebro Posted January 6, 2021 Report Share Posted January 6, 2021 (edited) . Edited January 16, 2021 by Lebro Quote Link to post Share on other sites
Hamish Posted January 6, 2021 Report Share Posted January 6, 2021 This is my annotated regulator for the alt conversion for an on car reminder. Tom’s wiring pic is the right one that I added my annotation when he helped me. Quote Link to post Share on other sites
Lebro Posted January 6, 2021 Report Share Posted January 6, 2021 (edited) . Edited January 16, 2021 by Lebro Quote Link to post Share on other sites
qkingston Posted January 6, 2021 Report Share Posted January 6, 2021 Thanks Guys, all really helpful Best Regards David Quote Link to post Share on other sites
TorontoTim Posted January 6, 2021 Report Share Posted January 6, 2021 And if you'd prefer a ready-made solution... https://www.holden.co.uk/c/electrical/dynamos_starters/dummy_control_boxes_dynalites_1 Quote Link to post Share on other sites
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