ahebron Posted July 20 Report Share Posted July 20 As Colin said could it be the old cable earthing the instrument. Have you tried refitting the old cable and seeing what happens? Link to comment Share on other sites More sharing options...
SpitFire6 Posted July 20 Report Share Posted July 20 Hi, The lamp is powered by the "D" connector on the alternator. As one side of the lamp is connected to the White ignition wire, it can only be illuminated if the "D" terminal pulls current. The "D" terminal is the internal connection of the voltage regulator & triple diodes that normally feed the voltage regulator. If the internal regulator does not initially get any current from the ignition bulb, it might need to be revved to 1500+ before it excites and starts charging. It is the only circuit/wire on the whole car that does not cause a problem due to poor earth! Cheers, Iain. Link to comment Share on other sites More sharing options...
johny Posted July 20 Report Share Posted July 20 22 minutes ago, SpitFire6 said: Hi, The lamp is powered by the "D" connector on the alternator. As one side of the lamp is connected to the White ignition wire, it can only be illuminated if the "D" terminal pulls current. The "D" terminal is the internal connection of the voltage regulator & triple diodes that normally feed the voltage regulator. If the internal regulator does not initially get any current from the ignition bulb, it might need to be revved to 1500+ before it excites and starts charging. It is the only circuit/wire on the whole car that does not cause a problem due to poor earth! Cheers, Iain. Dont forget this is a non standard Denso 4 connection alternator fitted so not sure theres a terminal marked D as such.... Link to comment Share on other sites More sharing options...
Paul H Posted July 21 Author Report Share Posted July 21 On 19/07/2024 at 13:21, Colin Lindsay said: Wonder if it was actually earthing via the old speedo cable? The Speedo case has plastic holders for ignition , oil and main beam so no earth Paul Link to comment Share on other sites More sharing options...
Paul H Posted July 21 Author Report Share Posted July 21 I think I have solved the issue , I removed the alternator connection to the coil +VE and connected to Brown/Green which originally went to the old dynamo . The Brown Green is linked to Brown Yellow which goes to the ignition bulb . With ignition on it light but stayed on with the engine running at 2000 revs plus. The Volt meter showed no charge and hovered around 12V. Checked the output from the alternator and zero so I must have fried the internal regulator with multi testing😱. Now looking for a replacement regulator for the Denso. Coming back to the original wiring I have to accept it was incorrect wiring when I installed the Denso and linking to the coil was incorrect and that the Ignition light has never worked . My sincere apologies to all who have persevered with solving my issue in particular @johny and @Pete Lewis. Hopefully the replacement regulator with sort the issue and should the alternator misbehave itself in the future I’ve got a “worry” light which works . Apologies again to all who helped . Paul Link to comment Share on other sites More sharing options...
Colin Lindsay Posted July 21 Report Share Posted July 21 What's the centre made of; could it still by-pass the plastic outer or screw connectors and earth via what metal there is? I remember cars in days gone by earthing through the choke cable, which could on occasion glow red... but it was all metal in that case. Link to comment Share on other sites More sharing options...
Paul H Posted July 21 Author Report Share Posted July 21 35 minutes ago, Colin Lindsay said: What's the centre made of; could it still by-pass the plastic outer or screw connectors and earth via what metal there is? I remember cars in days gone by earthing through the choke cable, which could on occasion glow red... but it was all metal in that case. Hi Colin, the bulb housing looks like it’s made of Bakelite Paul Link to comment Share on other sites More sharing options...
johny Posted July 21 Report Share Posted July 21 54 minutes ago, Paul H said: I think I have solved the issue , I removed the alternator connection to the coil +VE and connected to Brown/Green which originally went to the old dynamo . The Brown Green is linked to Brown Yellow which goes to the ignition bulb . With ignition on it light but stayed on with the engine running at 2000 revs plus. The Volt meter showed no charge and hovered around 12V. Checked the output from the alternator and zero so I must have fried the internal regulator with multi testing😱. Now looking for a replacement regulator for the Denso. Coming back to the original wiring I have to accept it was incorrect wiring when I installed the Denso and linking to the coil was incorrect and that the Ignition light has never worked . My sincere apologies to all who have persevered with solving my issue in particular @johny and @Pete Lewis. Hopefully the replacement regulator with sort the issue and should the alternator misbehave itself in the future I’ve got a “worry” light which works . Apologies again to all who helped . Paul From what I can see Paul your brown wire is terminal S which is sensing so goes straight to battery to tell the alternator the exact voltage output required. The white is IG which comes from the ignition switch and Brown/yellow is L that controls the ignition light. The white wire going to the coil is correct as the coil +ve terminal is fed directly from the igntion switch via a white wire and if this is not powered the alternator probably wont work! Link to comment Share on other sites More sharing options...
johny Posted July 21 Report Share Posted July 21 In fact looking at the original wiring diagram your colours are good. Brown/yellow goes to old volt reg terminal D where internally its connected to terminal W/L that has the brown/yellow from the ignition light. Brown on reg terminal B comes direct from battery so should then go to terminal S on the alternator and white comes from the coil as thats the nearest ignition switch supply👍 Link to comment Share on other sites More sharing options...
Paul H Posted July 21 Author Report Share Posted July 21 Hi Johnny . I switched back the white to +VE on the coil . The alternator now charges with no ignition light . I’m left with a thin Brown / Yellow from the ignition light with no home . Where should this go now . Paul Link to comment Share on other sites More sharing options...
johny Posted July 21 Report Share Posted July 21 well if I was installing it (and I maybe soon) I would put the brown/yellow from the ignition light onto the regulator terminal W/L (as it was originally) and the large brown/yellow from the alternator onto terminal D of the regulator (also as originally). Otherwise of course the two can just be connected together to avoid the regulator all together and as theres very little current flow the connection doesnt have to be great but of course well insulated... Link to comment Share on other sites More sharing options...
Graham C Posted July 21 Report Share Posted July 21 Link to comment Share on other sites More sharing options...
johny Posted July 21 Report Share Posted July 21 Have you found where the plain brown wire from the alternator goes Paul? Link to comment Share on other sites More sharing options...
Graham C Posted July 21 Report Share Posted July 21 Hello Pete, this waiting diagram for a GT6, shows a brown/yellow from alternator and white back to fuse. If you switch on the ignition do you get any current/ voltage on the B/y cable? If so then I would think this is the power to the bulb. Graham Link to comment Share on other sites More sharing options...
Paul H Posted July 21 Author Report Share Posted July 21 11 minutes ago, johny said: Have you found where the plain brown wire from the alternator goes Paul? Plain brown goes direct to positive terminal on battery Paul Link to comment Share on other sites More sharing options...
johny Posted July 21 Report Share Posted July 21 Great just as it should. Youre almost there👍 Link to comment Share on other sites More sharing options...
Paul H Posted July 21 Author Report Share Posted July 21 49 minutes ago, johny said: well if I was installing it (and I maybe soon) I would put the brown/yellow from the ignition light onto the regulator terminal W/L (as it was originally) and the large brown/yellow from the alternator onto terminal D of the regulator (also as originally). Otherwise of course the two can just be connected together to avoid the regulator all together and as theres very little current flow the connection doesnt have to be great but of course well insulated... Currently the thick brown / yellow from the alternator is connected to the 3 thick brown cables from the old regulator box using a copper shunt which has 3 male spades . If I detach the brown yellow from the shunt and connect to the brown yellow from the ignition light and turn on ignition the light doesn’t not come on Paul Link to comment Share on other sites More sharing options...
johny Posted July 21 Report Share Posted July 21 thats a surprise! Is there a small diagram of the 3 pin terminal labelling like this on the right hand side of the nameplate? Link to comment Share on other sites More sharing options...
Paul H Posted July 21 Author Report Share Posted July 21 2 minutes ago, johny said: thats a surprise! Is there a small diagram of the 3 pin terminal labelling like this on the right hand side of the nameplate? Snap Paul Link to comment Share on other sites More sharing options...
johny Posted July 21 Report Share Posted July 21 so with the white wire terminal getting 12v from the coil the ignition light wouldnt work when connected to the brown/yellow of the alternator? I believe the white wire needs power to turn the alternator on... Just read that the P type doesnt need anything connecting to that terminal as its pulsed for powering a tacho so try disconnecting the brown wire Paul. Link to comment Share on other sites More sharing options...
johny Posted July 21 Report Share Posted July 21 Heres the link I was reading.... Denso alternator wiring query | Rods 'n' Sods - UK Hot Rod & Street Rod Forums (rodsnsods.co.uk) Link to comment Share on other sites More sharing options...
Paul H Posted July 21 Author Report Share Posted July 21 1 hour ago, johny said: so with the white wire terminal getting 12v from the coil the ignition light wouldnt work when connected to the brown/yellow of the alternator? I believe the white wire needs power to turn the alternator on... Just read that the P type doesnt need anything connecting to that terminal as its pulsed for powering a tacho so try disconnecting the brown wire Paul. Disconnected brown and no Change ie no ignition light Paul Link to comment Share on other sites More sharing options...
johny Posted July 21 Report Share Posted July 21 so brown disconnected, white on coil +ve and ignition light on brown/yellow? Oh and earth good all the way from alternator to battery? Link to comment Share on other sites More sharing options...
Paul H Posted July 21 Author Report Share Posted July 21 6 minutes ago, johny said: so brown disconnected, white on coil +ve and ignition light on brown/yellow? Oh and earth good all the way from alternator to battery? Yes though I’ll add a temp fixed earth to the alternator to be sure and test again Paul Link to comment Share on other sites More sharing options...
Paul H Posted July 21 Author Report Share Posted July 21 4 minutes ago, Paul H said: Yes though I’ll add a temp fixed earth to the alternator to be sure and test again Paul Earth tested ok and no change Paul Link to comment Share on other sites More sharing options...
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