Jason Posted June 13, 2010 Share Posted June 13, 2010 Does anyone have some sensible instructions for what to do with the wiring when you replace the dynamo/alternator and control box on a Mk1 saloon? I'm having a little trouble making sense of what I have and things ain't right but I can't quite figure out how they should be! :-/Full explanation on my blog posting today Link to comment Share on other sites More sharing options...
James Posted June 13, 2010 Share Posted June 13, 2010 Check how the later alternator cars are wired up :) Link to comment Share on other sites More sharing options...
thescrapman Posted June 13, 2010 Share Posted June 13, 2010 Doesn't help much, especially if the original wiring has been re-used.When I fitted the replacement to the (slightly!) underpowered 15AC in mine I disconnected all the wiring to the 15Ac and the control box, and added 2 new wires.2 thick browns direct from the Big spades on the 18ACR to the plastic 4-way on the wing. You may need to unplug the one that came from the 15AC before.A signal cable from the small spade on teh 18ACR to the end spade on the plug that used to go into the black control box, that then went off to provide the dash light.How much of the original loom has been hacked out on yours??You just need to make sure you have the same 3 wires doing teh same thing as mine.I can convert back if I ever wanted for originality as well!CheersColin Link to comment Share on other sites More sharing options...
Jason Posted June 13, 2010 Author Share Posted June 13, 2010 jcarruthers wrote:Check how the later alternator cars are wired up :)James - I've got three wiring diagrams here, positive earth early, negative earth late and PI with alternator and control box - none of them list the brown/green wire as going to the dash, they all say the brown/yellow wire is the dash light/signal wire.Colin - I can't see that anything obviously chopped out but there are wires not connected to anything, it's all tidy but when you start tracing things you realise they don't go anywhere for instance the wire to the batter was three wires, all taped up in a tidy bundle but when you un-pick them you realise two of the wires don't go anywhere, they are just joined to each other in a tidy little loom piece. I've stripped it all back and remade the connections with one brown wire.So, will an alternator work OK if it's got just two wires connected? That's one to the dash light and one to the battery? Link to comment Share on other sites More sharing options...
James Posted June 13, 2010 Share Posted June 13, 2010 Yes - all it needs is the wire from the dash light and then one in to the battery and/or where all the high current feeds are on the solenoid. Link to comment Share on other sites More sharing options...
Jason Posted June 13, 2010 Author Share Posted June 13, 2010 I think Richard B might have a point that on the OE wiring all the current from the alternator/dynamo went through the Ammeter, with a modern higher output alternator that's too much current so some has been sent straight to the battery. Oh and how's the Atomic Barge with new reactor core? Link to comment Share on other sites More sharing options...
Glenn Posted June 13, 2010 Share Posted June 13, 2010 Jason - your coil voltages worry me. Non-ballast coil should be getting 12 volts +, also this shouldn't drop when revved.Could you try disconnecting the coil +ve ("sw") feed and running a temporary feed direct from the battery just to see if this cures the misfire?I think you are on the right lines pointing the finger at the Ammeter. Dunno how accurate this would be now - it would only measure the current drawn by the ignition switched circuits, and not the charging current which is going straight to the battery. So it's missing the point a bit now, but at least it should be safe.I guess the ideal would be to bypass the ammeter at this stage and fit a voltmeter at some future time.Good luck! Link to comment Share on other sites More sharing options...
thescrapman Posted June 14, 2010 Share Posted June 14, 2010 I don't have any issues with my ammeter using an 18ACR, it sometimes sits right at the C end for a minute or so after starting then settles down.I did have issues when I fitted a 55A A127, it hit the C hard, I just turned the lights on for a couple of minutes to balance the load, I had forgotten about the ammeter. I have a 60-0-60 one to use when I swap the 3-way dash thuingy for a rev-counter and move the others down to the cubby box.It was useful that it was still connected as said A127 failed after a couple of thousand miles and just kept charging at about 15A, slowly cooking the battery.spotted very quickly and switched all the lights on and swapped when I got home.I had a look at the wiring diagram last night.I think you can get away with using the brown/yellow that is presented at the original plugs to get your lamp connected via a short link wire to the new alternator.CheersColin Link to comment Share on other sites More sharing options...
Jason Posted June 14, 2010 Author Share Posted June 14, 2010 Cheers Glenn, as you can probably guess from my ramblings, my knowledge of vehicle electrics isn't great! I think the alternator is actually OK - it charges when it should and I've never had any issues with the battery discharging. None of the readings so far suggest real alternator issues. However, although I haven't tested everything, the wiring does cause me concern, makes me wonder if all is as it should be. Could there be a fault in the loom or in the low tension supply to the coil perhaps?I'm going to try the "hot wire" idea (a direct feed to coil from battery)and see if that makes a difference. Link to comment Share on other sites More sharing options...
Jason Posted June 14, 2010 Author Share Posted June 14, 2010 Colin, I think I'm going to have to stop by your place and have a rummage under your bonnet mate! Link to comment Share on other sites More sharing options...
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