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Electrical problem 120-130 1967

Hi,

My 'amp' light came on while driving - sporadically at first, and then permanently. Fan belt tension and fuse # 1 are fine - no corrosion in the fuseholder. With the engine running there is 12V at the regulator B+ terminal and no reading at the D+ terminal. I swapped the dynamo (generator) with a newly reconditioned one - no improvement. I fitted a new regulator - no improvement. Both parts were supplied by an Amazon specialist so I'm assuming that they're right. Now I'm stumped. After I fitted the dynamo, I polarised it by flashing a wire between the DF terminal on the dynamo and the battery positive terminal (the dynamo was still connected to the regulator) - now I'm wondering if it makes any difference
a) if the dynamo is connected to the regulator when this is done?
b) if the engine should be running or not? (it wasn't)
b) if the lead should be connected to the battery first and then the dynamo or vice-versa? (or does it make any difference at all?...)
c) if a thin lead is sufficient? - it was thin cable (like speaker wire)

Anyone have any thoughts on the above? Can anyone tell me how I can check the dynamo and regulator for output with a voltmeter - the Haynes manual is vague as to what cable goes where for testing and I'm not an electrical expert (as you may now have gathered...) I would have assumed that the dynamo D+ terminal would give some sort of output but it doesn't.

Any help would be very much appreciated

Aidan








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    Electrical problem 120-130 1967

    I had the same problem awhile back. It turned out to be a very simple solution. The wire to the Alternator had work hardened an broke inside the insulation. Hope this helps.








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    Electrical problem 120-130 1967

    Aidan;

    If Fuse1 and associated connections are in order, a lit AMP light indicates no dynamo output, since this indicator is connected across dynamo output and battery (by way of the IGN sitch and a long path). This is a bit unusual and confuses some...under normal conditions , voltage is on BOTH sides of lamp, and therefore it does NOT light...remember, to light a lamp, voltage must be applied ACROSS it...so when dynamo fails and output goes to zero, IT provides the ground return path...voltage ACROSS lamp resuls, and lamp lights.

    You would expect the B+ terminal of regulator to show battery voltage anytime (even when engine is not running), since it's indirectly connected to the battery (see wiring diagram).

    No voltage reading on the D+ is again indicative of no dynamo output. This terminal is connected to the B+ terminal by the "cut-out relay" within the regulator. In this way the "cut-out relay" prevents the dynamo from discharging the battery when engine is OFF.

    I believe you may have damaged field control of the regulator by leaving it connected when you "polarized the field". My Haynes manual does state it should be disconnected for this. I suggest you try a new regulator to get your dynamo system working again, but you may want to consider one of my alternator upgrades (see: http://www.intelab.com/swem/altkit.htm).

    Cheers















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      Electrical problem 120-130 1967

      Thanks for the info - I'd prefer to stick with the dynamo instead of the alternator for the moment - I'm trying to keep the car original.

      I retraced my steps and having disconnected the dynamo from the regulator, I checked the output from D+ - it's negative - if I run the voltmeter between the positive terminal of the battery and the dynamo D+ terminal I get 14V. I tried re-polarising the dynamo by again passing a cable between the positive terminal of the battery and the DF terminal of the dynamo but still get a negative reading. What am I doing wrong?

      Thanks for your help,

      Aidan








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        Electrical problem - problem solved... 120-130 1967

        I managed to re-polarise the dynamo by connecting DF to D- to battery negative and D+ to battery positive and running it as a motor briefly. Everything seems to work as it should now.

        Thanks Greg and Ron for your help - Ron, I'll be in touch re some of the things that you supply.

        Aidan







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