1 Wire GM Alternator and Generator Light

Discussion in 'The Projects Forum' started by Budman1758, Nov 20, 2013.

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  1. Budman1758

    Thread Starter New Member

    Nov 20, 2013
    Searched most of the forums here and did not find an exact answer to this one. I have and old vehicle and have installed a newer 1 wire GM alternator in it. These alternators do not have provision for the "idiot" light on the dash. What I am looking for is a simple circuit that will trigger a relay to operate the light. I want it to light at just under 13 volts and go out at just over 13 volts. (or thereabouts)

    I had thought I could just use a 13v zener diode but it seems to require a little more than that. I tried to put the zener inline thinking it would conduct "backwards" when the voltage went above 13 volts but it seems they don't work quite like that. There is an outfit that sells something exactly for this purpose but the voltage is set at 11 volts and they want 30 bucks and 10 bucks to ship the darn thing. Diodes are much cheaper. :>)

    Anybody have a simple circuit in their back pocket that will do this? Any help would be much appreciated.
  2. bwilliams60

    Active Member

    Nov 18, 2012
    Why don't you spend less than 10 bucks, go to a rebuilder and get the proper voltage regulator for it and turn it back into a three wire. Takes less than an hour to convert it. I can walk you through it.
  3. Budman1758

    Thread Starter New Member

    Nov 20, 2013
    Well hell.... That would be too easy... :rolleyes: ... Actually, I just didn't think of that. I was going to revert to 3 wire whenever the alternator failed. I know how to do the conversion. Probably gonna look into that.

    Thanks for the quick reply.
  4. Wendy


    Mar 24, 2008
    The owners of All About Circuits has elected not to host discussions of automotive electrical system modifications/enhancements due to safety concerns, the potential of legal ramifications and the possible circumvention of vehicle regulations at the state and federal level.

    This thread is against the AAC forum rules, Chapter 6, as seen here:

    This can be found in our Terms of Service (ToS)

    Automotive modifications of any kind are strictly forbidden. Therefore, this thread will be closed.

    Please try to understand the reasons behind this action, and feel free to browse and use the forums.

    You might find answers to your questions in one of these forums:


    Another good forum that shares many of the same membership is http://www.electro-tech-online.com/ . Good luck.
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