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.

 

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.

 

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.

Well hell.... That would be too easy... ... 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.

 

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

http://forum.allaboutcircuits.com/showthread.php?t=54400

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