Thread: Alternator Idiot Light!

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Yesterday, I converted my test motor stand over from a push button/toggle set up to a Turn Key w/fuse box set up. Only reason I did this was to improve upon my knowledge as the old set up was just fine. Good news is everything worked like a charm! Only exception was my alternator idiot light. For kicks, I wanted to wire an idiot light up and when I had the motor running, the light stayed on (I had 10V while running but this is a test motor setup and not a car so battery was probably a few volts low anyhow). Can you look at my wiring diagram below and let me know if it looks right to you? If it does look right, what are my next steps? Thanks!

Here's a pic if you can't open attachment.

FYI, I did not show it but my battery wire is routed to fuse block and from there to 'batt' on turn key. So it looks like my idiot light is correctly wired looking at your diagram. So are you saying the light is supposed to be on at all times, and when it goes out then you have a bad circuit? I thought the light was supposed to be off and only supposed to come on when you had a problem as in alternator not working. I had things reversed in my thinking?

Few other questions on the diagram:
1. The main battery wire from alternator is going to the fuse block ('battery fuse?'). Mine is routed direct to battery. Does it matter either way or is one preferred over the other?

2. The diagram shows #2 exciter wired back to the fuse block and I had mine wired to main battery line on alternator. Does in need to go to 'battery' fuse on the block?

Per the diagram, I'll rewire the main battery wire and run it to the fuse block instead of direct to battery (I'm assuming 'batt' fuse). I'll do the same with the #2 exciter wire and run it to the fuse block instead of jumping it in with main battery wire off the alternator and see if that makes a difference.

Denny, as usual, is right on the money. If the voltage is fairly equal on either side of the light it will stay off. If the light is on it means there is a difference of voltage from one side of the light in reference to the other (potential difference) which creates current flow and the light illuminates.

Denny, I got to looking at this again and see that I did not wire idiot light, like the diagram shows. I wired light to IGN fuse on block terminal. The diagram shows the light wire running direct to IGN on switch. Will try it.

Ok really need some help unless i can figure this out in next hour before i call it a day. It seems i've got bigger problem than idiot light. Came into shop this anoon and had less than 1 volt on battery. Put battery charger on it for 5 minutes and charger showed full charge. Disconnect my jumper wire from term 2 and instantly battery showed correct voltage. Without idiot light hooked up, tried running main battery wire from alternator and term 2 wire to fuse block on the 'Batt' fuse like diagram suggest. Put multi meter on there and literally saw the volts drain away fast..... This does not seem like rocket science. On my old push button toggle system i had the alternator main wire to the battery and term 2 wire to a toggle switch that controlled my coil and had no problems.. Any ideas lol?

Edit: I rewired the alternator as a one wire deal and did not hook up/touch terminal 2. Did hook up idiot light and with car running the light did not come on. Still going to monitor and tinker with tmrow anoon as i'd like to get term 2 straightened out. What i don't get is that my multimeter showed 11.5 volts at battery, when motor was running and also off but the volt guage only showed 9.5 when running...Also, i don't see as how i have a parasitic draw problem either since that's on my mind considering i had no juice today. I've only got a 5 fuse block and the only term that stays hot all time is the one battery fuse (battery lead feeds this fuse and another wire to 'batt' term on switch), i dont have anything running on other end of fuse. Perhaps will draw a sketch of my simple wiring diagram.

Wanted to give DENNYW a Huge shout out and say Thank You! Denny's advice, thoughts, and provided information served me well in tracking down this problem. I found out it was never the idiot light that was my problem. The irony was that I wired the idiot light right and it was trying to tell me, 'hey you've got a problem.' I've learned way more about alternators than I ever thought and through Denny's help, learned how to take one apart, run diode tests, etc. As it turned out, I had a diode that would not flow in one direction (passed diode test but would not register an OHM value like the others). Had another alternator of the same type, put it on there, and no problems. Testing for parasitic draw goes a long way and I wish'd i had of done that immediately when my problem started. But hey, its been a learning experience Thanks Denny,