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Scalded Cat
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1,847 Posts
Discussion Starter #1
Hi Ed,
Wondering if you could answer a question for me? We wrapped up pretty much all of the wiring on my car yesterday (my brother and I). The only thing we didn't understand is how the red light on the dash gets wired in to the painless harness so the light will light up when the alternator isn't charging properly. Painless wire # 914 is the alternator exciter, according to the painless book. We have #914 wired to the green/red wire from the ford 6 wire alternator as was explained in a post I made last week. We need detailed instructions of how the red light gets wired into #914 and also how the 500 ohm resistor gets wired up. If we can get this one part done and do some testing we should be able to fire it up this next week and go for a go-cart ride .
Thanks in advance,
Todd
 

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FFCobra Craftsman
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3,806 Posts
Since the #914 wire is called the "alternator exciter" wire by Painless, I assume that it has power with the ignition switch in run and no power with the ignition switch in off. If that is true, cut the #914 wire and splice the red light onto the two ends you create by cutting the #914 wire. Also attach the resistor to the same two ends of the #914 wire. When you are done you should have two possible paths for power to get to the LG/R wire at the alternator:
1) 914 to the light, through the light, 914 to the LG/R wire at the alternator.
2) 914 to the resistor, through the resistor, 914 to the LG/R wire at the alternator.
 

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FFCobra Craftsman
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3,806 Posts
If you want the light to light when the alternator is not charging, you have to use a relay.
The Mustang had a alternator failure indicator light. It did not use a relay. If you are using the stock 6-wire Mustang alternator you do not need a relay to operate the fail light. The light needs two things:
1) 12V...... from any switched source (hot in run)
2) Ground...... applied by the alternator to the LG/R wire when the alternator is not functioning
 

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Scalded Cat
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1,847 Posts
Discussion Starter #5
Paul & Don,
I am using the Ford 6 wire alternator that came with my engine new from Gordon Levy. If I understand correctly if I were using a 1 wire alternator that did not have the built in regulator then I would need a relay as described above. Since I have the 6 wire one though I won't need the relay and can just wire in the light and resistor as described. Thanks a ton for the detailed information.
Todd
 
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