adding a charging fault light

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moparmat2000 said:
If on a typical alternator , the sense wire is needed with the resistance of a light bulb to get the regulator to start charging, couldent you run a 14 ga wire with a 470 ohm 5 or 10 W resistor to make the alternator think its a light bulb, , then if you wanted an LED indicator light, just wire it in parallel to the resistor with the negative side of the LED going towards the alternator. Since they only light in one direction polarity wise wouldent a setup like this work. I mean some of y'all are talking about diodes. Rectifiers, relays etc to make the light come on and go out. Do you think maybe your over thinking it a bit, or am i just under thinking it.

Matt
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I would have to think that through, but it could work.
LED is off when power is flowing out of the alternator and lights when power is going out of the battery.
That could work, and it would take some real world testing to find out for sure.
 
BUT mopars dont use this kind of a setup. A voltage reg is a simple switch that turns voltage on and off to field on ALT. Unless we are now talking changing to a different system? Im thinking about those of us who want to keep mopar stuff.
 
Mopar Tim said:
BUT mopars dont use this kind of a setup. A voltage reg is a simple switch that turns voltage on and off to field on ALT. Unless we are now talking changing to a different system? Im thinking about those of us who want to keep mopar stuff.
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I am talking about general alternators. If it requires a sense wire with a light, but you intend to use a an LED for your light, just run a sense wire with a resistor of the same or similar characteristics as the bulb it replaces to fake the voltage regulator into thinking you have a bulb. A resistor will take voltage both directions like a light bulb. Then wire your 12v LED in parallel to the resistor, with your normal 12v feed coming from an ign switched hot. Id say since the volt gage is ign switched hot, and the fault light is there, attach your sense wire to the + side of the volt gage stud and feed it to the voltage regulator sense connection.

The nice thing about doing it this way especially with a denso alternator is the LED will light no problem with key on, or with an alternator failure causing a ground. At least thats the theory. LOL
 
67Dart273 said:
They work essentially the same as a 70/ later Mopar, and in fact you can wire up a 70 / later Mopar regulator instead of the pcm.

https://alternatorparts.com/external-voltage-regulator-high-output-alternator-kit.html
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Ditto. Same deal in my 1996 Voyager and I recall in my 2002 T&C. The alternator field is the same "isolated, 2 terminal" design as in 1970-80's Mopars, just a different connector. One terminal gets IGN and the other is shunted to GND to control the field (low-side control). Problem is that Vreg control is integral w/ the PCM. But, as 67Dart273 mentioned, many clever people have figured to just intercept the wires and control w/ an external Vreg (1970's). I wouldn't hack the factory harness, but just unplug it and use a connector from a junkyard vehicle (many there now), wired to a nearby Vreg.
 
You guys are talking about several different types of alternators all of which are wired differently. The Denso alternators have a warning light circuit that is not part of the excitation circuit. The alternators that use a light or resistor for excitation have a warning light or field circuit for excitation. The sense circuit is not used for excitation or warning it is used for the alternator to monitor battery voltage.
On the old Mopar alternators, there is no circuit for a warning light. If you are an electronic hobbyist, or know one, There is a real simple circuit that can be made using a 741 Op Amp as a voltage comparator that will turn on an LED at a preset voltage. You can set it to turn on the light at any voltage you want. I used to have one set for 12 volts. If your battery is at 12 volts, your alternator is dead. Sorry, I can't find my schematic, but if you Google 741 Op Amp you'll find plenty of them. If you've ever built an electronic project, you can build one of these.
 
Thats great info for guys wanting to do this and not use a denso. Personally i like the mini denso. Its a lightweight cute little powerhouse. Easy to wire, and for those who dont have the ability to make their own brackets, theres companies that make the brackets.

The fault light doesnt need to be a bulb, but can be an LED, or that part of the plug (L terminal) can be left unused , only the IG part of the plug needs to be wired
 
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