OK, here is the deal, I have a Jeep (chrysler) alternator on my 3100 carbed swap. This is because they can be mounted without using a bracket on the engine and they mount down low to clear headers. They are an "isolated field" type, so they use a little regulator, they are very simple to hook up. The thing works great, charges like it should and the volt meter reads right. Wondering if there is some way to make the red light work also with this setup. Larry

I'm not sure how that alternator works with the Fiero circuitry, but pre-88 Fiero, the BAT light in the amp meter display was a part of the charging circuit. If the light burned out, the alternator couldn't charge the battery.

This setup does not use the light for charging, it has it's own little regulator seperate from the alternator. The battery volt meter works fine, it would be nice to have the red light work also, but I don't know how I would do that or how it is wired in. Larry

Grab an Arduino Uno. Add a 7805 5V voltage regulator to run it. Also add a 5v micro relay for the output for your light. Then just two more resistors, one 1K the other 4K to give you a 5:1 voltage reduction and use that as your input.

Program the Arduino to double wink the volt light when you first turn the key on as a nice touch.
Program the Arduino to light the light at under 13v or over 15v
Program the Arduino to flash SOS in Morse Code on the light at under 12v or over 16v

http://www.ebay.com/itm/UNO...&hash=item3cd0d45931

You can mount the circuitry on an arduino development shield

[This message has been edited by phonedawgz (edited 09-08-2013).]

If your alternator has an field output circuit (example: Output pin "L" on a GM, CS type alternator), then the light can be wired with that output.

You need to find out what Jeep did to wire it in their vehicles and duplicate it in your fiero. Do you have the pin-out of the alternator you are using?

-Dave

quote Originally posted by IFLYR22: If your alternator has an field output circuit (example: Output pin "L" on a GM, CS type alternator), then the light can be wired with that output. You need to find out what Jeep did to wire it in their vehicles and duplicate it in your fiero. Do you have the pin-out of the alternator you are using?

Yup... Need Jeep book or Alt doc's to see how that Alt is wired. Shouldn't be hard to dup that.

quote Originally posted by phonedawgz: Grab an Arduino Uno... Also add a 5v micro relay for the output for your light.

Arduino? A bit of overkill... SOS when over 16v is good.

A simple transistor will drive 12V bulb... 194 draws 0.27 amps.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

The Arduino is good idea, I use them for a lot of other things, I will have to look up how the jeep does the idiot light, but my volt meter works good now. The field is just two terminals on the alternator, they are isolated from ground, you just send power through them to make the alternator charge, you can send it either direction. it uses a little regulator that switches one side to ground to get power through the field, it is very simple and nice to work with, but I don't think it is compatable with the way the Fiero light is set up. Not really a big thing not having the light, but it would be nice to tell if you broke a belt or something like that. Larry