Can a fiero alternator be ran backwards? If so, do I need to do anything special to make it run backwards?

Thanks

fan blade is backward. Thats really about it. I hope you aren't going to try to drive the alt off the smooth of the belt... I assume you mean you are putting an alternator so the case is on the opposite side of the engine.. It'll work, but still the fan is backward.

Oh no, what are you doing? You need room for something down there.

What he said about the fan. I dont know where you would find a fan, But you may want to start with marine applications. I know they run in reverse rotation on some applications with twin engines.

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get one with a metal fan and not that **** plastic one - then you can bend the fan tabs backwards and flip it over

wait - shouldn't a guru already know the answer?

[This message has been edited by Kohburn (edited 03-18-2005).]

I dont know this for a fact - just going on what I know of electric motors.
electric motors have "timing". it has to do with the creating & collapsing of the magnetic fields that make it go. since a alternator is basicly a electric motor, backwards, I would expect there is "timing" in an alternator also. and, if there is, then when its running backwards, it output will be much lower, and its output will be reversed.

Thanks for the info.

The Paxton/Procharger kits for C4 vettes have the alternator running backwards, they my have everything I need.

quote Originally posted by Pyrthian: I dont know this for a fact - just going on what I know of electric motors. electric motors have "timing". it has to do with the creating & collapsing of the magnetic fields that make it go. since a alternator is basicly a electric motor, backwards, I would expect there is "timing" in an alternator also. and, if there is, then when its running backwards, it output will be much lower, and its output will be reversed.

I believe an electric motor starts by itself, while the alternator is run by the engine. I don't know what to say about the output being reversed- would it take the voltage out of the battery and store it in the alternator? Or maybe the amperage.
The alternator doesn't care which way it is going, just the blades that circulate the air through the case.

I don't know about the timing, but I can tell you that the output would not be reversed. An alternator generates an AC current when it is spinning, so the voltage is constantly reversing polarity when it is running. Six diodes are used to convert the AC to DC. If you run the alternator backwards, the diodes will still cause the current to come out with the same polarity.

quote Originally posted by gunnie: I believe an electric motor starts by itself, while the alternator is run by the engine. .

right. take a DC electric motor, and turn it, it becomes a generator.

quote I don't know what to say about the output being reversed- would it take the voltage out of the battery and store it in the alternator? Or maybe the amperage..

with DC, you have a (+) and a (-) line. reverse would be what is normally the (+) is now the (-)

quote The alternator doesn't care which way it is going, just the blades that circulate the air through the case.

no, it doesnt, I was just saying the output may be lower, and maybe reversed. but, being I beleive the alternator generates in AC, and not DC (hence the name Alternator, not Generator?) the voltage regulator will control the (+) & (-) outputs properly.

My brother in-law has ran his alternator backwards on his race car for years. He hasn't seen any ill effects because of this. Of course it is a big-block Nova and doesn't have the heat related issues we have with our cars. The fan on the alt. seems to be the only thing that would keep me from doing it in this application.

Richerd

I think you have lost me. Why do you want to run it backwards?
Don

It will work fine either way. Just go to the wrecking yard and get a fan pully that has the blades in the other direction, GM runs them both directions.

The diodes in the alternator convert the AC sine wave into pulsating DC, that is differant than an alternator that is positive ground (that can be done too, but another story).

"Timing" of an electric motor can be adjusted in some motors, but generally they are set at "brush neutral" so they run just as efficient in forward or reverse. This is not an issue here though because this is an alternator and not a generator.

SO does that mean you would have to run the system with a + Grounding system??? I thought GM did that back in the 70's hehehe

No it does not.

I'm going to have to come down and see what you are up to again.

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If you run it backwards it will suck all of the amps out of the car.

quote Originally posted by Jim Krause: If you run it backwards it will suck all of the amps out of the car.

If you wanted to test this you could drive the car in reverse for a few miles and see what happens.

On changing the fans... It depends what alternator.... The SI you can probably fix/make a fan that will have the right blades for reverse rotation. The CS units would likely have to be taken apart as there is one of more fans inside them depending on what version it is.

Nearly all alternator fans have the blades set to optimise flow in their "forward" direction and spinning backward will cut air flow significantly. Depending on the fan it may flow almost nothing spinning backwards.

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