hooking up an alternator, question

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hooking up an alternator, question

Post by myp71 » Mon Jun 20, 2005 10:43 pm

Wow Hey guys I haven't been on here in a long time. I have been working on building my own generator out of a gas engine and a alternator.I'm using a new alternator out of a 70's chevy 42 amp output. I'm having trouble with my regulator on how to hook it up. Other people have told me that one wire goes to the dash light but they said that I could just hook up a diode and it would make like there is a light connected and then the the other small wire goes to 12vdc.Then of course battery or output wire.When I hook it up like that I get more than 18 volts out of the alternator, so playing around I hooked both of the small wires together and I'm getting 15-16 volts. the 15-16 volts I'm getting out of the alternator is still too much to run my power inverters,so really I was wanting to know if anyone would know if I have it hooked up right,or do I need the alternator to charge a battery and then run my inverter off of the battery? I was really hoping for a circuit that would regulate the voltage more so the alternator output would be less. I know this might not be a question for nuts and volts forum but I have googled just to find no help and I know there are some smart people on here. Thanks for your help

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Re: hooking up an alternator, question

Post by HighFrequency » Tue Jun 21, 2005 6:43 am

This is just a guess.....<p>A diode will not emulate a lightbulb. You need a resistor in there. Unless the dahlight is normally an LED, which (from a 1970's vehicle) I doubt. I know nothing about the automotive world, but that makes sense to me.
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Re: hooking up an alternator, question

Post by Newz2000 » Tue Jun 21, 2005 8:20 am

A VW beetle my brother and I are working on has a generator instead of an alternator. It puts out voltage that is dependent on RPMs, so the VW has a "regulator" which keeps the voltage in proper range for the electrical system.<p>I don't know if that's any use to you. At 2,000 engine rpms the generator puts out about 16 volts but measured at the battery it's a solid 14.5.

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Re: hooking up an alternator, question

Post by gerty » Tue Jun 21, 2005 8:21 am

Looking at the alternator from the BACK you should have the battery terminal(stud connection)
then on the side terminals 1 and 2 of regulator.
#1 is 12 volts and #2 field excitation thru the dash bulb. I have used a diode and tied it to the ignition coil. The field cannot be connected directly to battery as it is a constant load and will drain the battery..
The reason for using a diode when connecting to the ignition coil (+) is that when the key is shut off there is still 12v back feeding from the alternator and motor wil not shut off..
You should expect to see about 14-15 volts, from alternator depending on load..
Hope I haven't confused you too much..
There is a 1 wire regultor available for these alternators (JC Whitney) connects alt to battery..
[ June 21, 2005: Message edited by: gerty ]<p>[ June 21, 2005: Message edited by: gerty ]</p>

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Re: hooking up an alternator, question

Post by Chris Smith » Tue Jun 21, 2005 8:52 am

The light bulb in the dash is a field initiator and indicator. When you first turn on the key, a 12 volt signal flows through the bulb and onto the field windings. This does two things. First the bulb being lit tells you have no charge from the alternator, second it runs a small current into the windings so then when the alternator starts to spin, the field windings are energized, and thus it starts to produce a magnetic field on its own.<p> With out a magnetic field in the windings produced by a current flow from this bulb, or the presence of a permanent magnet, the field windings would produce zero current. Some self starting alternators incorporate a small magnetic to do just this. <p>Once the field windings start to spin, a magnetic field is produced, and so much so that it now creates it own current and flows back wards down this same wire, producing TWO positives at the light bulb leads, thus shutting off the light bulb and representing that the alternator is fine or is producing its current. <p>A diode on a ignition switch will do the same as long as it flows towards the alternator to energize it, and if your producing over the 13.8 volts to 14.2 volts, [under a slight load] then your voltage regulator is defective.

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Re: hooking up an alternator, question

Post by dacflyer » Sat Jun 25, 2005 7:55 am

most alternators will not work right without a battery in the system,,the alternater has nothing to use as a reference...and this can destroy the alternator regulator too in time.. is this a self regulated alternator? if not then you will need a regulator too.. hope this helps ya

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