Voltage Regulator

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Apr 1, 2014 | 12:42 PM

cyris426

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Joined: Sep 2012

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Voltage Regulator

Hey guys I have a 1984 rx7 that I put a 1975 ford maverick 5L into. I have got it running and have drove it and stuff. However I am struggling with how to make the charging system work. I currently have the voltage regulator set up along with the alternator that came with the engine. I will outline how it is connected.

I – this wire is green and from what I understand it is some sort of idiot light for the gauges. I have no idea about this one and so I have so far left it unwired. Could this be my problem?

A – There are two wires that come out of here. They are both yellow. One has a connection you can undo and the other side of the connection connects to a little metal cylinder that has a bolt hole on it. I think this is some sort of radio suppressor or something. I have it hooked up and bolted to the body. The other yellow coming out of A connects to a black junction with two black orange wires coming out of it. One goes to the back of the alt in the factory grommet and the other goes to a fusible link I installed which connects to the positive side of the starter relay (the side that is connected to the battery)

S – So this one is white and it also goes to a black junction box. One side goes to the alternator grommet, the other I have connected to the automatic choke on the carburetor.

F – This last guy is orange and it connects to the alternator black grommet.

The wires that connected to the alt were cut when the guy had removed the engine so it has hard to get the connections wrong when I reconnected them since they are color coded and there are only three wires coming from the back of the alt. One is black/orange, one is orange, one is white, or at least a creamy lighter color.

I think I have everything connected correctly. Yet when I turn the engine on I cannot see the voltage gauge move past 12v like it would on a normal car with the engine running and the alternator running. The belt is connected and everything.

So what’s the deal? Could the alternator or voltage regulator be bad? Is it wired incorrectly?

Thank you
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Apr 1, 2014 | 01:08 PM

fmc400

MSEE

Joined: Apr 2004

Posts: 10,386

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From: Austin, TX

Quote:

Originally Posted by cyris426

I – this wire is green and from what I understand it is some sort of idiot light for the gauges. I have no idea about this one and so I have so far left it unwired. Could this be my problem?

If you intend to operate the system with a charge light, the 'I' terminal connects to keyed power "through" the charge light with a shunt resistor in parallel with the light to allow current to continue to flow in the event the ALT light burns out. I don't recall if the resistor is 510 or 560 ohm, but it does need to be able to dissipate power in the presence of ambient temperature rise. Use a ceramic power resistor.

If you do not intend to operate the system with a charge light, leave the 'I' terminal unconnected. Instead, run keyed power to the 'S' terminal, but you must change how you have the 'S' input wired. More on that below. Based on your description for how the 'S' terminal is connected, yes, leaving the 'I' terminal unconnected will prevent the system from charging. There's not much point in having a charge light anyway if you already have a voltmeter.

Quote:

Originally Posted by cyris426

A – There are two wires that come out of here. They are both yellow. One has a connection you can undo and the other side of the connection connects to a little metal cylinder that has a bolt hole on it. I think this is some sort of radio suppressor or something. I have it hooked up and bolted to the body. The other yellow coming out of A connects to a black junction with two black orange wires coming out of it. One goes to the back of the alt in the factory grommet and the other goes to a fusible link I installed which connects to the positive side of the starter relay (the side that is connected to the battery)

The metal cylinder is an ignition noise suppression capacitor for the radio as you describe. Its connectivity is inconsequential. The 'A' terminal is the sense input of the regulator and must connect to the alternator output. Assuming the wire coming out of the junction that goes to the alternator goes to the large alternator output stud, then it sounds like you've got this set up correctly.

Quote:

Originally Posted by cyris426

S – So this one is white and it also goes to a black junction box. One side goes to the alternator grommet, the other I have connected to the automatic choke on the carburetor.

If you do not plan to run a charge light and leave the 'I' terminal unconnected, do not connect the alternator to the 'S' input of the regulator in any way. Run only keyed power to the 'S' input of the regulator. The alternator 'STA' stud runs to the electric choke only. There is no connectivity between the alternator 'STA' stud and regulator 'S' input in this case. If you DO use a charge light, then the 'STA' stud of the alternator connects to the 'S' input of the regulator, but then there is no keyed power connection to the 'S' input of the regulator (only the 'I' terminal of the regulator through the charge light). It sounds like you're using an alternator harness for a charge light setup, but connecting the regulator as if no charge light is present. Note that tying keyed power to the 'S' input without disconnecting the 'STA' output of the regulator will result in an electrical fire.

Quote:

Originally Posted by cyris426

F – This last guy is orange and it connects to the alternator black grommet.

The 'F' output of the regulator runs directly to the 'FLD' stud of the alternator no matter what you do with a charge light. Make sure this connection is being made in the harness you're using.

Quote:

Originally Posted by cyris426

Is it wired incorrectly?

Yes.