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Discussion Starter · #1 ·
I had problems with my alternator light on my dash flashing at me for while. I wrote it off as a faulty light because it would flash when I hit bumps. I was in the parts store parking lot when the battery gave up the ghost. So I replaced the battery and alternator (using the v-belt pulley from the original alternator because the new one, which was a remanufactured one, came with a serpentine pulley). I continued to see it flash at me going down rough roads. Come to find out, my voltage regulator connection was loose. I replaced it with a new voltage regulator and didn't see any problems. It has started flashing again, but this time only when I am going faster than 55 mph. Could this be the pulley slipping? If not, what could it be?
 

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I've been having a similar problem on the same car. I completely rebuilt my alternator, bought a brand new battery, I haven't changed the voltage regulator yet but it's on my to do list. My alternator light just keeps flashing, although it's always on and flashes when in park and when idling.
 

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Discussion Starter · #7 ·
Mine appears to be securely connected to the fire wall and the manifold. I will replace the wire and see if that makes a difference for chance of corrosion. I currently have my exhaust taken apart awaiting some headers. Once I get that squared away and replace the wire, I'll see if it helps any. Thanks for the help everyone.
 

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Ok. I attached the body ground wire to the manifold. That didn't fix my problem. I then bought a brand new Voltage Regulator, and that sort of fixed my problem. Let me explain, it solves my problem when it's not mounted. In other words, as soon as I mount the regulator to the body of the car my alternator light lights up. When it's not connected and just hanging in mid air not touching anything it works just fine. Can anyone plz help!?!? I also replaced the body ground wire with a brand new one.
 

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Hey, just found this old thread so pulling it back up. I'm having the very same problem with my 68. ALT light blinks in a steady pulse like a metronome. If any accessories are on (lights, heat, AC) there is no flashing. I assumed it was a bad voltage regulator or just a bad diode so purchased a new regulator (the expensive kind). With the new regulator on the ALT light is on all the time when it is screwed to the frame. If I wiggle the connector I can get it to go out for a while but it will come back solid red eventually. When I let it hang (not connected to the car body) I don't get the solid red light. So I switched back to the old voltage regulator assuming it was a bad connector (it fits very loosely) and just keep something on all the time to avoid the flashing. I'd sure like to figure out why I'm getting the flashing.
 

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Hey, just found this old thread so pulling it back up. I'm having the very same problem with my 68. ALT light blinks in a steady pulse like a metronome. If any accessories are on (lights, heat, AC) there is no flashing. I assumed it was a bad voltage regulator or just a bad diode so purchased a new regulator (the expensive kind). With the new regulator on the ALT light is on all the time when it is screwed to the frame. If I wiggle the connector I can get it to go out for a while but it will come back solid red eventually. When I let it hang (not connected to the car body) I don't get the solid red light. So I switched back to the old voltage regulator assuming it was a bad connector (it fits very loosely) and just keep something on all the time to avoid the flashing. I'd sure like to figure out why I'm getting the flashing.

Hello bowdidge,

The most likely cause of the alt lamp flashing is the alternator. Here's why if you're interested; the "ALT" lamp is turned off by stator voltage on the "S" terminal of the voltage regulator which is generated by the alternator so the "S" terminal on the regulator is an input. By your "old voltage regulator" I would infer that it's the mechanical type (large domed cover). The stator sense is nothing more than a high inductance high permeability relay. It's rather sensitive and even low stator voltages will trigger it, verses newer electronic regulators which typically have a higher set point trigger voltage needed to switch off the lamp withcidentally when the lamp is turned off by the voltage regulator on the old mechanical type the field current is supplied directly from the battery and not through the lamp as when the lamp is illuminated.

I almost want say check the "S" wire that goes from the regulator to the back of the alternator, but the ALT lamp goes out when there is a heavy load. There's a slim chance it could be a loose/dirty connection or defective wire and of course all connections should be cleaned and tightened. You can remove the terminals from the voltage regulator plastic socket via a small tang that when depressed off the back side of the terminal will allow it to slide out (same as a Packard type 56 GM connector). Once the individual terminals are out, you can gently squeeze the sides slightly with duck bills to increase the retaining friction and put back together once cleaned.

There's a higher probability that the problem lies within the actual alternator in the form of shorted or possibly open turns on the stator windings or leaky and or open diodes on the 3 phase bridge inside. Since the stator voltage to the regulator is derived from the centre tap of the wye of the stator windings, if one phase/leg has shorted turns then only when the alternator is driven hard (all accessories on) does voltage in the centre of the wye rise enough to keep the relay in the old voltage regulator energized constantly and hence the lamp stays off.

If this is indeed the case, the alternator is putting out, but is only capable of putting out a fraction of it's rated current under load. Easiest way to test this is take it in to a place that can spin test the alternator under rated load on a good machine.

One last note, the voltage regulator needs to be grounded to work hence the independent ground lead coming from the alternator itself that uses one of the fasteners on the regulator body.

Hope that helps.

Good Luck.
 

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I have a similar problem with my 1970 Galaxie. I am using a Delco 12si and I decided to try and run my own idiot light for my car. So I run a jumper to the wire running from the alternator to the battery. So on the other wire that I will be using for the light. I run a wire from the alternator to inside the car and connect to one side of the idiot light. I can't find a place to tie into the other side of the idiot light to complete the circuit. Any suggestions would be appreciated.

Sent from my XT1575 using Tapatalk
 

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I have a similar problem with my 1970 Galaxie. I am using a Delco 12si and I decided to try and run my own idiot light for my car. So I run a jumper to the wire running from the alternator to the battery. So on the other wire that I will be using for the light. I run a wire from the alternator to inside the car and connect to one side of the idiot light. I can't find a place to tie into the other side of the idiot light to complete the circuit. Any suggestions would be appreciated.

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Hello jhayes91,

So on the 12 SI Delco you can actually use the galaxies ALT lamp if you wish. GM and Ford used the same warning lamp circuit. But since you have your own lamp wired the other side of the warning lamp should be tied to IGN positive or Accessory positive. You can even use the switched radio feed if it's handy.

Just to make sure, you have position 1 of the 2 wire plug of the alternator (white or brown) that goes to the interior warning lamp and position 2 (red) goes to the battery or common Batt + tie point in the car, in the galaxies case it's usually the starter relay lug leading to the + on the battery. And of course the large heavy cable on the main terminal on the back of the alternator also going to either directly the battery + or the same lug on the starter relay.

Hope that helps.
 

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Hello jhayes91,

So on the 12 SI Delco you can actually use the galaxies ALT lamp if you wish. GM and Ford used the same warning lamp circuit. But since you have your own lamp wired the other side of the warning lamp should be tied to IGN positive or Accessory positive. You can even use the switched radio feed if it's handy.

Just to make sure, you have position 1 of the 2 wire plug of the alternator (white or brown) that goes to the interior warning lamp and position 2 (red) goes to the battery or common Batt + tie point in the car, in the galaxies case it's usually the starter relay lug leading to the + on the battery. And of course the large heavy cable on the main terminal on the back of the alternator also going to either directly the battery + or the same lug on the starter relay.

Hope that helps.
Yes, I am having trouble trying to find the right wire under the dash to tie into. The previous owner removed the voltage regulator out under the hood, and I can't find the old wires out under the hood to tie into.

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Yes, I am having trouble trying to find the right wire under the dash to tie into. The previous owner removed the voltage regulator out under the hood, and I can't find the old wires out under the hood to tie into.

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Hello again,

Sooooo you mentioned you had your own warning lamp, but it kind of sounds like you were trying to find the original warning lamp wiring under the hood to use. Which do you want to pursue?

If it were me I'd want to use the cars original for two reasons, probably looks nicer than a generic one and you don't have to monkey with under the dash wiring.

I am not too familiar with the 4th gen galaxies, but my friend has a junk '71 Custom in his back yard. If I remember right the voltage regulator is in the same spot as the later 3rd gen's, which is behind the battery on the radiator support. Although on the 3rd gens the wiring come down the passenger side apron. I can't remember where the harness came from on the '71 Custom.

But usually the alternator lamp was tethered to the same wiring bunch as the main cabin feed and the starter relay trigger wire (start). Find those two in the engine compartment and I bet you'll find a straggler wire for the alternator lamp. It's usually green with a red stripe or something similar.

Let us know how it goes.
 

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I'd be fine if I can get the original one working. The voltage regulator has been removed. The harness for It is gone too, but I think where it exits the firewall on the engine bay side is still there. I need to look closer,the whole harness could be there, just tucked away in the corner by the hood hinge. I'm going to post a wiring diagram, and I'll say which wire I think I need,and if you don't mind look and see what you think.

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Going by both diagrams, I'm thinking I need to find the 904 wire (green wire with red strip)
 

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I'd be fine if I can get the original one working. The voltage regulator has been removed. The harness for It is gone too, but I think where it exits the firewall on the engine bay side is still there. I need to look closer,the whole harness could be there, just tucked away in the corner by the hood hinge. I'm going to post a wiring diagram, and I'll say which wire I think I need,and if you don't mind look and see what you think.

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Going by both diagrams, I'm thinking I need to find the 904 wire (green wire with red strip)
Yuppers circuit 904 on the bottom diagram, green with red stripe. Like I mentioned earlier it usually travels with the same wires for the main cabin feed and starter relay trigger wire. They couldn't have cut all that, otherwise the car wouldn't start and there would be no power.

Best bet is to locate the starter relay and follow back the large and smaller wire leading off the relay towards the firewall, the little green wire should be in there or very close by.
 
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