Is my Alternator wired wrong?

[48richard]

My internally-regulated alternator works (it keeps the battery charged), but the generator light has never worked since I bought my truck.

I believe the blue wire, which is connected to the brown wire from the bulkhead connector, should be connected to the left hand terminal (looking from the back) not the right hand one as it is now, and there should be a jumper from the right hand terminal to the battery connection.

What is confusing me is that I have read that the alternator will not work without 12v on that left-hand (#1) terminal, but there's been nothing there for at least the 2 years I have owned the truck.

Any ideas?

[JimKshortstep4x4]

The wire from the ignition switch should be hooked to the no.1 terminal on the alternator. The no. 2 position on the alternator should be hooked to a 12 volt + source. The number 1 wire on the original wiring is a resistor wire so the voltage will not read much over 8 volts when hooked to the alternator. (The resistor wire runs from the ignition switch to the regulator and is a small brown wire).

It is a good practice to make sure the number two wire has some length to it as you can experience low output of the alternator.

I assume that you jumpered the wires on the regulator plug. I am not sure why the alternator is charging but I have to believe that it is not functioning correctly.

if you hook up the alternator as described and the wiring is correct back to the switch your charging light should work.

Jim

[48richard]

Interesting. I haven't changed the wiring since I bought the truck. There is a jumper between blue and brown at the old regulator connector.
I'll switch it to the correct terminal tomorrow and see what happens

Thanks!

[5150.4.67]

Looks as though you have a 10si 60 amp alternator. The wire on the right is a remote voltage sensing wire, thus should go to the bus bar on the horn relay or some other 12+ volt major junction block. This wire serves to tell the alternator what the voltage of the system is away from the battery where the voltage drops slightly.
The other wire (on the left in your picture) is the wire that runs to one side of a Gen or Alt light (and acts as a resistor) and the other side of the bulb is wired to 12+ ignition power. When alternator is not working or turning, the light illuminates as it is grounded by the alternator.
Most people just run a jumper wire from the 12+ volt output/battery wire to the connector on the right. While this works, it is not optimal and may require the engine to rev above 1500 rpm before it starts charging.
Might as well use the Gen light wire, you will know when it quits working before it leaves you stranded

[48richard]

This is not getting any clearer!

First, I now get why my generator light does not work - I don't have one. Don't I feel like the **** .
Anyway, my battery voltage with the key off is 12.2 - low, but that's another issue.
With the engine running and wiring as shown in the picture, voltage is 14.4, and the ammeter shows on the + side, so the alternator is charging.

When I move the blue wire to the left terminal, the alternator does not charge; same thing if I leave it disconnected.

There is battery voltage at the blue wire with the key on

I connected a bulb from the left terminal to the battery. It glowed dimly with the engine off, and went out with the engine running. The resistance between the left terminal and ground with the engine off is 44 ohms, which explains why the bulb glows only dimly.

As I said, this is not getting any clearer. Anyone else have any thoughts?

[VetteVet]

You may have one of the early one-wire alternators that they used on tractors and other equipment. If so you wouldn't need anything but the large red wire on the back connected to the positive battery or starter terminal. It is possible for a three wire alternator to work without the left hand wire connected because of residual magnetism in the internal fields generating enough voltage to excite the internal regulator. I suspect that the 44 ohm reading means that the diode trio is shorted to ground and will not work as a three wire because the exciter voltage is going to ground instead of the alternator fields. I'll have to check the ohms reading on one of my alternators and see what I get, just for kicks.

[fixit-p]

The reason why it works the way it is wired is because when you apply power to the #2 terminal current flows to the base & emitter of transistors TR3 and TR1 (turning them on) current on terminal 2 also flows to ground through resistors R2 (thermister) and R3. When there is nothing connected to terminal 1 with the engine running there is very little voltage produced by the alternator but if revved up can produce some power. I've recently measured 1.5 volts @ ~1500 rpm with nothing connected to a 10SI other than my multimeter.

In a recent thread board member Stellar stated that the speed at which an alternator can produce enough voltage to self excite is dependent on the air gap between Rotor and Stator, makes sense to me IMO we've basically created static electricity. Now back to why it works, since transistors TR3 and TR1 are turned on. the 1.5 volts of static electricity (for lack of a better term) can now flow through the field winding's and TR1 to ground creating our magnetic field which increase alternator output until it reaches the regulator set point.

If terminal 2 has no power but you apply full battery power to terminal 1 the field windings are now saturated but cannot flow to ground because TR1 is closed that's why you had no output when you swapped the wiring around.

The 44 ohms reading you measured on terminal 1 to ground is low, possibly it was more like 44k ohms. In the diagram below resistor R6 is connected to ground but not all alternators have resistor R6 in those alternators terminal 1 would be open to ground unless power was applied to terminal 2 opening TR3 and TR1 allowing current to flow from terminal 1 through resistors R1 and R4 transistor TR3 to ground. I measured on a 10SI here at work 36k ohms to ground.

What you basically have there is what board member HEI451 and others do to convert 10 & 12 SI alts to 1 wire conversions. But the fact that you have the sense wire connected to an ignition source instead of the battery post on the back of the alternator or better would be an alternator buss. May introduce unwanted resistance into the sense circuit and could lead to over charging.

EDIT My multimeter at work is faulty it was reading 36 on the k scale and not .0036k,

[Curly5759]

Stock set up had the following:
Switched 12v to indicator light to terminal 1 on Alt. Terminal 1 leads to the field windings and then to ground. (The windings were the 44 ohm reading you saw) Key on,Engine off -- power flows through the indicator light to the regulator and then on to ground. This provides 12v to the field windings in the alt. (Field = Rotor ) The resistance of the bulb prevents a full 12v from reaching the rotor. The combination of the bulb resistance and the field winding resistance is why your test light was dim.

Key on, engine running--The stator is now producing voltage, which flows through the diode trio to the connection right below r6 (in image above).
This puts voltage on both sides of the indicator light and it goes out. That is the same reason your test light went out when the engine started.


Curly

[fixit-p]

Originally Posted by fixit-p

The 44 ohms reading you measured on terminal 1 to ground is low, possibly it was more like 44k ohms. In the diagram below resistor R6 is connected to ground but not all alternators have resistor R6 in those alternators terminal 1 would be open to ground unless power was applied to terminal 2 opening TR3 and TR1 allowing current to flow from terminal 1 through resistors R1 and R4 transistor TR3 to ground. I measured on a 10SI here at work 36k ohms to ground.

I must correct myself here, it appears that my multimeter I have at work is bad and was giving me 36k ohm reading and not .0036k ohm. I'm installing a 12SI alt for a buddy and just for kicks I wanted to check the resistance on it because this one has R6 whereas the one at work doesn't. I measured with a good multimeter 42 ohms from terminal 1 to ground and when applying 12 volts to terminal 2 allowing the field windings to go to ground I measured 6 ohms.

[48richard]

Thanks for all the input.
I finally got this re-wired yesterday. I took out the old regulator connector, extended the brown wire up to the #1 terminal on the alternator, and extended the red wire to the #2 terminal to provide remote voltage sensing. From what I have read, just putting a jumper from the output terminal over to the #2 doesn't accomplish anything, since it just duplicates an internal connection. The point is to measure voltage at some distance away from the alternator so it knows the demand under load.
Anyway, the good news is that it works, and at 1000 rpm with lights, radio, and A/C on at max, the voltage at the fuse block has gone up from 13.6 to 14.4 volts.

[VetteVet]

That;s great. Yes it really is that easy to convert to the internal regulated SI alternators. for you folks that need a visual just look below, and follow what he said about the conversion.








Now for those of you who have the battery gauge instead of the idiot light then you will have to maintain the wiring in the diagram below. Go ahead and extend the wires and convert the alternator but you must keep the large red wire on the left aka the shunt and you must wire the large red wire off the back of the alternator to the shunt as shown and the fused wires are the feed wires to the ammeter. One to each terminal of the gauge. The fuses are 4 amp and are there to protect the ammeter gauge. If either one is blown then the gauge won't work.

[dmjlambert]

I have read and read a lot of posts, including the FAQ, and this one seems the best to bring back from the dead for more clarification. I have a 69 CST-10 with a 350 engine and gauge cluster. I currently have the stock wiring and stock externally-regulated alternator, and everything is working, including the battery gauge. I am looking at installing a 12SI alternator.

I have read about connecting the brown wire from the cab to terminal 1 of the 12SI. Inside the cab that goes through a light bulb to the ignition switch. I have also read some posts that talk about a resistance wire. I don't know what I have, but I know I don't have an idiot light for the alternator. In order to properly use the 12SI, do I need to add an idiot light? What if I don't and just connect the brown wire from the cab? I do have a brown wire with white stripe at the ignition switch, is that a resistor wire? Is the brown and white wire to the ignition switch only present on a truck with a gauge cluster? The wiring diagram shows both brown wire to an idiot light cluster, and brown and white wire to the ignition switch, connected to the same terminal in the cab, but that does not make much sense to me that both could be present because it seems the idiot light would not work.

I have read about connecting terminal 2 of the 12SI directly to the output terminal of the 12SI, and that is how I see most online information about the wiring done. But then 48richard brings to question the point of terminal 2 is to measure voltage at some distance away from the alternator. As far as I can find, that is still a question, and I am wondering about it, too. Is tying the red and blue wires together at the regulator connector, and connecting the blue wire to terminal 2 of the 12SI accomplishing this "measuring the voltage some distance from the alternator," or is it just flat out not needed and putting a very short wire from the main output of the alternator to terminal 2 just fine and dandy?

I don't understand the post above where VetteVet talks about "Now for those of you who have the battery gauge instead of the idiot light then you will have to maintain the wiring in the diagram below. Go ahead and extend the wires and convert the alternator..." Well, I have the gauge and shunt wire and fused wires that lead to the meter in the cab, and I don't plan to alter that wiring, it seems to work fine. What does "Go ahead and extend the wires and convert the alternator" mean? Does this mean if we have a gauge cluster and everything is currently working OK with a externally-regulated alternator, the same jumpers should be installed at the regulator and the same connections made at the 12SI alternator as shown in the idiot light diagram?

[VetteVet]

Originally Posted by dmjlambert

I have read and read a lot of posts, including the FAQ, and this one seems the best to bring back from the dead for more clarification. I have a 69 CST-10 with a 350 engine and gauge cluster. I currently have the stock wiring and stock externally-regulated alternator, and everything is working, including the battery gauge. I am looking at installing a 12SI alternator.

I have read about connecting the brown wire from the cab to terminal 1 of the 12SI. Inside the cab that goes through a light bulb to the ignition switch. I have also read some posts that talk about a resistance wire. I don't know what I have, but I know I don't have an idiot light for the alternator. In order to properly use the 12SI, do I need to add an idiot light? What if I don't and just connect the brown wire from the cab? I do have a brown wire with white stripe at the ignition switch, is that a resistor wire? Is the brown and white wire to the ignition switch only present on a truck with a gauge cluster? The wiring diagram shows both brown wire to an idiot light cluster, and brown and white wire to the ignition switch, connected to the same terminal in the cab, but that does not make much sense to me that both could be present because it seems the idiot light would not work.

I have read about connecting terminal 2 of the 12SI directly to the output terminal of the 12SI, and that is how I see most online information about the wiring done. But then 48richard brings to question the point of terminal 2 is to measure voltage at some distance away from the alternator. As far as I can find, that is still a question, and I am wondering about it, too. Is tying the red and blue wires together at the regulator connector, and connecting the blue wire to terminal 2 of the 12SI accomplishing this "measuring the voltage some distance from the alternator," or is it just flat out not needed and putting a very short wire from the main output of the alternator to terminal 2 just fine and dandy?

I don't understand the post above where VetteVet talks about "Now for those of you who have the battery gauge instead of the idiot light then you will have to maintain the wiring in the diagram below. Go ahead and extend the wires and convert the alternator..." Well, I have the gauge and shunt wire and fused wires that lead to the meter in the cab, and I don't plan to alter that wiring, it seems to work fine. What does "Go ahead and extend the wires and convert the alternator" mean? Does this mean if we have a gauge cluster and everything is currently working OK with a externally-regulated alternator, the same jumpers should be installed at the regulator and the same connections made at the 12SI alternator as shown in the idiot light diagram?

Read this thread very carefully and it should answer your questions.

http://67-72chevytrucks.com/vboard/s...d.php?t=417872

[dmjlambert]

Thanks, a lot are answered. There is a surprising many different ways people are doing the upgrade, and I am amazed by that. It sounds like for a 12SI, I just need to jumper the wires at the external regulator connector like is done on trucks with the idiot lights, don't worry about resistance, and if I get engine run on, install a diode on the brown wire. In the jumper at the external regulator connector would be a good place for the diode.

A still unanswered question: "Is the brown and white wire to the ignition switch only present on a truck with a gauge cluster?" To answer that, it would take somebody peeking under the dash at the wires going to the ignition switch, on their truck originally equipped with idiot lights and with factory wiring. Unfortunately, I have a truck with gauges and don't know anybody with a truck equipped with idiot lights.

[VetteVet]

Originally Posted by dmjlambert

Thanks, a lot are answered. There is a surprising many different ways people are doing the upgrade, and I am amazed by that. It sounds like for a 12SI, I just need to jumper the wires at the external regulator connector like is done on trucks with the idiot lights, don't worry about resistance, and if I get engine run on, install a diode on the brown wire. In the jumper at the external regulator connector would be a good place for the diode.

A still unanswered question: "Is the brown and white wire to the ignition switch only present on a truck with a gauge cluster?" To answer that, it would take somebody peeking under the dash at the wires going to the ignition switch, on their truck originally equipped with idiot lights and with factory wiring. Unfortunately, I have a truck with gauges and don't know anybody with a truck equipped with idiot lights.

All you need to do is to extend the brown wire from your regulator plug to the no. 1 terminal on the 12SI, alternator, and extend the red wire from the regulator plug to the no. 2 terminal on the 12SI alternator.
You will have to get an adapter plug for the 12 SI alternator from any of the auto stores. They usually come with short leads which are red and white to splice the regulator wires into.

This is the way I do it and you can keep or eliminate the external regulator and its harness. The brown and re wires are run to the 12 SI and the rest for the harness is left alone. Your battery gauge will work just fine if it's working now.




I have an idiot light dash in my truck so I don't have the two four amp fused wires shown in the diagram above. I can't get into the cab of my truck to check the ignition for the brown/striped resistance wire that you have, because I have it on jacks for the time being. I will check it as soon as I can.

From what I have read the factory put it into all the trucks and car harnesses
with the light dashes, in case the bulb blows, it will provide backup resistance to the alternator to keep it charging.

Here is a diagram of the wiring for the idiot lights with the resistor wire from the key switch.



The only difference is the two brown wires meet inside the cab at the firewall block and only 1 of them goes out to the regulator.