I've got a 1965 VC that the charge idiot light won't come on. I can ground the wire from the alternator and it lights up and if I take a test light from power to the alternator terminal it will light the test light also. It just won't work when all hooked up. Any ideas? Thanks,Hal

 

Try a different regulator.

- Eric

 

A more fundamental question: Is this a stock external regulator alternator or did you convert to a silly one-wire alternator? Second, what do you mean it won't come on? The proper test is if the key is on with the engine not running, it should be lit. If not, ground the brown wire at the regulator. If the light comes on, the problem is the regulator. If not, the problem is the brown wire or the bulb or bulb socket or +12V source on the other side of the bulb.

 

It's not a stock alternator/regulator. It's a 3 wire 04 GTO unit, large wire to batt, small wire to non switched 12 volts at battery, and brown sense wire to a light or 470 ohm resistor.
With the alternator's brown sense wire jumpered to a 12 volt light the light will light up. Taking the brown sense wire from the idiot light to ground, disconnected from the alternator will light up the idiot light. But when the alternator is hooked up to the brown sense wire I get no idiot light. Makes no sense to me.....
I'm wondering if the PO could have monkeyed with the under dash wiring but can't imagine how or what he could have done to have it work this way.

 

Check for a good clean connection at the brown wire to generator. Is this a new problem or has it not worked since you've owned the car? Also, to use the terminology in the 04 GTO service manual, the 12V unswitched white wire is the sensing wire and the brown wire is the lamp wire.

 

It sounds like a bad alternator or regulator in the alternator. That is a Japaneese alt isn't it?

 

Its a brand new alternator and it is a Mitsubishi. I had it checked before buying it and it checked out good. It may be that the parallel light/resistor in the dash idiot light circuit won't work with this alternator. I'm going to shunt out the resistor and see if that works. Grasping at straws now.....

 

I'm not aware of any resistor in the GEN light circuit for a 65. The internal resistance of the lamp itself is normally used to energize the regulator. If there is a resistor in parallel with the lamp, that may be the problem. Normally there's simply key-switched +12V on one side of the lamp and the other side connects to the brown wire that goes to the regulator.

The other thing to check is resistance drop in the wire between the alt and the lamp. If the resistance is excessive, the lamp may not light even if it is connected properly.

 

are you sure this not a computer control alt. being from 04 gto

 

You HAD to go and make me do it.

Here's a diagram of the indicator lights on a '65 A-body:



As can be seen, the ALT light has power to one side from the IGN circuit through the "IP Lights" fuse, and the other side goes to the ACC circuit through a 10Ω resistance wire, and to the "L" terminal of the regulator.

There is no resistor of any kind.

I know nothing about '04 GTO alternators, but if they are computer controlled (as is the alternator on my '00 Grand Cherokee), then, obviously, they won't work exactly right without the computer.

- Eric

 

The 2004 GTO alternator was kind of an odd ball, it wasn't PCM controlled. It was a one year only alt. As for the resistor, my 1965 Chassis Service Manual shows it on 13-12 and I can see it on the pc board. I just need to see if I can shunt it and check if that works.
I don't know how to attach a picture but I tried to scan the page and attach it to this post. Hope it works.

 

The resistor is the 10Ω resistance of the resistor wire that connects the ACC terminal of the ignition switch to the wire from the panel lamp (the pink wire in the diagram) at the Engine and Dash Connector plug, and to the "L" terminal of the regulator on the other side of that plug.

I'm afraid I was just looking at the panel diagram for a resistor, and didn't look at the whole picture - I though you were looking at a resistor soldered to the instrument panel, and not a schematic that showed a resistor.

So, yes, there is resistance in the circuit between the ACC terminal and the "L" terminal, and, in an original configuration, if someone replaced that resistance wire with regular wire, or just cut it, you could have all sorts of problems.
In a non-original configuration, you could have problems if you left it connected.

- Eric

 

It is an actual resistor, not the resistance of the wire. It is factory connected to the IP, on the pc board, with two #6 or #8 screws just below the light near the bottom of the panel. There's one on Ebay now that clearly shows it. I may have to remove the panel to get a better look at what has been done to it.

 

Is this the one you mean?



I believe that is a ballast resistor associated with the fuel gauge (though I will admit that I may be mistaken, as I am not personally familiar with the '65s).

- Eric

 

The way I read that diagram, the lamp is only connected to power with the key in the IGN (ie, RUN) position and the resistor wire is only connected in the ACC position. In any case, you don't want to shunt the resistor, you want to open the connection to it so all the current flows through the lamp.

 

In the ignition ON position, current flows from the battery, through both the ACC and the IGN terminals of the ignition switch, through both the resistor wire and the ALT bulb IN PARALLEL, into the regulator "L" ("Light") terminal, where it is connected to the "F" ("Field") terminal, and from there to the field coil, and through that to ground. The current flowing through both the ALT light and the resistance wire is enough to tickle the field coil and start the alternator making current when the engine starts turning.

Once the alternator is making enough voltage, the voltage from the alternator "R" terminal to the regulator "2" terminal, and to the field relay winding inside the regulator, becomes high enough to pull the relay contacts closed, connecting the regulator side of the ALT light to battery voltage, and making the light go out.

I have no idea how the light is wired in your car, but there are a whole lot of ways it could be wired (including the original way) that would prevent the ALT light from lighting with an internally regulated alternator.

- Eric

 

In the picture it looks like the resistor comes directly from the alternator light (far upper right light) and is parallel with it as is the drawing I posted. But then again, maybe it is the resistor in the fuel gauge, hard to tell. You might be right in that I should remove the resistor and let all current flow through the light rather than shunt it. This working under the dash is not my favorite past time for sure. It was a lot easier 30 years ago.......

 

I tried to find some info on the reg in your alt, but so far I haven't been able to find much. So far it looks like the hookup you have should work, but as you suspect there may be too much resistance in that line. As a quick test, I would use the test light in place of the dash lite wire to see if it charges and the test lite goes out when the car is running. Unlike the 10SI this alt may require constant power to the lite terminal on the reg remain charging. The 10 SI will continue to charge once it is activated with the lite wire even if the power to that terminal on the reg goes open.

 

It may look that way, but it's not.

Here is a picture of the back of the cluster, with all of the sockets and connections labeled.



You can see that the resistor in question is across the terminals of the fuel gauge.

- Eric

 

Looks like I'll have to isolate the wire from the cluster connector and run it straight to the alternator. Maybe someone has tapped into that wire for something and it's changing the resistance. After all it's a 48 year old vehicle.
I really appreciate all the help guys, you've been a big help. Hal

 

The resistance wire doesn't go to the cluster.
It goes from the ACC terminal of the ignition switch to the firewall plug.

- Eric

 

I just checked the wiring for a 1980s GM with the 12SI alternator and the 10 ohm resistance wire is still there. There should be no need to remove it. Is the Mitsu alternator new or used? Are you sure it's putting out adequate current? Are you sure all the connections are low resistance? Have you considered ditching the Mitsu and getting a Delco 12SI or CS130? I've never had a problem converting using one of those, including my 62 that originally had a generator.

 

OK, let's see if I completely understand. With the key on and engine not running, you ground the brown wire from the lamp and the lamp lights. This obviously says everything from the dash through to the brown wire is working correctly. Now, with the brown wire hooked back up to the alternator and the key on (engine not running), the GEN light does not light up?

If so, check resistance to ground from that pin on the alternator (again, not running). Use a high impedance ohmmeter. I bet the problem is the regulator not providing a low enough resistance path to ground.

 

Oh, one more thing to look at. I don't know about the Mitsu alternators, but the CS130s are notorious for having a bad internal ground path due to galvanic corrosion between the aluminum case and steel stator core. There's even a TSB out that suggests running an external ground strap from the rear frame of the alternator to the block. Try that.

 

Key on,engine not running, idiot light is off. Test light from 12 volts to brown alternator terminal with plug disconnected lights the test light. It's a new alternator and we spun it before I took it out of the store.
I'm guessing I'd have to remove the resistance wire at the ignition switch then to get rid of the extra impedance and see if that makes the light function. Then run it and see what the voltage looks like.

 

Your mitsubishi alt has a L&S (light & sense) connection. This is the same connection as the 10SI. The difference is the 10SI is trio activated and the GTO Mitsubishi is stator activated. This is similar to the CS130. Too much resistance and the lite will not lite as you are experencing. As a test before cutting your resister wire, connect the S wire as you have it (constant power) and use your test lite (power thru the test lite to the alt terminal) where the brown wire was. This will lite the test lite and when the car is started the test lite should go out and the alt should be charging. If this works then it should work on the car with the resister wire removed. You may have a dimmer than usual lite on the dash charge indicator with key on, but It should still work. The dimmer lite will be because of the type of regulator in the Mit alt.

 

Hal, just curious, when do you sleep? Your posts are all hours of the day and nite.

 

Thanks Stellar, the light does light with the test light but I haven't started it again as I have the PS line off it at the moment, (waiting for a 18 mm 1.5 tap but that's another story). I'll try and ID the resistor wire from the starter switch tomorrow and pull it loose. I agree with your assessment about the excess resistance causing the problem. We'll see....
As far as sleep, I'm retired so my hours can be very flexible. That being said, I used to live on 4 hours sleep for many, many years. It seems I always had some sort of project going and I didn't know when to quit. I guess things really haven't changed-my wife just now dragged me in from the shop even though it's only a little after midnight ,LOL.
Thanks again for the help, Hal

 

Success I think. I clipped the resistor wire at the ignition switch and the light comes on albeit at a fairly low intensity just as Stellar surmised would happen. Still haven't been able to run it so it'll be a couple days before I know if all is well with the charging end. Looks good folks, thanks again. Hal

 

It's official, 14.5 volts, charge light out when running. Thanks for all the help people, it was a challenge. Hal

 

You're welcome.

It's just one of those things - if you change one part to something modern and completely different, you've got to reëngineer the rest of the system from the bottom up.

- Eric

 

Thanks for posting the results. This was a bit trickier than most. There is not much info around for the alt you are using. I think it was a 1 year only alt, but I suspect it is interchangeable with a few delco units if the plug is changed. I would guess this no lite issue will come up again when alts are switched even using CS130 and Cs130D alts. It has a lot to do with the type of reg in any given alt.

 

You're right about it being a one year alternator although I imagine as you said it's basically the same as others, information is real sketchy. I'm not very PC and I have to be careful of how I come across with my replies- sometimes they don't come out as I mean them to.
I am a little surprised there haven't been others with the same issue though but then I guess a real purist wouldn't be doing a swap in the car. I want the car to look period but run and drive like a modern vehicle with dependability. Hope it works out.
Thanks again, Hal