I am trying to figure this problem out.. Recently I could not get my "GEN" light to work and after re-wiring the light going from the bulb (- side) back to the alternator I still can't get the light to work.

Before starting my test I confirmed that the "L" wire coming from the back of the alternator was grounded. Now when I test it, there is NO GROUND! There are three wires coming out of the plug. The red one goes back to the charging post, the brown does not get hooked up and the black was the "L" wire. Is there any reason that either of these two wires which were formerly grounded (when engine not running) are no longer grounding???

I am trying to figure this problem out.. Recently I could not get my "GEN" light to work and after re-wiring the light going from the bulb (- side) back to the alternator I still can't get the light to work.


Is this the only symptom you are experiencing? I imagine once the car is running, if it starts, the lights are dim since the L terminal is responsible for activating the vlotage regulator in the ALT.

Try this...with the ignition off, do you have continuity through the GEN light socket? If not check the bulb and/or wires. Once that is good verify the wire is going to the L terminal on the back of the ALT.

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Well worth the $$$. I am currently installing MAD Electrical's New System package and the instructions and attention to detail is just incredible.

Appreciate the feedback from everyone.. I have figured out all of the wiring. The only thing that can be wrong with my system at this time is that I fried the internal regulator in my CS leading up to this point.

Per the Mad Elec. instructions, I have the factory resistance wire deleted/removed. I have all other connections capped off except the two wires necessary. I am simply not getting a ground at the alternator plug from the "L" wire like I am supposed to. I have several other Chevy vehicles (Late model CS equipped) on the lot and will go and test them to see if they have ground at the "L" wire when the engine is not running. If I find that other alt's have that wire grounded I will then know that my alt is just bad, and because it is my fault for messing it up... Lesson learned.

I guess my advise would be for people trying to figure this out would be to purchase the Mad kit BEFORE they make the same mistakes that I have made leading up to this point..

Will post back to let everyone know what I find with my checks.

The L wire should not be grounded. 12volts is fed from the light to the alternator to energize the field. So I don't understand what you mean by not getting ground on the L wire. The only time you would is if the charging system fails and the regulator grounds the L wire to illuminate the light.

I have the opposite problem. My Gen light turns on when I turn the key on and stays on while the engine is running. Any suggestions?

Also, under my dash is a connector that has green and pink wires. Were does it connect to? I cant find it on the wiring diagram.

John
Montana

Dnult-the "L" wire coming from the alternator IS grounded when the engine is not running. When you turn the key to the "Run" position, 12+ is applied to one side of the "GEN" light and it lights BECAUSE the wire coming from the alternator to the other side of the light is grounded UNTIL you start the motor. After you start the engine, the field energizes and then the "L" wire is no longer grounded and the "GEN" light goes out. If the alternator/regualtor fails, then the field de-energizes and grounds again and lights the light

So yes, the "L" wire is supposed to be grounded when the engine is not running.


68 Convert-tell me more about your set-up. Is it one wire? 10/12 SI, or CS series? How do you have it wired? How long have you had the problem with the light lighting up? I can assist you but I need to know more specifics about your set-up in order to guide you.

I put a new wiring harness from M&H wiring about 4 years ago. I had it made for a 12si model. I just put a new engine in my car and put a GM serpentine system on the engine. It comes with the CS130. I send my wiring harness back to M&H to modify it for the 130. The four pin connector they put on only has 1 wire coming out of it and it is brown. I am not sure what pin it is coming of of, but I can look later today. I just got the car going again,so it is a new issue. Thanks for the help. If you need any more info, let me know.

John
Montana

John, take a voltmeter and test that brown wire as it comes out of the plug (with the plug plugged into the alternator & all other wiring attached as per normal operation) and see if it is grounded when the engine is not running.

Do you know if you still have a 24 gauge Brown with White Stripe resistance wire teed off of the 16 gauge brown wire as it comes out of the fuse panel on it's way to the "GEN" light? If you do, you need to cut that wire and tape it up as it will give an incorrect reading to the alternator.

Have you checked with a voltmeter at the charging terminal on the back of the alternator to verify whether or not the alternator is charging? How many volts do you see at the charging terminal with the engine running?

Dnult-the "L" wire coming from the alternator IS grounded when the engine is not running. .

We're saying the same thing. When I said it should not be grounded I meant ground should not be manually applied to the L wire. It was my misunderstanding. I completely agree with your description of the L wire as controlled by the regulator.

Thaks to Go69 I have my alternator problem resolved. I just cut the wire and it works like a charm.

Thanks again, now the fuel gauge problem(see post)
John
Montana