96 Sunfire 2.2 Electrical Problem

DK96SUNFIRE

MEMBER
1996 PONTIAC SUNFIRE
4 CYL
FWD
AUTOMATIC
120,198 MILES

The alternator and battery both got tested and both are fine. The car is somehow NOT keeping it's voltage while running. All the dash lights flash on and gauges stop working while driving and it dies.

The power cable on the side of the alternator is supplying power. The two wires (brown and light green) on the harness of the alternator are not sending any power BUT when I try to test the brown wire the car's idle drops and the lights dim.

The battery wires are clean and tight

What is this wire? Could this be the problem?

On a side note, not sure if this is relevant, but the ABS light was coming on and staying on till shutting of the car and starting it again.

Thanks, Dylan

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9 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

I need you to check the red wire that comes from the starter to the alt. It has a fuseable link built in. Make sure there is 12 volts getting to the alt. Next, I looked up the schematic. There is a brown and a gray (no listing for lt green). Regardless, the brown wire goes to the indicator lamp control, and the gray goes to the alt output control. The pictures are a help. I can't tell for sure, but could one be dark gray and the other light brown?

I have uploaded a copy of the charging system from the battery, alt, to the PCM. Take a look at it and let me know what you think. Based on the fact that you are getting NO power from the alt, leads me to believe the alt is no good (even though it is new). Did they bench test it before selling it to you? If it tested good, check both wires for continunity. If that is good, the alt is good, then the PCM must be causing the problem. Let me know what you find.

Joe

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Friday, November 19th, 2010 AT 5:56 AM

DK96SUNFIRE

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8 POSTS

I pulled the alternator and brought it to NAPA and they benched it. They said it was still good. Another strange factor is that the car will stay running while idling but when I drive it, the car will die.

Just tested the red, reads a constant 13.8-14 volts.

The two wires must be brown and grey then. Neither of them light up the circuit tester. Tester is properly grounded and shows continuity on other circuits.

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Friday, November 19th, 2010 AT 6:06 AM

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

I hate to say it, the next step is the PCM. Before you do that, tell me if the alternator has an internal regulator. From the picture, it doesn't look like it does. That tells me the PCM regulates the voltage. One other question, you said it shows 13.8 to 14 volts. Is that with the engine running?

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Friday, November 19th, 2010 AT 6:10 AM

DK96SUNFIRE

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The alternator has an internal regulator yes. I called the local Chevy dealer to confirm earlier today.

That's with the engine running.

Just tested with it off, 13 volt reading.

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Friday, November 19th, 2010 AT 6:14 AM

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

That sounds correct. The alt is charging the battery. Just for the heck of it, I looked up the alt for your vehicle. The ones I saw have a black shield over the rear of them. I looked 3 different places and all were the same.

Regardless, one last question. Does the battery go dead while driving? Do you have to recharge the battery or jump the vehicle to get it running again?