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On my 95 B6, the idle bucks at a stop light when the a/c is on. When, I drop the car into neutral, it stops bucking and idle picks up. Since our automatic transmissions are electronic, could a weak alternator be the culprit? I've tried doing some research on the forums but everything that I have tried does not seem to help.

Open to all suggestions (except swapping the car to a manual )

Thanks,
Keith

Possible. Checking for a weak alternator is easy. Drive at night with your lights on and use your turn signal and see if the lights fade/illuminate with the signal. If so chances could be its a little weaker than new but still working obviously.

Hope that can help you.

Check the battery and alternator, disconnect the negative cable with the car running, if it dies then the alternator is what is keeping the car alive, replace the battery. Buy a cheap voltmeter, with the car running in P you should be seeing about 14.2 volts at idle, also if there is any corrosion on the battery posts clean it off and then wash then with water and baking soda mix with a small wire brush to get it all nice and clean.