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The electrical gremlins are at it again! The voltage on my 2005 is fluctuating from 12.2 at the lowest to 14.4 on my digital display with engine running.
Tail lights dim slightly in and out as well as interior lights on rear view mirror. Brand new AC Delco alternator. Optima battery tested good. Cleaned grounds under battery. Any advice on what to check next? I’m assuming a short somewhere or other ground to check? I have limited skills with a voltmeter and can’t really afford to send her off to a shop at the moment. Also cleaned up BCM as best as I could and made sure everything’s tight there. Any advice is greatly appreciated!
If you have a DVOM and have limited skills I would do a voltage drop on the positive and negative sides of the charging system…with the car running at 2500 RPM put some electrical loads on the car….blower, high beams, defroster and take one lead of your DVOM and place it on battery positive…other lead place on the alternator B+…voltage drop should not be more than 0.5 volts…to check negative side place one lead of DVOM on battery negative and the other lead on the alternator case…again should not be more than 0.5 volts….dim or flickering lights are normally a ground issue…below is the wiring for the tail lights and interior lights….can also be bad bulb connector…you can also check alternator output voltage between alternator B+ and the alternator case…when the car is running the lowest voltage potential is at the alternator case and not at the battery negative terminal…just because your new alternator is new doesn’t mean it’s good…voltage drop shown on my car…0.18 on positive side and 0.10 on negative side.
A common problem on the C6 is the connection point of the battery & alternator cables on the starter solenoid post. Often heat will cause this post to break or the connection becomes loose. Check the cables and if loose remove the nut and clean the cables and reconnect and be easy on the torque so you don't accidentally break the post. If broken you will need to replace the solenoid which would require you to drop the starter.
2005 voltage fluctuating issue
