3G Alternator concerns-PLEASE HELP!

I've had a 160A alternator for the past 2 years with no issues. I'm running a 4G power wire and had 13+ volts at idle. Out of the blue, I go to work this morning and immediately notice my head/dash lights are a little dimmer than usual. Even with increased RPM the factory gauge reads around 10-12. I know the factory gauge sucks, but even before this morning the factory gauge would read right between the 8 and 18, either at idle or with more RPMs. I hooked a voltmeter right to the battery and key off/ignition off I get 11.8 volts. With the engine running with either all accessories on OR off (AC at max) I only see 12.1 volts at the battery, even with increased RPM. It was pouring today so the guys at the auto parts store wouldn't test it in the rain. I have absolutely no starting issues, and I drive 40-45 miles each way to work. Any ideas?

HISSIN50 said:

I might check power output at the alternator itself (at idle and/or 2K RPM).

I'd also check the sense wire on the regulator.

Make sure your circuit protection didnt pop.

Good luck.

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Do you mean check the volts at the power wire coming off the alternator? I did and it also reads the same as at the battery. If I'm completely off, please tell me how to do it correctly. Lastly, what is the circuit protection?
Thanks.