I'm curious what other people are seeing for voltage if you monitor it while driving. My 02 r53 showed voltage that looked low to me, but two alternators both tested functional.

 

headlights, fog lights, charging cell, and usb Bluetooth adapter, I will see 13.8-14.1, that’s pretty much full load. 13.9-14.1 without the load. This is via scanguage, idling and driving. Every once in awhile it will dip down to 12.9 but that’s for a brief second or two but normally goes right back to 13.9-14.1, probably just communication between the scanguage and obd.

 

As Jason mentioned above - I run my parking lights and Rally spot lamps day or night/anytime I drive the car. I have the dealer installed voltage/oil temp combo in my Mini and rarely observe voltage dropping below 13.8 -14 while driving. Even with the fogs and headlights turned on (lots of deer out here). The only time I see a voltage drop to 12 or 13 is when: either the AC, cooling fan kicks on or turning at low speeds (steering pump is activated). Other than that 14.1 volts while running.

 

that is what i would expect from a normally functioning automobile. my 06 is not holding voltage that well and i can't help if a couple of my intermittent quirks could be attributed to fluctuations in voltage. i guess i'll dig out my spare alternator and swap it in.

thanks for the validation, y'all.

 

Mine runs around 13.6V, which sounds lower than it should but I just replaced the battery which lasted 9 years telling me my charging system is fine.
As others have mentioned, voltage dips are normal, especially when the PS pump is doing work.

 

Don't forget your ground strap ( frame to motor mount). Mine had corrosion underneath the shielding. Just swap it with a new 2 or 4 gauge wire and some copper ends (super cheap DIY). The stock piece is over $50. I did mine and all the voltage/charging issues were resolved (this is after swapping alternators a few times).

 

I use a scangage II to monitor my voltage, average mpg, speed and water temp. The voltage is 14.1V most of the time unless I am idling with lots of accessories on. The scangauge II gets data from the DLC port (i.e. the ECU) under the dash. For reference, this is on a 2003 MCS

 

In case anyone is curious, I changed my alternator a week ago or so. The voltage readings are definitely better now. When I'm running my ac now, I'll see dips that I think probably correlate to the compressor cycling. However, sometimes the voltage takes a little longer to recover than I'd prefer. Regardless, out with the old and in with the new.

Also, the old was a Bosch rebuild. No idea on the age, though