dv-

'12 TL Base 3.5L, 55k.

So, with the cold weather we had this week, I telecommuted and avoided driving when it was -20+F, but did take a couple trips at -10F that caused the maintenance minder to show a "check charging system" message and illuminate the battery light. Subsequent trips yesterday and today (up to the mid-teens!) caused the "low battery voltage" warning to come up, but that went away on its own today.

On my way home from work today, I hooked up my wifi ODB-II reader and graphed the system voltages. It read a steady 13.8v as long as the car was moving. Stopping/idling dropped it to 13.0-13.2. There was one takeoff from a dead stop that briefly showed 11.4v, but I kinda figured that was a goofed reading or something, because I couldn't duplicate it. My understanding is that the ECU reads voltages 0.2-0.5v lower than what I would read at the terminals with a multimeter, if I could find my darned multimeter. ;-)

I am also hearing an odd whining noise I didn't remember hearing before, it's only really audible <15mph but it pitches up and down w/ rpm. Sounds sorta like a vacuum cleaner running in down the hall or something.

Are these voltages normal?
Could the extreme cold have damaged a pulley or bearing or something? (Causing the noise.)
I am seeing no error/trouble codes to reset, so am wondering how I might reset the Charging System warning to see if it pops up again?
The app I have shows raw data from the sensors, but not which sensor is which. Is there a guide for that somewhere?

Thanks!

dv-

Ran errands this morning. After the third start, the error didn't come back, and the noise went away at some point too.

It's like the darn car is running Windows: Millennium Edition. I think it's telling me to move somewhere warm.

Teddybear

Chances are it's your alternator on it's way out. I'd get your alternator checked. I experienced similar, where i heard high pitched noises on and off for a few months. Then one day my check charging light came on, only mine never went away. The car died later the same day, but thankfully, i had just made it to my mech's parking lot. I think charging voltage at battery should be 14.7V.

thoiboi

Agree with alternator.

dv-

Fiddlesticks.

losiglow

iTrader: (1)

95% chance it's the alternator. Alternators often start acting funny when they're on their way out rather than dying altogether. Regardless of load, idling, etc., you should be seeing a constant 13.7V - 14.2V when viewing from the OBD. The 13-0V - 13.2V and especially the <12V is definitely no bueno.

The whining noise is almost certainly the alternator diode on its way out. It could be a bearing as well but more likely the diode. I had the exact same situation at about 150K miles. Whining/whistling noise from under the hood with voltages dropping to around 12.0V - 12.4V. You can replace just the electronics board on the alternator but it's about the same price as replacing the entire alternator. I just replaced mine with a Duralast from Autozone since they have a lifetime warranty and an alternator only takes about an hour to change. I figured if it dies, I'll just get a new one for free . After 35K miles it's still going strong.

It's from a BMW but there are lots of videos and articles online