Voltage Regulator in cold weather

[David Spektor]

I am re-posting this question as original post did not get any feedback.

On my MY02 WRX when starting in real cold weather (10 - 20 deg F) voltage
gauge jumps to 16.7 V and holds at 16 V level even with headlights,
defroster and fan on high for several minutes - until engine warms up. After
that it gradually drops to "normal" : 13.8 V while driving and around 12 V
while idling on a traffic light.

Did anybody had similar experience? I am not happy to see car electronics
experiencing 16+ V even for couple minutes, but to demonstrate this to the
dealer I would need a really cold weather and car spending night in
dealership.

 

[Tony Hwang]

Hi,
That is normal. In that cold temp, your battery is very weak.
So it'll charge in full rate for a while until the battery
regains it's full capacity as well as car warms up.
Higher current demands higher voltage.
(basic Ohm's law)
Tony

 

[CompUser]

I am re-posting this question as original post did not get any feedback.

On my MY02 WRX when starting in real cold weather (10 - 20 deg F) voltage
gauge jumps to 16.7 V and holds at 16 V level even with headlights,
defroster and fan on high for several minutes - until engine warms up. After
that it gradually drops to "normal" : 13.8 V while driving and around 12 V
while idling on a traffic light.

I'm not a mechanic, but I'd guess your system is
doing what it's supposed to be doing. Batteries
tend to lose their charge easier in colder
weather, and have to work harder to crank a cold
engine. Sounds like the system is detecting your
batt is further "down" and making up for it with
the higher initial charging voltage, then backing
down as the battery comes up.

Steve

 

[The Masked Marvel]

That is typical, lead acid batteries require higher charging voltages when
they are very cold vs. very hot.
Auto electronics is built to run at nominally 14V but must withstand a fair
range to either side of that plus possible transients (load dumps)
*significantly* higher that 14V (say even 50 V or more for 10-100
milliseconds). I would not worry, the car electronics should be designed to
operate at these conditions indefinitely, though you (or the dealer) could
double check the accuracy of the gauge w/ a good, *calibrated* digital
voltmeter just after a cold start.

The drop to 12V at idle occurs because the alternator does not quite keep up
w/ the load at idle speed, again not unusual.

 

[Rick Courtright]

defroster and fan on high for several minutes - until engine warms up. After
that it gradually drops to "normal" : 13.8 V while driving and around 12 V

Sounds normal. As others have said, your battery takes quite a hit when
it's cold, so takes a bit more voltage to recharge cold than in warmer
months. As to the actual voltage, is that measured with a meter or just
off the gauge in the dash? I wouldn't trust the dash gauge for
absolutes, just to let you know things are in a "normal" range. For
example, when mine says 12 v, a meter says 14; when the gauge says what
I'd guess to be about 14 v, meter says 14.5, etc.

Good luck!

Rick