Voltage Fluctuation

[Andrew666]

Hi has anyone noticed or experienced voltage fluctuation with their car.

I’m not sure if this is part of their fuel economy approach (decreasing alternator load therefore engine load) and only charging the battery when required. But I have notice on my Scan Gauge (also checked with a multimeter) that voltage fluctuates between 12.5 to 14.3 volts when driving the car above 1500 rpm at normal running temperatures without lights or other electrical accessories on . No warning lights come on or codes are set.

Thoughts?

[cruzinbill]

nope solid 14.1-14.4

[Sbeezy]

You might have a bad alt. other than that the alt's voltage regulator is probably ECU controlled so that might be the issue. but that doesn't explain the voltage fluctuations, I would say turn on the high beams, defroster as this should put a nice load on the alt and see if the voltage stabilizes and report your findings.

[BRZnut]

Originally Posted by Andrew666

Hi has anyone noticed or experienced voltage fluctuation with their car.

I’m not sure if this is part of their fuel economy approach (decreasing alternator load therefore engine load) and only charging the battery when required. But I have notice on my Scan Gauge (also checked with a multimeter) that voltage fluctuates between 12.5 to 14.3 volts when driving the car above 1500 rpm at normal running temperatures without lights or other electrical accessories on . No warning lights come on or codes are set.

Thoughts?

Yes!! I noticed the same thing while on a 10 hr trip to Myrtle Beach. I have a radar detector that gives voltage readings. Around town with the climate control system on or off it always runs 14.2-14.5 volts.

During the trip for some reason I turned the climate control completly off while driving for several hrs at interstate speeds. The voltage dropped to 12.4-13.2. (switching quickly back and forth between those numbers). When I turned the climate system on and it went up to steady 14.2-14.4.

Seemed like with no load on the car and driving for several hrs the regulator reduced the voltage. Maybe to not over charge the battery? Maybe as way to increase MPG???

I was concered at first that maybe the alternator was bad but this happened 4 weeks ago and everything has been fine since.

[cmarks20]

Originally Posted by cruzinbill

nope solid 14.1-14.4

Same here.

[Partial Stall]

The regulator does this from time to time in my car. However the lowest I've ever seen it go (per torque app) is 13.6 volts, and alarmed at 13.5 volts. Most of the time the alt is charging the battery between 14.1 and 14.4 volts with a mean of 14.3.

Keep in mind that most of these fluctuations are normal so an overcharged state doesn't happen in the battery. Overcharging a battery can cause expulsion of gas and bubbles coming out of the battery bay. Not good stuff.