RobLo

Greetings, I have a problem, did a search and found some posts but will ask here and in the Tech Forums. Coming home from PA. yesterday, air temps in the low 100's and stuck in VERY slow traffic (accident up ahead). I had the A/C (figured it might be better for cooling as the fans stay on), radio and radar detector on, the voltage starts fluctuating wildly, dropping down into the low 11's, driving lights and dash lights doing the same, at one point the Passport powers down on it's own due to "low voltage". Now I'm worried, last thing I want is to get stuck in Staten Island. I get off the Expwy. and start moving again (although slowly), the voltage increases again but never gets above 13. Water temp between 210* and 220* so I figure no drive belt problem (had the belts changed recently), I eventually get past the jams and get moving. Voltage goes up into the high 12's and maxes out at 13.2 when going highway speed. Got home O.K. but worried about that fluctuating episode, any idea's thoughts, suggestions? Thanks to all.....

Gary '09 C6

You were drawing a heavy load on the electrical system in that slow/stopped traffic (low engine speed)...
just could be your battery showing its age. Put a tender on it overnight and then have the battery
load-tested afterwards.

RobLo

Thanks, just went out and started up, no load 13.5-14 volts, full load in Drive 13-13.5 volts, Tender is on now.

unixcorn

At idle, the alternator doesn't put out enough current to satisfy all the electronics. Normally the battery will make up the difference. The battery also serves to stabilize the pulsating DC from the alternator. As the battery ages, it loses its ability to do both well. I am interested in reading how the load test goes.

RobLo

O.K., a followup, I charged the battery overnight and just did a load test. Voltage was 12.94 before startup, dropped to 11.1 during cranking and stabilized around 14 when running. According to a YouTube video on how to do a load test, the crucial numbers are 12.5 before starting and 9.6 during cranking so I was well above that. I also noticed that my voltmeter read a full half volt higher than the DIC so when I thought I was getting 13.2 the other day I was actually (if the voltmeter is correct of course) getting 13.7 volts. I did my DD also, the numbers were 12.6 and 10.8. That being said, I will probably change the battery anyway, it's at least 3 1/2 years old so it's probably time. Thanks again for all the help.....

Gary '09 C6

...and as you likely already know, make sure the new battery is brought-up to a full charge.
They sit on the store's shelves for months sometimes...

not08crmanymore

and how old is your battery?