DarrellGS4

Ok I have been seeing a drop in voltage while in gear and I would like to have some opinions on it. Most of the time it hovers around low 12's but I have seen it drop as low as 10.7. New battery as of 1.5 months ago. My only thought is voltage regulator may be bad. I had the alternator tested right after the new battery was installed and they said that it was good. For some reason I am getting low voltage with rough idle. I have the Teck Kit on order for better grounding but need some input. Here are a few videos to show exactly what is happening.

http://www.youtube.com/watch?v=FaNCkuAmTEc

http://www.youtube.com/watch?v=iky2HjYiFeI


Sorry the videos are so jumpy

Big Mack

iTrader: (1)

It looks fine. There was no audio, but I'm assuming after seeing (kind of) that you have a stereo in there, I would venture that the battery is giving a quick discharge (bass hitting), and that's causing a dip. As long as it's not long-term, which it does not appear to be, you should be fine. If your voltage never got above 12V with the engine on, you may have issues.

You should be! Get a tripod... (JK...but it did make it hard to read).

Big Mack

DarrellGS4

Thanks...but why does it idle rougher as it drops? Or would that fall under the motor mount? I wouldnt think that bass could cause that...maybe I should get a cap or voltage stabilizer? Would that help??

GSteg

iTrader: (15)

You may be getting rough idle because your ignition system doesn't have enough juice.


Turn off all the accessories in the car and have the car running at idle. Take a volt meter and measure the voltage across the battery. It should be reading ~14.0v-14.5v.

DarrellGS4

Ok, I'll try that tomorrow.

Why does the voltage drop in gear and go back up in park?
Thats odd...
Also it goes up a bit with the AC on.

CK6Speed

iTrader: (1)

The alternator puts out more voltage as RPM's rise. When you are in park, you are idling at a certain RPM. When you put it in gear, your RPM's drop a little. When you turn on the AC, your RPS's rise a little. All varying by a couple hundred RPMs only but varies the voltage your alternator puts out at that lower RPM range. The GS has always had a low idle problem if I recall. If I don't run with my AC on, my idle dips a tad and you feel more engine vibration. Fortunately I live in Hawaii so the AC is on 24/7 even if its 65 degrees outside at night

DarrellGS4

Thanks all...

So my take is that I need to check the voltage on battery tomorrow. If its not 14.0 +,- .5 then I have possibly a bad voltage regulator? But if it is in that range then its time for a Capacitor or Voltage Stabilizer?

DarrellGS4

Real quick...

If it is my ignition system, what would be the fix?

GS FONZy

iTrader: (6)

I didn't see any dramatic drop, that's nothing. If you have an audio system watch it when you hit heavy bass notes, worry about it when it stays that low and does dot go back up.

DarrellGS4

Thats just it, goes low and doesnt come back up until I start driving. Been researching getting a new capacitor...had one but it went out; not sure but I think thats when I started having the drop in voltage. I see that voltage stabilizers are nothing but caps in a box, pretty much new that when they first came out. I think that I may get 2 farads and see if that makes a difference. Opinion?? Would it make a difference with the proximity to the battery for a cap?

GSteg

iTrader: (15)

Well its most likely not the ignition system. If its not getting enough power, its most likely the charging system isn't delivering enough power. The amount of ampere at 600rpm isn't the same at 900rpm. If you've turn off your audio system and everything else, and your voltage at idle is about 14-14.5v, then you're okay.

macd7919

iTrader: (10)

You arent going to get 14-14.5 volts at idle, that is the maximum your car will put out when you rev the engine. While at idle you are most likely going to see 12.2-12.7 volts, anything within a few tenths of that is fine. The only time you really need worry is if the car is consistently under 12 volts while driving.

DarrellGS4

Ok, thanks...
Guess its time for me to listen up to all the hype of bad motor mounts?

GSteg

iTrader: (15)

Mine idles around 14v. Even my sister's 05 Honda Accord idles around there. Unless my meter is broken, most cars i've measured read about 14v. It's the ampere rating that mostly changes with engine revs. If you're getting 12.2-12.7v at idle, then you've got a pretty weak charging system. The battery alone (at least my duralast gold) puts out~ 12.5v without the engine running).

macd7919

iTrader: (10)

I've been Mecp certified since 1997 and was an installer for 6 years. I've seen PLENTY of cars that were in the 12v range at a low idle.

Voltage at idle isn't really what he should be worried about, as long as it is over the voltage of the battery at rest (car off). If you put a multimeter on the car and then just rev up the engine from under the hood while watching the meter and see the voltage rise along with the rpm up to around 13.9 (or above) volts than you are fine.

Btw - V=IR you can't have a change in amperage without a change in voltage at a common resistance. In other words, in order to increase the amperage the alternator is putting out the voltage needs to be raised i.e increasing the rpm of the engine.