Okay I've noticed over the past few weeks that my volt gauge is sometimes very low.

I also noticed when I'm in park I have a searching idle, it goes up and down by about 150 RPMs, and when it goes down the volt gauge goes up. When the RPMs go back up the volt gauge goes back down.

On top of all that, I noticed that sometimes my blinker won't blink, then is when the volt gauge is down, sometimes into the red.

Today I stuck a Digital Volt Meter on the battery, and watched the voltage. With the car off it is at 12.68, with the car idleing it fluctuates with the idle, when the idle drops, it reads about 14.3-14.5, then the idle recovers, the volts go down to 12.8-13.2.

I then went one step further, I disconnected the battery while the car was idleing, battery still was reading 12.68, the volts at the cables was a steady 14.1, and my idle no longer surged up and down, it stayed steady. This made me question my battery.

I checked voltage at the alternator in all cases, it was the same as at the battery. I checked using the frame and alternator case as ground, and once again everything was the same as before. This proves to me that I do not have a bad ground, or connection from the hot side of the battery to the alternator.

The question still remains, is my battery bad, or is my alternator bad... or is there something else going on. I personally think it's the regulator in the alternator. Anyone else have any ideas?

Sorry it's a long post. I just need some input. I posted this over in electronics, but got no response... maybe it will work better here?

 

Sounds like a similar problem I've been having. My alternator won't sustain a load properly... with the headlights on, my output voltage drops by a full volt. Have you tried checking the voltage with some accessories powered up?

I dropped in a new battery last year, since I needed one. I also just rebuild my alternator (new brushes), and I checked the rectifier and stator per GM's alternator service manual. Everything checked out, except for the regulator. I couldn't check it, because I didn't have the proper testing equipment.

That's interesting that the problem went away once you disconnected the battery. Maybe try a spare, if you have one.

I wonder, if the regulator isn't regulating properly, the decrease in power to the ignition coil causes the idling variations. For example, if the regulator can't match the proper voltage, and it's bouncing between two places, it's affecting the power supply of the entire car. The ignition coil is receiving less power, so it's outputting a less powerful spark to each plug. I'm not sure if that would cause RPM fluctuations, or if it's even mechanically possible. Just something I thought of.

My next step will be a new regulator.

 

Check your connections first, if you haven't already. If they are good, take the alt to a parts store than can test your alternator.

 

Parts store said alternator is good, watched them test it, the machine said pass on everything. They then told me to bring my car back and let them check the battery and charging system. They checked it, said it is charging okay, but the battery is low. I don't understand this, as I drive it every day, more than an hour a day most days. Why would the battery be low?

I charged it over night with a charger, the charger slowly dropped to 0 amp input, which I assume means the battery took the charge, as all other batteries I charge do that when they are fully charged.

Anyways I drove around on it today, the gauge started way up, above 13 when running, but slowly it dropped back off (by slowly I mean over hours) I went to the gas station, gauge stayed above 13, came home... few hours later went to school, gauge was then a little below 13, came out of class, went to my girlfriends, battery gauge was now getting closer to the red, but not touching the red yet. On my drive home the gauge sat at the red the whole way. I know it's not completely accurate, but it does give me a pretty good idea of where my volts are.

I have yet to check all my connections, I did make sure the cables are on the battery and clean. I checked the ground, both by resistance and voltage difference, all looked fine.

I need a little help with wiring... there's the black thick gauge wire, goes to the Starter terminal correct? The hot side of the battery goes to the Starter Terminal also correct? Then there's a brown wire that comes off the ignition?

Basically if someone could tell me what all the wires do and where they go I would be happy... my Chiltons manual has diagrams but I can't really read them too well.

I'm not so much worried about the idle, as I have been told that it will vary slightly as the alt kicks in and out.

Battery just doesn't seem like it should be bad, the date on it proves it is less than a year old, and it's no cheapie (Die-Hard Gold).

Any other ideas?