2008 Pontiac Torrent Battery Voltage Issues

New here. Was told by a friend that this is a very helpful community - thought I would try. Hoping someone can help me or the two different mechanics I have brought my car to with this issue.

Here are the details…

In Oct my battery died of natural causes. I know this because I received some fair warning such as dimming lights etc. I got a new one.
It was good for about two months when my car wouldn’t start. It was a cold Minnesota morning but it was in the garage and a two month old batter and our household’s other cars started just fine outside. Took it back to Mechanic #1 and he said he received a few other “bad” batteries and exchanged it.

Two weeks after that - it would not start again! Brought it back to mechanic #1 and he did all the “tests” in front of me that showed it should be just fine. He kept it over night and of course it started up just fine for him the next morning. He said just keep an eye on the voltage ( my car has a display for that) and that it should be reading around 14.5.

For the next few days it read fine. Then it began to fluctuate between that and 15.3. Knowing that is to high, I went back in and he installed a new alternator.

The first day, it was perfect, but then it started to fluctuate again back up to to 15.3.

Yesterday I took it to mechanic #2, an auto and electrical specialist, who determined that mechanic #1 did not properly attach/seal the master wire and that was the issue. Cool. I go and pick it up and all the way home (20 mins), the voltage stayed around 15.1. I call mechanic #2 and they “huh, we drove it and it seemed fine. Can you bring it back tomorrow for 15 mins and we will hook it up again and check some things out”.

I will do that but at a loss of what other avenues if they cant figure this out nor do I want to keep racking up the bills for this.

Any insights would be most appreciated! Thank you!

The Engine Control Module regulates the voltage in your vehicle. There may be a problem with the ECM.


It could be a loose or corroded ground connection.
The voltage regulator circuit (wherever it is) depends on a ground connection to make reference to.

The 15.3 volts is a little higher than it should be but it isn’t real bad. Have the shop check for any AC voltage while the engine is running around 1,500 RPM. That shouldn’t be more than 0.1 volt. The higher voltage could be happening due to a bad connection on the battery sense wire which would make the regulator think the battery charge is lower than it really is. Cleaning all the connections including the grounds is a good thing to do.