Car idles at 12.1 volts

[My63bug]

So my car will only idle at around 12 volts. I can get it up to 13 .3 if I'm at 3000 RPMs. It's an old school bug. I installed everything new. 95 amp alternator. Two 800 CCA group 78 batteries. 1/0 welding cable. Running about 1500 watts total. I have no dimming issues. The car won't dip any lower than 12 volts no matter how hard or long I play the stereo even with headlights on... any thoughts?

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[LosIsATool 5,000+ posts]

12v won't keep a 12v battery charged. That will be a problem.

Check the grounds or you might have to get a voltage regulator.

 

[My63bug]

It's ground very well. I went a little Overkill

 

[LosIsATool 5,000+ posts]

Yeah then you will need an aftermarket all with a regulator. That battery won't last long. Might want to put it on a charger every night

 

[My63bug]

It is an after-market alternator. All alternators for old school bugs are aftermarket. They come stock with generators LOL. It has an internal regulator. And I am running two batteries

 

[Mayhem]

Is it super hot where you are?

During the summer my idle is 12.9-13.5 depending how hard I've been playing the system.

I have a stock alt but I also have over 350 AH worth of reserve.

Even with heat, I think you need more alt or more out of that alt. Eternal regulate it, but heavily monitor it. Easily can kill an alt if you're not careful with it.

There are a few of HO Alts that are made for bugs.

 

[My63bug]

Yeah gets hot. But it's been doing this ever since I put the system in. About a year. It's not a daily driver... iv got like 210 ah.. like I said the weird thing is. I can crank the system and run it for an hour straight and my voltage won't dip below 12 as long as the car is running of course

 

[adulbrich 5,000+ posts]

Yeah gets hot. But it's been doing this ever since I put the system in. About a year. It's not a daily driver... iv got like 210 ah.. like I said the weird thing is. I can crank the system and run it for an hour straight and my voltage won't dip below 12 as long as the car is running of course

Since everything is aftermarket, there can be one of two problems.

1. The alternator's regulator is bad. Pull it off and take it to your local alternator shop. They will bench test it for free.

2. Have your batteries individually load tested, not wired to each other or anything else. A bad battery can pull the system voltage down.

12.1v is less than normal fully charged float voltage. Your battery is not being charged, possibly maintained at best.

If you have your alternator and batteries tested like I have suggested, you will figure out your problem.

/thread

 

[wew lad 5,000+ posts]

what's the voltage at the positive post referencing the alternator case as ground.

i.e. positive probe on post out the back, negative probe on the case. internal regulation MIGHT be an issue.

otherwise its a bad voltage regulator or battery with a short, but i doubt its the battery

 

[adulbrich 5,000+ posts]

what's the voltage at the positive post referencing the alternator case as ground.
i.e. positive probe on post out the back, negative probe on the case. internal regulation MIGHT be an issue.

otherwise its a bad voltage regulator or battery with a short, but i doubt its the battery

I doubt it's the battery too, but customers at the shop had some weird issues when their battery was on its last legs. I don't think the battery has an internal short, but weirder things have happened.

I strongly believe it's an alternator issue. If not internally, then with a wire leading into it.

 

[Sierra Nate]

Are you measuring voltage by the dash board volt meter or with a vOhm meter connect to the battery posts?

 

[Boomin_tahoe 5,000+ posts]

@My63bug have you noticed if your instrument lights, if you have any, started fluctuating weirdly/dimming? My s10 did this and turns out something in the alt started failing. Not sure what the exact problem was but after replacing alt, fixed the issue. Just a thought for ya.