Voltage Issues, Bad Alt?

[timma100 10+ year member]

Alright so this is going to sound strange but here is whats going on.. I have 3 batteries total (including the one under the hood) in parallel. The two in the trunk are DataSafe (BC2K look alikes) so nothing to big. Here is my issue, sometimes when I start my car, voltage goes to 14.5V which is normal, but other times, i'll start the car and voltage will stop climbing at 13.5 sometimes even 12.8,. and it will fluctuate around that mark the entire time the car is on regardless of the amplifier status. If I shut the car off and let it sit, then restart, it feels like the luck of the draw. sometimes I get 14V sometimes 13. and sometimes 12... Its in a 1995 Buick LeSabre with a stock 90A alt.. Any ideas?? Thanks

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[DaveVT 10+ year member]

Maybe a faulty regulator

 

[rebelfromva 10+ year member]

Sounds like mine. Tested it earlier and was sitting right at 13.0 at idel

 

[timma100 10+ year member]

Maybe a faulty regulator

Is there a way to bypass the regulator and make the alt run at 100% all the time?

 

[lionfamlee Premium Member]

What RPM is your car idling at? Does the voltage change when you have the alt close to full tilt?

 

[DaveVT 10+ year member]

Is there a way to bypass the regulator and make the alt run at 100% all the time?

That would be a very bad idea. It would charge your batteries at a much higher voltage than they were designed and more than likely cause a very nasty failure.

 

[Fi_ 10+ year member]

Also depends if it's cold out and now warm I know the last few days have been REALLY warm and I've lost about 1v due to weather. also dropping below 13v and fluctuating could be a lot of things I'm guessing a loose belt or bad alternator. Does it squeak a lot when you start the car? does the alternator whine at all? have you looked at your belt to see if it needs tightening?

Could be a TON of things. Did you do big III? maybe a bad ground?

 

[timma100 10+ year member]

I just spend about $750 getting the water pump and AC pulley replaced on this car. The belt is brand new and doesn't squeak, if it is an alternator problem I cant fix I guess I will just deal with it... Not looking to poor more money into this thing //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif Also, I cant really do Big 3 because the alt + to battery is a tiny tiny tab on the alternator :| but all batteries are in full parallel with each-other

But yeah when I first start the car voltage is at 12.1 - 12.5, then it slowly rises to 13 and maybe 14. Then drifts back down to mid 13V

 

[timma100 10+ year member]

So it was cold this morning, the entire drive to work I was at 12.2 volts //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif wtf

 

[dbeez 5,000+ posts]

I say bad ground or a bad battery in the line somewhere.

 

[timma100 10+ year member]

I say bad ground or a bad battery in the line somewhere.

The two in the back sat at 13V the one up front (some poo wally bat) sat at 12.4.. The batteries are frame grounded up front and in back while being in full parallel with each-other.. I'll check my bolts tonight :|

 

[dbeez 5,000+ posts]

A battery can read 13+ volts and still be a bad battery have no amperage out and when sitting it will.pull from everything else in the system every battery needs load tested individually and make sure all Batts are the same battery type example agm or gel cell.

 

[sexy 10+ year member]

A battery can read 13+ volts and still be a bad battery have no amperage out and whispered sitting it will.pull from everything else in the system every battery needs load tested individually and make sure all Batts are the same battery type example agm or gel cell.

Thank you for posting on this.

I have said the same thing to people on this forum so many times that it seams like a waste of time.

 

[timma100 10+ year member]

A battery can read 13+ volts and still be a bad battery have no amperage out and whispered sitting it will.pull from everything else in the system every battery needs load tested individually and make sure all Batts are the same battery type example agm or gel cell.

The batteries are miss matched, the front battery is flooded and the back two are AGM

 

[dbeez 5,000+ posts]

Your battery bank is as strong as your weakest battery and the wetcell will pull the agm batteries down.