Car voltage keeps jumping up and down until car stalls

[ghart999 10+ year member]

For the past 2 days my car is having a hard time maintaining voltage when driving in stop/go traffic or even at idle. I have a voltmeter gauge up front and voltage will go from 13.8 into the 11s or high 10s and back up. After a few times the car will stall out whether driving or idle.

I have a 160A alt and an optima red top. I was convinced the alt was dying so I switched to my stock unit and the same thing is happening. Hence I am sure the alt is not the cause. I have done the big 3 with 0 gauge wire. So no problems there.

Also this problem happens even with the stereo turned off, so no problem with too much amp draw.

Could my batt be dead? I don't have a problem with the car starting so I would think the batt is fine.

No external volt regulator. That is internal to the alt.

Any thoughts as this is making driving impossible as I stall every minute while driving.

Thanks all.

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[Prowler573 5,000+ posts]

What kind of vehicle?

Do the wires attach to your alternator via posts or is there a plug of some sort that could have become damaged?

 

[ghart999 10+ year member]

2002 Pontiac Grand Prix Supercharged

There is a small clip style plug that clips in underneath with a few 16G wires which is fine. The pos wire connect via post which is fine too. Especially after swapping the old alt in I am sure that all wiring is solid. WTF!!!

 

[CntInjaDisNinja 10+ year member]

My car is doing the same exact thing, it stalled on me when I was on traffic on the interstate the other day! I have a voltage gauge installed in the dash and it was going from 13.5 to the 11's. Im tempted to say it is the batt cuase it is gettin kinda old, but my car starts fina as well. hmmm

 

[Prowler573 5,000+ posts]

How old is that red top, ghart??

 

[ghart999 10+ year member]

How old is that red top, ghart??

about 3 years and 45,000 miles. IS that old?

 

[Prowler573 5,000+ posts]

Not normally for a gel cell but it might not be a bad idea to have it tested anyway. I know Denver is full of Auto Zones and they test for free //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[ghart999 10+ year member]

Alright I will have it checked tomorrow.

 

[CntInjaDisNinja 10+ year member]

Would a dying batt make the voltage drop like that??

 

[ghart999 10+ year member]

Batt is fine. I even swapped the batt from my wifes car in to make sure. Same problem. Someone mentioned it could be my mass airflow sensor going bad, so I am swapping mine out with a friend's over the weekend to see if that is it. This *****.

 

[CntInjaDisNinja 10+ year member]

^^^^hahaha ghart that is EXACTLY what I was thinking next. I have a Hot shot WAI on my car and I cleaned and oiled the filter and then about a week later the problem started. I think some oil got on the sensor. Im about to go buy some MAF cleaner at auto zone and see if that solves it.