Low voltage do I need a Alternator

JonBoy

Active Member
Joined
Mar 20, 2005
Location
Hampstead NC
Low voltage on my dash gauge around 10V and batt light was on while running ac on. (truck hasnt been run in a week or so) about 15 min into driving it it made its way to 12V and I soon turned off the AC and it made it to 14V. Now when I start it up it will go to 12V and slowly make its way to 14V over several minutes. Im thinking that my alternator is slowly going bad? when the trucks running that dash gauge shows what the alternator is putting out right? Also its a 98 chevy with a 5.0 130k miles and the batt is only a year old and seems fine.
 
what kind of vehicle ? If you are going by the dash gauge, they are usually pretty slow to respond, and sometimes not very accurate. verify with Digital Volt meter at the cig lighter socket ( while someone else is operating vehcile undersame conditions ) or have one of the Vatozone stores check the battery /charging system.

That your voltage is actually coming back up could mean the BATTERY is on it's way out. starting the vehicle is the highest load it sees (200-500amps pulled just to turn engine over), (unless you have a big stereo ) and the charging system might could be trying to get things back up to par after the start.

A weak battery will show this condition.

Kevin
 
just went outside to check it

Batt at 12.6V

Started truck and it went up slowly about 3 min to 14V

Turned on all lights and hi beams and in a 15 min time its at 12.5V

Turned all lights off and in 5 min reutrned to 14V

Shut off and batt dropped to 13.5V and slowly dropped down into the 12V range.

Is that normal or is my altenator getting weak?
 
JonBoy said:
just went outside to check it

Batt at 12.6V

Started truck and it went up slowly about 3 min to 14V

Turned on all lights and hi beams and in a 15 min time its at 12.5V

Turned all lights off and in 5 min reutrned to 14V

Shut off and batt dropped to 13.5V and slowly dropped down into the 12V range.

Is that normal or is my altenator getting weak?
Click to expand...

This was at idle ?

yeah, I'd say fairly normal at idle, most alternators do not charge rated capacity unless engine is at a higher rpm range.

WHAT vehicle are we talking about? Any idea the amperage of the alt?
Could also be grounding issues, poor cable connections, loose belt(s) even a bad sensor can cause high amp draw.

To many variables with out knowing vehicle, alt amperage, engine and aftermarket add ons.

That the alt is actually reaching 14v tells me that it is working.

Give us more info.

Kevin
 
its a 98 chevy k1500 with only the 5.0 I do have a amp but its not that powerful so im thinking its not taking alot of juice to run it. Also altenator should be a 105 amp one.
 
JonBoy said:
I do have a amp but its not that powerful so im thinking its not taking alot of juice to run it.
Click to expand...


AC clutch, blower motor, headlights, engine, ECM, radio,dash cluster, wipers, add up to about 40-80 amps drawn total, throw in the extra for the amp ( it still draws power, no matter the size ) and recovery time will take a little longer.

I ran into this with a customer last year, 2003 Silverado, power everything.

Customer complained the truck would just die while he was doing his paperwork/working on his laptop on job site. battery dead

started truck, alt was charging it ass off, drove it around, everything was normal. amps draw showed normal.

When I saw the cable and noticed the radio was not factory. looked under the rear seat, 2 1500 watt amps and a 1200 watt power inverter. Dash unit was a DVD player flip out.

BestBuy told him his stock 105 alt was fine for running all that stuff. ( wanna bet )

'03 truck requires 75 amps just to run. not much left for anything else.

it does sound like the Alt is working, just taking a bit to recover.

unless you can load the alt down and check the amperage output, you'll not really know for sure.

K
 
SOunds as if the old Alt was draining when not running. Can really fool you. Glad you got it working right
 
Back
Top