Voltage drops

[Puggsley456]

Hey guys! I have a 94 cutlass Sup(4door) 3.1L.

 

I have a hefty stereo system in my car drawing around 800 watts in total. I have had my alternator rebuilt to 137 amp output and I have rewired my entire charging system and grounds in addition to the factory wireing with 4 guage wire and put an optima red top in. But my votage guage on my dash still drops below the 13 volts line on the guage and If I sit at idle( in drive only) the voltage wont come up above the 13 volt line on the guage even with the stereo turned right down until I rev it up. But in park it stays above that line and dances around.

 

I just wanted to know if anyone else has had similar problems. I am starting to believe that it is the guage and not the charging system!

[musthavemuzk]

wellllll

 

so many places to go with charging system issues and a system.

 

so i will just throw a bunch out there and go from there.

 

how many amps?

what power?

what size of power wire from amp( or distro block) to battery?

what size of ground wire from amp to car?

did you clean rust and paint from the ground contact points?

what wires under hood did you upgrade? at minimum you should have upgraded the batt to car.

preferably the big 3 which is the batt to car ground, block to frame ground, and alt to batt positive.

 

proper fusing?

wires secure in the amps, at the batt, at the ground points?

ground wires need to be the same size or larger than the positive wires.

 

when the alt was rebuilt to 137 amp was the pulley changed to raise amp output at idle?

 

there are some starter things.

 

holla back with more info to help better

 

Monty

[Puggsley456]

Sorry for the lack of info. Heres what I can give ya:

- I have 1 - Pg ti600.2 which puts out around 700rms

- I have 4 guage wire everywhere, including power, ground and big 3 upgrade

- when I did the big three i cleaned the factory ground points just incase.

- fusing from batt to amp is 100amp and fuse from alternator to battery is 125amp.

 

But I never thought about changing the alt pulley! I think thats a good Idea!

 

But the one thing I was never really sure about, I ran the ground from the chassis to the front dog boned shaped engine mount and I was never sure of that location as a proper ground. What do ya think? Heres where I attached it but now I used 4 guage instead of 8:

[tloftus]

I'm no expert, but I'm pretty sure that's not a great ground. I jump start my car from there, so it definately works, but it'd be best if you can put it on one of the existing grounds on the frame or even just to the body of the car.

[THe_DeTAiL3R]

You say it bouces around when you are at a stop.... my guage bouces around with the signal lights flashing this is perfectly normal. With my stock alt, stock wiring my guage only "bouces" if I have my lights on at night and the stereo is pumping as hard as I let it go.. (460wRMS bridged Kenwood amp powering a 12" 500w Pioneer, and 40wx2 amp to the door speakers in addition to the CD player powering the dash and rear..)

[rudefyet]

137 amps should be plenty

 

like musthavemuzik said...check the pulley size

 

and also i'd be worried about the connection between the alt and the battery....i think the stock is only about 8 gauge

[Puggsley456]

You say it bouces around when you are at a stop.... my guage bouces around with the signal lights flashing this is perfectly normal. With my stock alt, stock wiring my guage only "bouces" if I have my lights on at night and the stereo is pumping as hard as I let it go.. (460wRMS bridged Kenwood amp powering a 12" 500w Pioneer, and 40wx2 amp to the door speakers in addition to the CD player powering the dash and rear..)

 

It bounces around when I am in park....and even then after a while it goes below 13v on the guage and stays there. In drive when I stop it drops into the red then when i drive away it pops back up again. I always thought it was that my idle was somehow to low. But changing the pulley to a smaller one would solve that.....I think.

 

137 amps should be plenty

 

like musthavemuzik said...check the pulley size

 

and also i'd be worried about the connection between the alt and the battery....i think the stock is only about 8 gauge

 

I have a second power wire(4 guage) running from my alternator to my positive terminal with a 125 amp inline fuse 12 inches from the battery.

[Puggsley456]

oh and by the way guys... this is my 4th alternator in 3 1/2 years.

[THe_DeTAiL3R]

DO YOU HAVE THE RIGHT SIZE SERPENTINE BELT????

[Puggsley456]

DO YOU HAVE THE RIGHT SIZE SERPENTINE BELT????

 

Ahhh! Ahhhh! ok......I wasnt expecting that one. Its been on there as long as I've had the car so I have never even thought twice about it before.

 

should its size matter? Because as long as its the right width the tensioner should take up the slack for the most part right?

[THe_DeTAiL3R]

should its size matter? Because as long as its the right width the tensioner should take up the slack for the most part right?

 

It *should*.. but what if the tentioner isn't working properly and the belt is either too tight or too loose? Just throwing ideas I've never actually had that problem (yet )

[SigEpCutlass]

You say it bouces around when you are at a stop.... my guage bouces around with the signal lights flashing this is perfectly normal. With my stock alt, stock wiring my guage only "bouces" if I have my lights on at night and the stereo is pumping as hard as I let it go.. (460wRMS bridged Kenwood amp powering a 12" 500w Pioneer, and 40wx2 amp to the door speakers in addition to the CD player powering the dash and rear..)

 

yea i get a slight fluctuation aswell it's common

[Canada]

Why do you think below 13 volts at idle is bad? What exactly do you have for system voltage at idle? You're try to track down a problem that doesn't exsist. The reason why you don't have 13 volts is because of the huge ass stereo........13 volts is just fine........hell, at idle I'd even settle for 11 volt if the stereo was on. PCMs and other mopdules usually don't start shuting off until 9.8 volts.

[musthavemuzk]

dp ya have a friend and a volt meter?

 

if so do some investigating.

have your friend sit in the drivers seat or vice versa.

and check voltage reading

car in park at idle system on and off

car in drive brake on system on and off

test at the battery and at the amp

 

this way you will know if the gauge is ok or not

and if it is bouncing the same or dif than the volt meter.

 

i have only had my ub3 cluster in for a couple weeks now.

this is the upgraded digital cluster with volt, gas, oil, temp, tach, speedo and odometer.

i have not noticed any bouncing of the gauge.

i have 1100 watts to front and sub.

stock alt

ac delco platinum batt

2/0 wire to trunk and distro block

appropriate size to amps

amps also have a distro block with 2/0 from it to frame

batt to frame and block to frame are good. have not done alt to batt yet.

 

of course i am not a bass monkey so volume is kept in check.

 

have ran as must as 1500 watts daily with no dimming or anything odd.

 

have killed one alt.

 

from what i remember alts are common with the w-bodies.

 

i would choose a dif ground point. while it is good and is used when jumping cars..not ideal.

 

here are some of my pics

http://www.dbfanatics.com/forum/photo_album_cat.asp?sqldtl=16

 

Monty

[digitaloutsider]

oh and by the way guys... this is my 4th alternator in 3 1/2 years.

Stop buying cheap rebuilt ones and buy Remanufactured or New. Also.. welcome to owning a W-body..