Alternator trouble

[fritosaregood 0]

I installed a stinger voltage display in my car about a week ago. Since then ive noticed that ill be driving around and all the sudden the voltage will drop from 14.4 to 12.5~4. But if i change anythin power consumpiton in car, (i.e. rolling down windows, blinker, turning my lights on, a/c on. and also when i hit the brakes or change gears) the voltage goes back up to 14.5 for a few seconds and sometimes goes back down to 12.5 and other times it will stay back up at 14.5

I thought it might be my connections, so i hooked two DMM in my car. One run to my battery pos and neg, and the other run to my alternator + post to my battery neg. Once i was driving around again and noticed the voltage drop i turned on both DDMs and both their voltages read 12.5. so from that i concluded it isnt my alternator + connection, or my battery + connection.

I also dont think the alt has completely stopped producing power when my voltage drops to 12.5, because my voltage should be under 12 with the car running with no alt.

anyone have any other ideas?

[NB50 206]

How old is the belt?

[BKOLFO4 29]

If it is a newer vehicle, the alt may be regulated by the ECU. The voltage is regulated based on the need.

I have a friend that always turns his marker light on while playing his system so the ECU will ramp the voltage up on the alt.

My 2008 Silverado does that same thing, and it is all factory. . .drives me crazy.

Brian

[jonbearsmt 919]

the new dodges do the same from what i have read.

if its older... you it maybe youe exiter wire...

[fritosaregood 0]

drove to work after i posted, and hitting the brakes doesnt make the voltage go back up anymore,

and to clarify how i said change gears makes it go up..its automatic, and when i switch it to nuetral when im driving it goes back up to 14.5 and usually when i park it goes back up to.

the car is a 95, as far as i know the belt is as old as the car. Exiter wire?

and the alt. its one of the 200 amp iraggi amputators from ebay

[NB50 206]

I would change the serpentine belt, more then likely it is slipping. It is the easiest cheapest solution to start with and besides the belt possibly being 15 years old it is probably time to have it changed anyway.

Edited February 6, 2009 by bromo

[fritosaregood 0]

i think thats the first think ill try,

There is an alt shop around here and i talked to them before i got my h/o alt, and once i got it i showed them, and they told me the pulley is way to small. i took it up there again yesterday and he said that small pulley could be makin it slip too. but im goin to just change the belt first

Does anyone elses h/o alts have a small pulley, smaller than stock

pic

compared to stock

[ABXX49 20]

A smaller pulley WILL make the belt slip.

[NB50 206]

A smaller pulley WILL make the belt slip.

X2

Instead of getting the same size belt get a smaller belt when you buy a new one. There is probably a formula you can find on the internet to calculate the size belt you need for the smaller pulley.

[jonbearsmt 919]

i run an underdrive pully.... i never had a problem with slip..... but then again i do run a top of the line belt.. its so sticky!

[Quentin Jarrell 671]

Do you have extra batteries in your system. Like the others said the ecu is more than likely not seeing enough current draw keeping the alternator off until you draw more current. This is the reason Ohio recoments piggy-backing factory turn on wires, on a dual alternator setup when utilizing the factory alternator. So that their aftermarkets will come on only when the factory does.

Also, your voltage should not be below 12 volts when the car is off. It should be very close to 12.6 on a good battery.

Edited February 11, 2009 by Audibel Customs

[fritosaregood 0]

Do you have extra batteries in your system. Like the others said the ecu is more than likely not seeing enough current draw keeping the alternator off until you draw more current. This is the reason Ohio recoments piggy-backing factory turn on wires, on a dual alternator setup when utilizing the factory alternator. So that their aftermarkets will come on only when the factory does.

Also, your voltage should not be below 12 volts when the car is off. It should be very close to 12.6 on a good battery.

i have two extra batts, but i took them out along with my big system until a suspension upgrade.

but i have been thinkin along those lines but when i turn my system up the voltage stays at 12.5, but somethin like turnin on a blinker makes it goes back up.

as for voltage blow 12, i didnt mean when the car is off, if a car is on with no charging system the voltage will be under 12

[Quentin Jarrell 671]

I completely looked over the fact you have an aftermarket alternator. If the belt is slipping you will be able to see black rubber residue around the alternator pully. If not, I would re-install the factory alternator and see if the problem persists. That is if the factory alternator was in good shape to begin with.