Voltage issue

ViperPete

ViperPete

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OK so here's whats happening.

If I drive the truck and don't run the heater/headlights/ stereo the voltage stays at 14v with the truck at idle. If I run the heater/stereo/headlights or any combination of the 2 at idle the volts drop to around 12v. Once i start moving the volts rise to 14v.
The battery also does't fling the motor over like it used to. I think my alternator must be going bad and that's killing the battery.

Maybe it's time to replace the alternator but I don't want to replace it with another stock unit. Does anyone know of a higher-output alternator that will fit our truck?
 
Sounds like the alternator. Do you have a big stereo system or something pulling lots of amps? Of not I would just go with a normal alternator but thats just me
 
IronAffliction said:
Sounds like the alternator. Do you have a big stereo system or something pulling lots of amps? Of not I would just go with a normal alternator but thats just me
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I have 2 amps. 3 sets of Infinity Kappa Perfect Components and 2 10" subs. I also have HID headlights.

Def want more output if I can get it.
 
sublimeswinger said:
That is plenty for a stock alternator. your voltage sounds right , even with everything running
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The gauges and headlights dim at a stop light. That is not normal. It is not normal for the voltage to drop 2 volts with the truck at idle and to go to 14v at 1000 rpm or higher.
 
I would look for a rebuild kit if they are available. Prob a lot cheaper and its not hard to do.
 
Could be a loose belt. Confirm your tensioner is still strong and not seized. try a new belt then see what the voltage does..
 
Slitherbeast said:
Could be a loose belt. Confirm your tensioner is still strong and not seized. try a new belt then see what the voltage does..
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The belt is pretty new. I doubt its the belt as the alternator performs perfect above 1k RPM


earl lee said:
What brand of battery you using and how old is it?
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Not sure of the brand i think its Autozone brand. But it is at least 5 years old.
I'm gonna throw a new battery in it and see what happens before I look into an alternator.
 
you should do a draw test, and an alternator load test to be sure, just guesing is just that a guessing game,

but if you are running a couple amps, its more than likely having a hard time keeping up

get ahold of js alternators in sc, he has an upgraded unit that will work perfect for your set up.
 
ViperPete said:
The belt is pretty new. I doubt its the belt as the alternator performs perfect above 1k RPM




Not sure of the brand i think its Autozone brand. But it is at least 5 years old.
I'm gonna throw a new battery in it and see what happens before I look into an alternator.
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A new battery is cheaper than a alternator plus given the age of your battery its likely time to replace it anyway. Battery might not be able to hold a charge as well, putting a strain on the alternator.
 
I don’t post very often but thought I would chime in here as I’m experiencing similar symptoms. I installed an Optima Red Top battery a couple years ago and started experiencing very “sluggish†startups this past summer so I took it back to Auto Zone to get the battery tested and it checked ok. After discussing some of the same symptoms you mentioned, he did the load test Tony suggested and said the alternator was doing it’s job as well but said the truck was not producing the voltage it was supposed to be producing. After some digging it didn’t take long to learn, as I’m sure most already know, the voltage regulation is controlled by the computer. Hopefully yours is simply the alternator as there’s not many options out there for us. I’ve been researching a little and when mine completely lays down I may try to splice in an old school external voltage regulator instead of replacing the ECU. Anyways, good luck with finding your solution!
 
Got a new battery. The engine starts instantly now, but there is no difference when sitting at a stop light with the headlights and heat/stereo on. Voltage still drops to 12 and then rises to 14v when I raise the RPM.

Guess I need a new alternator that has more voltage at idle.
 
Are you running underdrive pulleys by any chance? If so, is the alternator just not turning fast enough at idle? Just a thought...
 
sleepersrt10 said:
Are you running underdrive pulleys by any chance? If so, is the alternator just not turning fast enough at idle? Just a thought...
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Yes i have an under drive pulley. I priced out a new stock pulley/tensioner/belt and its only a little more and i can get a 210 amp alternator. Might just go that route. My alt is 13 years old.
 
ViperPete said:
Yes i have an under drive pulley. I priced out a new stock pulley/tensioner/belt and its only a little more and i can get a 210 amp alternator. Might just go that route. My alt is 13 years old.
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Didn't know you had a under drive pulley, that with what is likely an original alternator is likely your problem

I was going to ask about the last time you changed your serpentine belt. I just changed mine with a new one, and noticed the old one had looked like it stretched itself an extra inch.

Putting belts on these trucks are PITA as well.
 
It will charge slightly less sitting still at idle, but in the years I had it on my truck and over a 150k miles, never caused an issue one. 12.5 at idle is perfectly fine. Will not cause slow starting! That's the battery. Many don't give it sufficient cranking Amps when buying new. 850-1000 I like to see.
 
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