alternator stops working randomly
 

lately my alternator just stops working, i will be driving along and my volts will be at like 10-12 volts. it first started when i was towing my buddies boat and i backed it into the water then pulled it out. i thought maybe it was shorting it out or something. but then it started happening just randomly. i took my alternator back to napa where i bought it and had them test it. they said it was fine and putting out 15 volts. so i cleaned all my terminals and made sure everything has a good connection. it worked well for a couple of days but now it is screwing up again. today i was looking at houses and i noticed my volts were gone. so i disconnected the plug and the ground like i have been doing to fix the problem. then ten minuted later when i was going down the e-way it screwed up again i have a 145 amp alternator from napa and a red top battery, both are under a year old and have very little use because i rarely drive the truck. anyone have any ideas on what it might be, im clueless and its really starting to piss me off because i dont want to be left stranded anywhere. thanks

check all your grounds, make sure those are clean and tight. do you feel or see any surges when the voltage drops?

Also, closely inspect all wiring you can. You may also want to have an engine scan done, to make sure everything else is performing normally.

truck runs good, cant tell when the alternator stops working. i usually notice it when i get in my driveway and try and roll up my windows and they go super slow. then i looks at my volts and there is none because the alternator stopped working.


i will check all my grounds again.

will anything show up if it doesn't throw a check engine or a code?

if the alt was bad and voltage went to zero the truck wouldnt run good... it wouldnt run at all...... did you ever consider problems with the gauge itself?

i don't think it is the gauge. because the things the draw a lot of power(windows) bairly work when it has no volts. but other then that you cant even tell that the alt isn't working because all it is doing is draining the battery.

I'd say it's entirely possible to get a code, even if the light never came on. It may depend on the scanner used though.

With the way you've described the problem, it seems you have either a faulty ground, or a hot wire somewhere may be chaffe'd through and rubbing at times. The ground is the most common problem. Be sure no ground wires are attached to any painted surface and that they're clean and tight. Not that you haven't, but it's worth triple checking to rule it out. I can't tell you the # of times I've found that to be a problem on vehicles over the yrs, and I'm not even a mechanic!

Find out what kind of regulator they put in that alt as well. 99 and 00 trucks had a 2-wire setup, just a charge wire and and an energize wire. 01 and up have a 3-wire setup, one charge wire, one energize wire, and a PWM reference wire so the PCM can monitor the state of the alternator. If you got an 01-up alternator it will not work correctly in your truck. You need one that has an internal voltage regulator.

the truck would still run fine. i did 3 or 4 track passes without the alternator. after a pass or two my message center threw up a picture of a battery.

i will call napa and see which alternator i got. the thing is i had it on the truck since january and no problems till recently.

txsilverado- it seems like the alternator still works or something because a battery light never comes on. and sometime i will drive it for like 3-10 miles with no volts.

"no volts"?? as in - the guage doesn't even read 12?

If you pull the accessory belt and start the truck, your guage should still read 12 volts from the battery. If you are reading ZERO volts, as in, the guage isn't registering ANYTHING and your truck is still running, you have a problem in the cluster or the circuitry that measures the voltage. Your truck will NOT run on ZERO volts....


EDIT: my cluster will read 12 volts and throw up a message saying "battery not charging" or something to that effect, when I pull the alternator belt and start it.

sorry yeah it does read 12 volts but thats it it doesn't show it is charging or anything

ok i cam to the conclusion that something is getting wet or something because i washed the truck today and after that it screwed up.

Maybe you need a new belt?

Voltage Issues
 

I have noticed the same damn problem after I switched to a 6 speed. The only thing I can think of that I have not changed yet is the belt. It trans fluid on it and was slipping so I drenched it with brake fluid. But now I have changed to a 160A alternator and the problem is still there. I notice when I am driving my voltage goes from 14.8 to 12.6 and stays there. In the morning my lights flicker slightly and it is driving me crazy. Last night my friend suggested that the belt could be just done because of the trans fluid getting on it. :bang:

battery topped off? . . . any rust around the battery tray?

It is a 2006 truck with 6K miles on it. The belt is my next swap. :bang:

Since it's an intermittent problem, I'd be leaning toward a wiring issue. You may have a wire that's broken inside the insulation and loosing contact. I'd trace the wires that go to the alternator and do either voltage drops or ohm readings while performing "wiggle" tests on the wires/harness.

Much appreciated. I changed the belt and so far so good but, I will do the voltage test to mkae sure everything is testing properly

Did you ever track down what the problem was? I am literally having the same problem. I hauled my cousins boat, put the boat in the water. Pulled out and now I have been having the same issues for the last week now.

you do realize this is a 8 year old thread?