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.