Hello, so a few days ago my alternator just up and quit on me with no warning, i was driving along at the usual 14V on the volt gauge when the battery light came on then a few seconds later the volt gauge went down to around 12V and all my lights dimmed. so i turned off the radio and the fan and tried to limp home. The truck ran out of juice about 5 mins away from my house. after leaveing jumper cables on from a running car for about 25 mins i was able to start it and get it to my house just as it died again. the next day i went and got the alternator tested and it was confirmed bad on dc volt output. so i got a brand new rebuilt for $199 and tax installed it and jumped the truck and it started charging. the volt gauge on the dash read just under 14V and no matter what engine speed it never quite reached 14V.

after letting it run for about a half hour i shut it down. later that day i went and drove it for the first time, and i started noticing that the volt gauge was dropping to around 12 then going back up to almost 14 kinda bouncing as i accelerated and the battery light would come up for a few seconds then go out then come back then go out then it would be out for a while and the volts would stay at almost 14. but every time i accelerated away from a stop the same thing happened and at night i realized that my headlights and interior lights were pulsing as i accelerated but would return to normal once at speed or at idle.

Do you think that i just got a faulty alternator or is something else gone wrong on my truck. the alternator before was stronger then this one the gauge rarely ever dipped below 14V and then all of a sudden just died. and my new one never even makes it to 14V and i Got the 105 amp one.

thanks for any comments or suggestions

Dave

EDIT: My truck is a 2000 Jimmy 2 door

and other electrical issues i have been having may or may not be related:

atc fuse blowing randomly without using the 4x4 buttons

gas gauge dances all the time

blinker relay clicks randomly without activating lights sometimes clicks slowly sometimes clicks like mad.

 

so i just went for a drive today and the alternator is now sitting at 14V consistently with no noticeable pulsing of the lights or the volt gauge (only went for about a ten minute drive) but the charge light still comes on and off even tho the volts stay constant at 14???? any ways i took a video to show u whats going on... sorry bout the poor quality it was from my loner phone (i ran over my nice one lol) (and ignore the audio i dont know why but this phone cannot record audio to save its life believe me that noise is not what i was listening too lol.

 

Take the alternator back & get another one. Twice so far this year I've seen where we didn't get a good rebuilt alternator until the 3rd one and one alternator that lasted two weeks. There's an issue with parts quality right now. (anyone want to buy some Chinese drywall? Cheap!). That being said, be certain you tightened the rear wire and check the side connector for corrosion and/or damage. An intermittent connection would give you charging problems and damage the alternator. Your fuel gauge is probably the result of a common problem of a bad sending unit on the fuel pump. The blowing ATC fuse: even though you never change ranges your truck cycles the transfer case between 2WD drive & 4WD each time you start it as a self test mode, hence the buttons all flash when you start it. It may be a wiring problem, it may be a bad ATC controller, it may be a bad transfer case motor shorted to ground. Mine corroded on the side against the case resulting in water intrusion in the sensors. But an ATC problem shouldn't affect the charging, that's why there's fuses.

 

so its pretty much the alternator no matter what then? nothing on my truck can make this happen?

 

The description of your problem reminded me exactly of what happened on my uncles pickup truck. First replacement rebuild didn't work, second replacement worked for two weeks but ran a volt lower than the original then the light came back on, third one has been working right for 3 months now. Something on your truck COULD make this happen, but I just know there's been a bad run of parts, had a problem with two different rebuilders (our NAPA uses two different rebuilders and I saw both names on the boxes going through this). As far as wiring on the alternator, it's very simple, big red one on the back and the small one on the side. The big red one is pretty much all or nothing. That little one is connected to your PCM on the fender which sends a Pulse Width Modulated signal to the regulator inside the alternator, it adjusts the charging voltage based on underhood temperature. The PCM also sends a Class 2 signal to illuminate the charge light if there's a problem with the charging system. Not like the old days where the battery light on the dash was wired directly to the alternator. I'm just trying to say (after all that) based on my recent experiences it's most likely you need to try a different alternator.

 

well i got another rebuilt alternator and my battery light has now stopped flashing and my lights no longer flicker, but this one doesn't make the voltgauge on the dash read a full 14V like my original did and like the first rebuilt did sometimes, but when i test it with a multimeter it says 14.5V. so i am happy... thanks for the response hopefully this lasts longer then the 2 weeks your uncles did

 

Fortunately the store manager is a personal friend so it's just time, no grief on parts returns. You should get the battery tested just to make sure it's good, a battery starting to go bad will put a constant drain on the charging system. Don't count on a factory guage to be accurate, the important thing is that it's consistent. When they start doing something unusual that's when you pay attention. Glad it's working now.

 

yea my battery is still pretty solid it had taken a beatin but its good lasts a long time and the eye on the battery is still green