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Really stupid alternator question

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90K5

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When my truck is just idling, the voltage drops to about 8 on my stock gauge, and the lights dim a lot. Once I give it any gas at all though, it goes back up to 12-13...had it tested at AutoZone and they said it was fine, but they tested it at 2000 RPMs...this first showed up about a month ago, truck died when going real slow and wouldn't restart, battery was dead...hasn't happened since, but lights still dim and volts go down...so, is the alternator going bad, or what...its under warranty, at autozont unfortunately...thanks
 
My first real job was rebuilding alternators. Sounds to me like you need a bigger alternator. Kits are cheap, and very easy to install. Get a high output kit. I think that should solve your problem. With out checking your alternator out on the equipment I used, I wouldn't be able to tell you whats wrong with yours.
 
I would say you are needing an alternator. With all accessories turned off you should be able to maintain at least 12 volts. Take your truck back down to AutoZone, they should have a tester that will be able to test the system while the alternator is on the vehicle. If not, take your hand held voltmeter in with you and show them whats up.
 
I dont have an accessories that draw much power, and i think my alt is a 105 amp, just need to to test bad so autozone will honor warranty...maybe ill go the the other autozone tomorrow...
 
This happened to me once. I thought my alternator was going bad, and had it tested, but it actually was my battery dying. Once I got a new one, everything went back to normal.

Last year my alternator did go bad. Voltage started draining slowly and didn't increase even if I revved it up.
 
I have the same exact problem right now. My altenator is only a week old. The reason I replaced it was because the voltage regulator went bad. I had to run it about 100 miles with it charging 18+ volts. Do you think that ruined my battery causing my new problem? My other guess was that the belt could have been loose causing it to slip at low rpm but mine isn't you may want to check yours. Are there any more suggestions out there.
 
Usually when a battery overcharges the sides will pooch out.

One time I saw this ford with a brand new battery. They had only driven on the battery for about 3 or 4 miles and the sides had expanded about an inch. It turned out their volt. regulator was out.
 
if you ask that they give you anether alternator,they should give you one.i had one i bought and they rebuilt it wrong with the diode facing the wrong direction so power would always be on and no power would go back to the battery.the second one only charged at 12.2 volts and wasnt enuf to keep up with voltage drain.they said as long as it was charging over 12 volts then the alternator was good.i said i did not want that alternator so they gave me anether one.that one worked right and chaged at 13.4 so in the end i got what i needed.id say tell them you want anether alternator or they might loose your business.the customer is always right and if they dont believe that maybe the other autozone might.some places just dont get it.
 
Hey bud
I work at Autozone. I'm at my second store now since moving. Here is the deal...if someone works there with the least amount of sense...ask them to do this.
1. Test your battery in vehicle. (you need to make sure it's fully charged for a proper alternator test...so charge it then drive it there)
2. Test voltage at idle. The traditional alternator tests work at 2000 rpm like you said and at idle as well.
3. Make sure they note the voltage at idle...this should be plenty of enough cause to return an alternator.

This should cover you....if they they dispute you they are morons, plain and simple. Try another AutoZone.
Blake
 
Same thing happened to me and it was only a loose belt. If it is the alt you can have it rebuilt pretty cheap.
Joe
 
I fixed mine tonight. Changed the alternator again. I don't know what was wrong with the other one but O'reilys changed it out for free.
 
your first mistake was to buy it from autojunkzone i used to buy my parts there but i learned my lesson along time ago sure they have alot of lifetime warrantys on most of there parts but who wants to spend there life changing them . i have in the past carried parts that i bought from them to them to be tested they always said its not bad but they were wrong everytime and i am sure alot of you other guys have had the same thing happen i guess i am just ranting but at least i have learned my lesson you get what you pay for . well to get to back to your ? yes your alternator is no good carry it back and tell them you want another one or do like i did go ahead and buy a good one somewhere else and take it back and tell them you had to have one then and tell them you want your money back. and there is one way to see if your alt. is charging take the postive cable off with your truck running if it stays running that mean that its working if it dies rite away the alt . is not charging
 
When I bought my truck I had some similiar problems. Turns out the altenator belt was completely glazed!Never heard a squeek from it but the damn thing slipped like goose crap. I replaced the altenator with another I had laying around and it did the same thing - charge alittle at idle, sometimes nothing. Changed the belt on a "Do ya think?" Low and behold charging problem gone /forums/images/graemlins/smirk.gif
 
An easy check for the glazed belt problem is to grab the cooling fins on the alternator (with the engine turned OFF, of course!) and see if you can turn it by hand. If it will turn, then the belt is glazed and useless. Don't do this just after driving, as the slipping will make the pulley and alternator <font color="red"> HOT</font color>! /forums/images/graemlins/shocked.gif
 
Yeah, i actually never buy anything but oil and stuff from AutoZone, this alternator is a few years old, got it there when i didn't know that much about trucks...it is the only thing i have from Autozone on my truck though, everything else is NAPA.
 
Turns out it was the ground. The screw fell off the firewall i guess, cause it was just hanging there...
 
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