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laprodigy001
07-06-2013, 08:31 PM
hello,

problem started a few weeks ago.i was going to walmart and i noticed the truck a tiny bit sluggish.i put on the AC and it was not really cold and lacking a lot.so i stopped to shop with wife and came out after being in there a few hours and my truck was dead.it turned over a half turn each time i tried and then nothing.if i turned my truck in the on position the gauges would go crazy.but barley any volts. and when i looked under hood seeing if there was a loose connection i noticed my neg battery cable was really hot and had a slight smell of sulfur from it.so i tried to jump it for a while and it seemed like it wanted to go but every time i turned the key everything would die out.so i tested battery and they said it had a dead cell and only showing 9volts.so i purchased a used one from a junk yard and it started right away.showing 14 volts on the gauge.i only used it 2 times in the past week.and yesterday when i would drive the volts would drop from 14 to one line under.when i was at idle it would go back to 14V.i had nothing on,not the radio,ac, or anything.so i parked car at my and went to start it the next day and nothing.the under hood light is so dim its barley noticeable.everything drained again.the first 2 times i started it it started but seemed like a weak start.but once it was on it seemed fine.
does anyone have any ideas.is there a way autozone/advance could check my alternator if i brought it in.and how accurate would that be.thanks

laprodigy001
07-06-2013, 08:32 PM
1998 gmc Yukon slt 5.7l 4x4

bowtie44s
07-06-2013, 09:32 PM
is there a way autozone/advance could check my alternator if i brought it in.and how accurate would that be.thanks

Why don't you check it yourself? Have the truck running. Turn everything on, radio, a/c, wipers, lights, high beams, hazard flashers, and put a multimeter on the battery. It should be 13volts or above. If that checks out good, unhook the positive battery cable, the alternator should keep the truck running, if it dies it's either too small or bad.

AZRon
07-06-2013, 11:26 PM
Why don't you check it yourself? Have the truck running. Turn everything on, radio, a/c, wipers, lights, high beams, hazard flashers, and put a multimeter on the battery. It should be 13volts or above. If that checks out good, unhook the positive battery cable, the alternator should keep the truck running, if it dies it's either too small or bad.




Why do you keep telling people to do this? It was somewhat valid on vehicles equipped with DC generators, led to mis-diagnosis on vehicles with alternators, and can become very expensive on vehicles equipped with computer-controlled emission systems.

Feel free to blindly poke, unhook, probe, and jumper anything on your own vehicle, but for the love of all things four-stroke, stop telling other people to do the same.

desrtrat
07-07-2013, 12:50 AM
have it bench tested. you could have a bad diode in there. also check/clean all your grounds. if all is good then i would do a draw test.

good luck

desrtrat
07-07-2013, 12:58 AM
unhook the positive battery cable, the alternator should keep the truck running, if it dies it's either too small or bad.
very bad advice...

bowtie44s
07-07-2013, 08:53 AM
Why do you keep telling people to do this?

Because it works. I have done it on probably a dozen computer controlled vehicles. Engine keeps running if the alternator is good. Have you done it and seen it didn't work? If not don't say it doesn't work.

laprodigy001
07-07-2013, 06:38 PM
I will be getting my alternator and battery tested at advance auto tomorrow and I will try and jump it after and see what happends.

ToyHauler
07-08-2013, 05:26 AM
Because it works. I have done it on probably a dozen computer controlled vehicles. Engine keeps running if the alternator is good. Have you done it and seen it didn't work? If not don't say it doesn't work.


your battery is the primary voltage regulator in the circuit, without it the voltage from the alt will spike to dangerous levels for all the electronics in the system.

ToyHauler
07-08-2013, 05:29 AM
I will be getting my alternator and battery tested at advance auto tomorrow and I will try and jump it after and see what happends.

you had one bad battery and likely another from the junk yard, they dont like to sit around and will go bad with no float charge. you also need to clean your battery terminals especially if you say you saw carbon or smoke. you need to clean both ends of each wire and make sure that pos braid is good. i replaced mine with real wire because it disintegrated in my hand

laprodigy001
07-08-2013, 11:04 AM
I looked in the back of my alternator and I notices yellowish dust on the back fins.also all the yellowish dust is on som e of the wires around there.what could that be.I will try and get a pic

ToyHauler
07-08-2013, 01:16 PM
could just be pollen or something, corrosion is local to the connection itself. i would clean your connections then after the trucks been running a while at idle with the accessories on should be around 13.5v at the battery with a meter

laprodigy001
07-08-2013, 04:10 PM
Truck jumped started right away.put a volt meter to it and it was read 13.8v.I put a load on it and it was still reading 13.does that mean my alt good.and what should the volts be when truck is off.

laprodigy001
07-08-2013, 06:43 PM
When I turned the truck off it was 12.45v...its been about 2 hours now and I just checked it and it reads 12.12v.....is that a normal drop in 2 hours.if the battery is messed up could it not hold a charge and drain over night.

bowtie44s
07-08-2013, 07:06 PM
your battery is the primary voltage regulator in the circuit, without it the voltage from the alt will spike to dangerous levels for all the electronics in the system.

I can buy that because the gauge does jump all over the place although I have done it on over a dozen carbureted and computer controlled vehicles and have never had a problem and it let me find a few dead alternators. The multimeter on the battery won't hurt anything though.

laprodigy001
07-09-2013, 01:07 AM
I tested it 6 hours after my last post and it dropped to 12v.so in a total of 8 hours it went from 12.45 right after I turned engine off to 12v flat.

bowtie44s
07-09-2013, 09:24 AM
I tested it 6 hours after my last post and it dropped to 12v.so in a total of 8 hours it went from 12.45 right after I turned engine off to 12v flat.

You either have a bad battery or a parasitic draw. Does your multimeter read amps? You shouldn't have any more than 50 milliamp with the truck off. I think mine is like 27ma.

desrtrat
07-09-2013, 10:49 AM
I tested it 6 hours after my last post and it dropped to 12v.so in a total of 8 hours it went from 12.45 right after I turned engine off to 12v flat.
if you are only louse .45v after 8 hrs, i would not consider that a lot. did you have your battery tested? you can have all the volts in the world, but if you have no amps being stored, then your SOL. have your battery load tested. you may have 1-2 cells going/are bad

ToyHauler
07-09-2013, 11:02 AM
sounds fine to me. you are not going to have much more than 12v with it sitting there for a while. you could try running it a while again and unhook the truck battery cables and see if it does the same. does it start the truck now? you have a separate battery charger you could hook on it to completely charge it?

laprodigy001
07-09-2013, 12:31 PM
Went and tried to start it and it had only 11v.and would not start.I took a video I will post soon

laprodigy001
07-09-2013, 01:13 PM
https://www.youtube.com/watch?v=3RzEN-NStR0

bowtie44s
07-09-2013, 09:34 PM
Can't watch the video, it's set to private. I haven't started my truck in 3 days and just for curiosity I checked it today and it was 12.4 volts. If your battery checks out good, set your multi meter to amps, unhook the negative battery cable and put one lead on the cable and the other lead on the negative post of the battery. Before you do this tape your door switch closed because you don't want your light coming on while you're doing this. The most you should see is 50 miliamps or .050 amps. Your clock uses a little bit and i'm not sure if the computer uses any for memory or not but still shouldn't be over 50ma. If you have more, start pulling fuses until it drops and that is your faulty circuit, you'll have to go from there.

ToyHauler
07-10-2013, 04:22 AM
check the above post. but its hard to tell if you have a battery if you dont charge it up all the way first. the alt at idle doesnt charge very much, so the easy thing to do is hook it to external charger

laprodigy001
07-12-2013, 06:52 PM
i put a ammeter on and it was reading 0.015...i also jumper my truck last night and drove it to charge my battery...i parked it and took both battery cables off and tested just the battery and it was reading 12.70v when disconnected.i left it undone and rechecked it 5 hours later and it went to 12.36 then rechecked in the morning and it went to 12.30.is that normal.my alternator makes some loud squeals sometime.could there be a short in there.and would a short show up on the ammeter when tested a parasitic draw.

ToyHauler
07-12-2013, 07:54 PM
sounds fine to me, except the alt making noise, but its likely a bearing in it or something like that

bowtie44s
07-12-2013, 08:09 PM
i put a ammeter on and it was reading 0.015...i also jumper my truck last night and drove it to charge my battery...i parked it and took both battery cables off and tested just the battery and it was reading 12.70v when disconnected.i left it undone and rechecked it 5 hours later and it went to 12.36 then rechecked in the morning and it went to 12.30.is that normal.my alternator makes some loud squeals sometime.could there be a short in there.and would a short show up on the ammeter when tested a parasitic draw.

The battery sounds normal, I'd leave it a couple days and check it again. Did you unhook the negative battery cable and put the leads between the cable and negative terminal? 15 miliamps is fine so that's not your problem. What did you say the voltage on the battery with the engine running was?

laprodigy001
07-12-2013, 08:57 PM
when the truck is on with no load its in the high 13s low 14s..when i have a load on it its low 13s...and the noise started when i was doing my power steering pump i forgot to put the return hose on the pump and had it facing up so when i started the truck the fluid just shot up.and after that i hear a loud screeching sound sometimes last for a few seconds others a minute or so...i was just wondering if maybe it got shorted and maybe taking power...if i had a bad diode would it show up when i test the draw with the ammeter..

mechacode
07-25-2013, 09:34 PM
Had the same thing happen to a customer's truck, he fried his starter cable on the exhaust manifold. Hot cable=major drain, probably a short.

TAA-HOE
07-26-2013, 05:31 AM
I have one of these on mine
http://www.prioritystart.com/
Saved my battery when I couldn't find the parasitic drain, and saves it when I leave the lights on.

shakesvho
07-26-2013, 11:18 AM
I have one of these on mine
http://www.prioritystart.com/
Saved my battery when I couldn't find the parasitic drain, and saves it when I leave the lights on.

that looks nice, how long u been using it

kemble
07-26-2013, 12:21 PM
Have the battery load tested. But to me the battery sounds iffy. I would want 13 volts disconnected from the vehicle.