Low voltage problem, not your tpical one either. Please help!
Low voltage problem, not your tpical one either. Please help! Ok, I picked up an 02 trans am last year, 19k on the clock NO UNDERDRIVE PULLEY...when i picked it up the first issue was...
First Alternator: GM Rebuild. Voltage was always low but fluctuated all the time, as in at idle my headlights looked like strobes almost and even my gauges would dim and get brighter, like every .5 seconds, like my alternator was camming almost.
Second Alternator: GM Rebuild. Lasted for 5 days so no real input here.
Third Alternator: NEW Duralast gold, not rebuilt. Lasted for 5 months (died cause I jumped 2 cars in 2 days I guess, damn my friends!) and heres what it did for the 5 months I had it....In the morning (or night) whenever I first fired up the car for the day, voltage was where it should be, a nice 14.7, no matter WHAT I had turned on, including the defogger. Now, after 10 min of driving, the voltage would ALWAYS drop to low 12's with JUST my radio on (stock monsoon btw no subs). If I reved the car, the voltage would go up and then drop to like 11 and then come back up to the 12's. I also checked this with my radar detector which shows voltage, not just the stock gauges. If im on the highway, it stays at roughly 13.8 due to being at 2k rpm.
So the problem is, everything looks good and works fine until about 15 min of driving, and then it acts all jacked up till the next day. The car "runs fine" but its obviously not right because as I accelerate from a stop everything gets brighter and the voltage gets CLOSER to normal.
Oh and I tried 3 different batteries, one out of another car I own which IS acting perfectly normal.
Any ideas?
First Alternator: GM Rebuild. Voltage was always low but fluctuated all the time, as in at idle my headlights looked like strobes almost and even my gauges would dim and get brighter, like every .5 seconds, like my alternator was camming almost.
Second Alternator: GM Rebuild. Lasted for 5 days so no real input here.
Third Alternator: NEW Duralast gold, not rebuilt. Lasted for 5 months (died cause I jumped 2 cars in 2 days I guess, damn my friends!) and heres what it did for the 5 months I had it....In the morning (or night) whenever I first fired up the car for the day, voltage was where it should be, a nice 14.7, no matter WHAT I had turned on, including the defogger. Now, after 10 min of driving, the voltage would ALWAYS drop to low 12's with JUST my radio on (stock monsoon btw no subs). If I reved the car, the voltage would go up and then drop to like 11 and then come back up to the 12's. I also checked this with my radar detector which shows voltage, not just the stock gauges. If im on the highway, it stays at roughly 13.8 due to being at 2k rpm.
So the problem is, everything looks good and works fine until about 15 min of driving, and then it acts all jacked up till the next day. The car "runs fine" but its obviously not right because as I accelerate from a stop everything gets brighter and the voltage gets CLOSER to normal.
Oh and I tried 3 different batteries, one out of another car I own which IS acting perfectly normal.
Any ideas?
Also the third alternator was put in 2 days ago, it did this from the second it was put in. Every alternator has acted like this. I realize its not the alt, hence me asking if you guys have any ideas. It cant be the wire coming from the PCM anyways because it IS charging, its jut not ever getting enough voltage from the alternator itself. The wire tells the alt to charge or not, not to charge like a little girl, which is what its currently doing.
Last edited by Camaro_Zach; Jun 4, 2008 at 01:32 PM.
Does your car have a aftermarket cooling fan tune? My old trans am had a tune that turned the fans on high speed at 180* and it caused the voltage to drop way down... got it retuned with a higher setting and the voltage stayed 13+
not the alternator, something fishy happening. my brother had the same problem in his truck, went through batteries and alt. every month. he had his electrical system load tested and found that he had a ground that had been draining his system. not sure what excactly he had found. so check grounds and starter wires for breaks, i guess. not much help here but might give you a new idea.
Not the fans, stock car, stock tune. This isnt a slight draw, fans should not ever effect the car on this level. And def not the alternator. I am just going to do some trouble shooting to night and make some temporary "home made jumper cables" and see if I cant bypass the stock harness and see if I cant get my voltage back up again. It might be the fusible link in the harness thats causing me my issues. I will post back up tomorrow with some info.
Staging Lane
Joined: Dec 2007
Posts: 92
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From: odessa, tx
Not the fans, stock car, stock tune. This isnt a slight draw, fans should not ever effect the car on this level. And def not the alternator. I am just going to do some trouble shooting to night and make some temporary "home made jumper cables" and see if I cant bypass the stock harness and see if I cant get my voltage back up again. It might be the fusible link in the harness thats causing me my issues. I will post back up tomorrow with some info.
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Well I made an alternator jumper cable if you will, 10 gauge, directly from the alt to the battery in addition to the existing cable, it did nothing. I disconnected the end from the battery and used the volt meter, the alt is only outputting 13.8 at best, so its not even attempting to be in the 14's where it should be.
The only thing I can think at this point is its the pcm or the wire itself in the harness somewhere that tells the alt to charge.
Again today I started the car, turn ac on full, radio on, head lights on, AND the defogger and it wouldnt drop below 14.3, start driving, 5 min later its in the 12's at best.
Anyone else have any input on the matter?
The only thing I can think at this point is its the pcm or the wire itself in the harness somewhere that tells the alt to charge.
Again today I started the car, turn ac on full, radio on, head lights on, AND the defogger and it wouldnt drop below 14.3, start driving, 5 min later its in the 12's at best.
Anyone else have any input on the matter?
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Yeah I agree, I forgot to mention that I was going to attempt this over the weekend, because besides that, I am running out of ideas to be honest. Its so clear the car is down on voltage too because the shifts feel weaker and the car feels a bit slower when the volts are down, its sad that its noticeable like that.
My 2001 SS had a low voltage at Idle only would drop to around 12.1 but once I start moving it would go back up to 13.8/ 14.0. Only when the car was in drive at Idle. Ended up being that wire was bad. I good not find the problem so I had to take it to the stealer ship and they ran another wire and the problem was fix. That wire is so small I can see why it causes so much issues.
My 2001 SS had a low voltage at Idle only would drop to around 12.1 but once I start moving it would go back up to 13.8/ 14.0. Only when the car was in drive at Idle. Ended up being that wire was bad. I good not find the problem so I had to take it to the stealer ship and they ran another wire and the problem was fix. That wire is so small I can see why it causes so much issues.
Actually, which wire off the PCM is the one I want to re-run?
http://chevythunder.com/1999-2002%20...%20pinouts.htm
I cant find it by any of the normal things it would be called, exciter, alternator, charge, etc.
NEVERMIND found it. They think an alternator is a generator...nice haha
Red PCM Connector
Pin 15 RED Wire Circuit number 225 Generator Turn ON Signal
http://chevythunder.com/1999-2002%20...%20pinouts.htm
I cant find it by any of the normal things it would be called, exciter, alternator, charge, etc.
NEVERMIND found it. They think an alternator is a generator...nice haha
Red PCM Connector
Pin 15 RED Wire Circuit number 225 Generator Turn ON Signal
when i had charging problems with new battery/alternator, my fix was a new wire, but another thing that it could be are the 3 main grounds for the car...theres the battery ground, the one on the drivers side head (rear) and the ground that connects to the block at the end of the harness (two ribbon wires)
No good 
I did a resistance check on the wire, its good. So thats not doin it. I guess I will have to check the ground in the back of the head as you said. *sigh* I hate electrical issues like this. And the dealership wont give me a hand because the voltage is "within parameters" meanwhile Im on alt #4 in 1 year lol. Right. I cant wait to get stranded in this car!
I did a resistance check on the wire, its good. So thats not doin it. I guess I will have to check the ground in the back of the head as you said. *sigh* I hate electrical issues like this. And the dealership wont give me a hand because the voltage is "within parameters" meanwhile Im on alt #4 in 1 year lol. Right. I cant wait to get stranded in this car! 
