Another alternator problem... help me trouble shoot please.
Thread Starter
TECH Apprentice
Joined: Sep 2011
Posts: 344
Likes: 1
From: La Porte, TX
Another alternator problem... help me trouble shoot please. Hey guys, last Friday night on my way home from the local car meets I noticed my voltage gauge on the dash was riding on the orange. So I rush home trying to make it there before my car completely died, as I finally turn into my driveway my car starts sputtering and check gauges light, service vehicle light and ABS INOP lights are all on and it finally died (gauge showed 8v). That night I put my battery on a trickle charger because it had completely died(the battery was bought last year 10/12) The next day I replace the alternator with a new one from orielly's because the other one I had bought a year ago had lifetime warrenty. I was sure to have the bench test to make sure it works, it passed, I also bought and replaced the excitor wire and plug that goes into the top of the alternator.
So after all of this, when I first start my car it charges normally?(13v+ on the dash) then maybe after 5-10 min later down the road the needle starts slowly going down under 13v to where the point its resting just on where the orange hash part of the gauge begins maybe 11-12v. Now I just checked my battery with a multimeter and I got 12.85v with the car off and 12.3-12.5v with it running. I also tested where the positive cable meets the fuse boxes with the same results.
I'm just stumped to what the issue could be? a bad gauge? bad NEW alternator that tested good? or a bad battery even though its only a year old? I also have a hot wire kit for my fuel pump AND a very small system(10"sub with a 200watt amp) hooked up to the positive battery post at the fuse box but I've never had this issue before.
any help is appreciated.
So after all of this, when I first start my car it charges normally?(13v+ on the dash) then maybe after 5-10 min later down the road the needle starts slowly going down under 13v to where the point its resting just on where the orange hash part of the gauge begins maybe 11-12v. Now I just checked my battery with a multimeter and I got 12.85v with the car off and 12.3-12.5v with it running. I also tested where the positive cable meets the fuse boxes with the same results.
I'm just stumped to what the issue could be? a bad gauge? bad NEW alternator that tested good? or a bad battery even though its only a year old? I also have a hot wire kit for my fuel pump AND a very small system(10"sub with a 200watt amp) hooked up to the positive battery post at the fuse box but I've never had this issue before.
any help is appreciated.
On The Tree
Joined: Aug 2009
Posts: 183
Likes: 0
Junk that alternator & go buy a aftermarket one that has more amps. I have a similar problem. My stock one i had that came with the car worked fine. But when it went out i bought a new one from napa & when i get on it at wide open throttle the gauge drops to about 10 or 11 volts. & from what i can find researching on here... They are junk. So im gonna buy a high out put one. I read a thread today that people are putting the 145amp alternator out of a 2003 pickup to fix the problem.
The truck alternator is a popular swap but I personally didn't want to modify anything so I went to ws6store.com and picked up their Powermaster 150amp unit. Comparable price and excellent quality, I haven't had a problem since.
Last edited by arock24; Oct 31, 2013 at 03:31 PM.
On The Tree
Joined: Aug 2009
Posts: 183
Likes: 0
I would buy a aftermarket 145amp. The truck alternator you gotta make that top pig tail plug in longer. & you lose the back bracket for the alternator. & you might look into replacing your ground strap wire on the drivers side with a thicker ground wire. Just alil added security.
Thread Starter
TECH Apprentice
Joined: Sep 2011
Posts: 344
Likes: 1
From: La Porte, TX
I would buy a aftermarket 145amp. The truck alternator you gotta make that top pig tail plug in longer. & you lose the back bracket for the alternator. & you might look into replacing your ground strap wire on the drivers side with a thicker ground wire. Just alil added security.
You might want to check the exciter wire. It might be damaged. It sounds like you are having similar issues to what I was dealing with. The wire had pulled out of the back of the plug and it wouldn't charge.
Trending Topics
Thread Starter
TECH Apprentice
Joined: Sep 2011
Posts: 344
Likes: 1
From: La Porte, TX
That's what I was talking about, on the last alternator I pulled out I was in a hurry to get to the parts store before it closed and I accidentally ripped it out lol. But I replaced it with a new one.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Did you check the exciter wire when it's not charging? Did you check for a voltage drop at the big wire on the back of the alternator? Also see how many ohms you are getting from the negative post to the the block.
It sounds like something is breaking down after the car gets hot.
It sounds like something is breaking down after the car gets hot.
It should be pretty easy to diag this I would think. I get most of the obscure wiring issue at work.
FWIW this is how I go about diag for an alternator issue. This needs to be done when the problem is present.
Check all connections, battery terminals, distribution blocks, etc
Check battery voltage
Check for battery voltage on the big wire on the alternator, it should be the same as B+, if it's not there's excessive resistance in the wire from the battery to the alternator, this can be from corrosion, a broken wire or partially broken wire or bad connector.
Check for B+ on the exciter wire on the alt. If there is none check to see if you are getting B+ at the PCM connector. It will be the red connector at the PCM, pin 15, red wire.
Check the resistance on the ground side, start from the the negative post to the ground distribution block and several different places on the block. I fixed a heater blend door on a Taurus a couple months ago by cleaning the ground wire going to the block. I wouldn't have believed it myself if I didn't do it.
I hope this helps some.
J
I was thinking Exciter wire. I had the same problem. I ended up resoldering the wire and the stock alternator is good to go now.
I had picked up a Powerbastards Alternator, but all it did was squeal like *** from the load of trying to produce 220A.
I had picked up a Powerbastards Alternator, but all it did was squeal like *** from the load of trying to produce 220A.
Yes, the advice for the 140 amp truck alternator is good but you need to confirm what caused your problem.
Alternator went bad and the replacement from Orielly's was bad
OR
The exciter wire was bad and you got a replacement with the incorrect pin location
OR
There's an open in the wiring harness from the PCM to the exciter plug.
Alternator went bad and the replacement from Orielly's was bad
OR
The exciter wire was bad and you got a replacement with the incorrect pin location
OR
There's an open in the wiring harness from the PCM to the exciter plug.
Thread Starter
TECH Apprentice
Joined: Sep 2011
Posts: 344
Likes: 1
From: La Porte, TX
Thanks for all the help and replies, I just spliced it together for with a butt connector because I do not have a soldering iron. I'm guessing maybe the using the butt connector could be causing it to not work correctly(I don't understand why it would, maybe someone can clarify)? How exactly should I go about testing the excitor wire and the wire on the back of the alt? I have access to a multimeter and test light. Would I just uses the same 20v setting I used to check the battery?
Thread Starter
TECH Apprentice
Joined: Sep 2011
Posts: 344
Likes: 1
From: La Porte, TX
Thats what it seems like, the first few minutes of driving it charges just fine but a little bit later it slowly starts to dive off. I have also noticed the gauge has been quite erratic lately, for example, last friday on my way home I was at a red light and the gauge on the dash was reading around 10 volts then a few minutes later and it went back up out of the orange and went up to mayhemaybe 11.5-12ish volts
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
CHAD:
voltage drop test will quickly reveal high resistance across a connection or a ground;
for example, the voltage drop on the battery-engine ground cable should be less than 0.3V.