The fix for my endless alternator failure's
05-31-2010, 03:55 PM
#1
The fix for my endless alternator failures I posted a thread a while back about having alternator after alternator fail, one literally lasted about 5 minutes. These were all new or rebuilt and I tried new and rebuilt from 4 different suppliers. I went through 10 alternators before I gave up on off the shelf alternators.
Long story short I tested every thing multiple times and even replaced the exciter wire and connector, never could find an issue and it all started when I replaced the factory original alternator with an aftermarket one, and it was all downhill from there.
The fix.... A truck alternator. I got the idea from another board member that the truck alternator actually fits the F body cars, so I went to the junk yard and spent $40 on a used 2003 Truck 145 amp alternator bolted it in and the voltage has never been more stable.
The 145 amp truck alternator only has one simple modification that needs to be made to use it, it does not use the rear support bracket that the F body alternator does so remove the one bolt and bracket, other than that it bolts directly in, plugs directly up, and works good!! So for less money you can have an higher amperage output, more stable, more durable alternator if you go this route. The pulley was even the same, this couldn't be easier.
I hope this helps anyone else with the same issues, here is the link to my original thread if you feel like reading more details of the problems I was having
https://ls1tech.com/forums/generatio...ders-here.html
Identifying the right alternator: Get a 2003-2004 Truck alternator (may even apply to up to around 2005?), 145 amp, 4 pin connector, the code junk yards use to identify it is "KG3". The standard truck alternator is a 105, but some trucks with a lot of electronics use the 145. When I ordered mine I told them it was a 2003 truck, 145 amp and I got the right one. Also you can tell them it's a "KG3" code alternator, that's some code the scrap yards use apparenlty for that alternator. I got mine from LKQ for $43.30 picked up.
Some more info on identifying the alternator
ALSO VERY IMPORTANT Replace the alternator connector, the single wire connector with the plastic plug in on the top, these fail and cause problems as well. Here is some information on the connector.
AC Delco part PN# PT1136 (Oreilly has another brand also for the connector, don't remember the name brand)
I got mine from NAPA so you can try going there or go to Oreilly. They are all over Ebay too, search LS1 alternator connector.
EDIT 6/2018 some are saying it's getting harder to find 4 pin truck alternators in the junk yards and as time goes on it's gonna get harder to find them. So you can go to a 2 pin and do the conversion or try a new AC Delco. I would imagine those are just fine, when I had all my problems back 7 years ago I didn't have an AC Delco alternator available in a price I could afford, I believe they were $300-$400 for the F body fitment at the time and I couldn't risk spending that much on an alternator and possibly burning it up and getting the run around about warranty, so I went with a used to test my theory. And it just so happened that alternator never died so I left it. I made this thread so that people could have a low cost fix for a problem many of us were having. And I've advised people to skip the new alternators because so many had excellent luck with the junkyard OEM alternators, but they will be gone soon. I will still advise to avoid the off the shelf Autozone and Oreilly alternators (or whoever, I went through several from Oreilly, autozone, NAPA etc when this all was going on) and go with an AC Delco unit.
Long story short I tested every thing multiple times and even replaced the exciter wire and connector, never could find an issue and it all started when I replaced the factory original alternator with an aftermarket one, and it was all downhill from there.
The fix.... A truck alternator. I got the idea from another board member that the truck alternator actually fits the F body cars, so I went to the junk yard and spent $40 on a used 2003 Truck 145 amp alternator bolted it in and the voltage has never been more stable.
The 145 amp truck alternator only has one simple modification that needs to be made to use it, it does not use the rear support bracket that the F body alternator does so remove the one bolt and bracket, other than that it bolts directly in, plugs directly up, and works good!! So for less money you can have an higher amperage output, more stable, more durable alternator if you go this route. The pulley was even the same, this couldn't be easier.
I hope this helps anyone else with the same issues, here is the link to my original thread if you feel like reading more details of the problems I was having
https://ls1tech.com/forums/generatio...ders-here.html
Identifying the right alternator: Get a 2003-2004 Truck alternator (may even apply to up to around 2005?), 145 amp, 4 pin connector, the code junk yards use to identify it is "KG3". The standard truck alternator is a 105, but some trucks with a lot of electronics use the 145. When I ordered mine I told them it was a 2003 truck, 145 amp and I got the right one. Also you can tell them it's a "KG3" code alternator, that's some code the scrap yards use apparenlty for that alternator. I got mine from LKQ for $43.30 picked up.
Some more info on identifying the alternator
ALSO VERY IMPORTANT Replace the alternator connector, the single wire connector with the plastic plug in on the top, these fail and cause problems as well. Here is some information on the connector.
AC Delco part PN# PT1136 (Oreilly has another brand also for the connector, don't remember the name brand)
I got mine from NAPA so you can try going there or go to Oreilly. They are all over Ebay too, search LS1 alternator connector.
EDIT 6/2018 some are saying it's getting harder to find 4 pin truck alternators in the junk yards and as time goes on it's gonna get harder to find them. So you can go to a 2 pin and do the conversion or try a new AC Delco. I would imagine those are just fine, when I had all my problems back 7 years ago I didn't have an AC Delco alternator available in a price I could afford, I believe they were $300-$400 for the F body fitment at the time and I couldn't risk spending that much on an alternator and possibly burning it up and getting the run around about warranty, so I went with a used to test my theory. And it just so happened that alternator never died so I left it. I made this thread so that people could have a low cost fix for a problem many of us were having. And I've advised people to skip the new alternators because so many had excellent luck with the junkyard OEM alternators, but they will be gone soon. I will still advise to avoid the off the shelf Autozone and Oreilly alternators (or whoever, I went through several from Oreilly, autozone, NAPA etc when this all was going on) and go with an AC Delco unit.
Last edited by 00pooterSS; 07-02-2018 at 12:04 PM.
05-31-2010, 04:43 PM
#3
I dont have pics but may be able to take some in a bit when I get home...
And im glad you posted up, I had given up hope until you gave me the idea to do this so I wanted to thank you for ending that nightmare!! I may still go that route you suggested but for right now this is working great.
I thought I would have to move the sway bar or fans since the stock one is hard enough to get around those things but I was still able to work this big honking thing through and into the hole. I was amazed at how easy it was and how well it worked.
All my rebuilds would go below 13 volts within about 20-30 minutes ESPECIALLY if I was running the system, and they would either way with the a/c on and it was hot sitting at idle. I have gone on 3, 100 mile or more trips in the past 2 weeks with a/c, headlights, system, everything on all the way and its steady right at 13...
Last edited by 00pooterSS; 11-28-2011 at 09:17 PM.
05-31-2010, 06:50 PM
#5
Not once its bolted up, one of the lines looked like it was going to touch the terminal for the battery cable, but once it was mounted there was room between the two, I went ahead and bent it away just a hair anyway.
Ill get you some pics in a min
Ill get you some pics in a min
05-31-2010, 07:05 PM
#6
The 200 amp alternator I installed a couple of years ago was in a truck case...removing the rear brace wasn't a big problem for me since I hated getting to that bolt anyways when messing with it, and the terminal on the back is also easier to access with the truck case vs. the stock one.
Glad you found a solution...problems like these can drive you up the wall.
Glad you found a solution...problems like these can drive you up the wall.
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06-01-2010, 02:11 AM
#10
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I was going to get the alternator from the link but I got a CME valance and tips instead, so I wont be able to get that anytime soon 
but I can most likely afford one from a junk yard. Does anyone know if I can use any v8 truck alternator and from what years?
but I can most likely afford one from a junk yard. Does anyone know if I can use any v8 truck alternator and from what years?
06-01-2010, 11:13 AM
#11
The 200 amp alternator I installed a couple of years ago was in a truck case...removing the rear brace wasn't a big problem for me since I hated getting to that bolt anyways when messing with it, and the terminal on the back is also easier to access with the truck case vs. the stock one.
Glad you found a solution...problems like these can drive you up the wall.
Glad you found a solution...problems like these can drive you up the wall.
No problem, I like to help when I can to repay all I have learned myself here on LS1tech
The stock one goes straight down into the alternator and the truck one the plug goes in slightly off to the side which means the wire has to be just a smidge longer, but I would assume there is enough free play in the length of the stock one.
If you call the junkyard they can cross reference the years. So just say 2003 truck 145 amp 4 wire plug in and you should get what you need.
And like I said even the pulley was the same so it was easy as could be
Last edited by 00pooterSS; 06-05-2010 at 07:22 PM.
06-01-2010, 11:15 AM
#12
^^^ have the same question
and, stock alternators have a bolt on the back? what do you meant you didnt have to put a bolt on the back?
because i have the same problem as you but mine when i took off what i think was the stock alternator never had a bolt on the back?
and, stock alternators have a bolt on the back? what do you meant you didnt have to put a bolt on the back?
because i have the same problem as you but mine when i took off what i think was the stock alternator never had a bolt on the back?
06-01-2010, 12:04 PM
#14
I would not recommend changing the stock one unless you have a problem with it, they are a much better product than the aftermarket ones. There may be a good aftermarket one if its custom built, but these off the shelf parts store one's are crap!
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fucter (02-07-2021)
06-03-2010, 02:22 PM
#17
And if you've gone this long without it obviously you have been ok so yeah I would say its fine.
06-03-2010, 09:04 PM
#20
Have you noticed any better gas mileage? I swear I read a thread a long time ago where a board member got some high output alternator from ebay and he claimed that he found another 1-3 mpg... or something like that. As I recall others jumped on board saying that they'd also seen better MPGs out of bigger alternator. I hope this doesn't sound like a stupid hydrogen-injection flux-capacitor type of question, lol.
