Have a 92 s10 with a 5.3 Ls swap and I recently been having trouble with alternators failing. I went through 3 already and I can't seem to figure out why. The wiring isnt wired differently from the s10 chassis and I haven't ran into this problem before. The swap was completed about 2 months ago and it ran perfectly fine! Just stumped.... Anyone got any suggestions??

 

how do you have the alternator wired? is it being ECM controlled?

 

Its a 2 wire hook up. I don't think its pcm controlled. Both wires from the clip go to the firewall where to the s10 harness. The first alternator gave me a sign it was going out by having a draw in voltage like an accessory was kicking on. That wasn't the case seeing as the dual spal electric fans are turned on by a toggle switch. They have a relay on each fan too. The trans cooler fan however does not. I don't see that being a significant draw on the power since thats the only real hardwired component. The second alternator would fluctuate from 19 volts to 10 and then nothing. The third just died. The last 2 worked perfect after replacing and then would act stupid til they failed. I didn't have any other problems before the first alternator died and that makes me a little hesitant to dig into my wiring because of that.

 

There should be a wire from the PCM that excites the alternator. Does yours have a 4-wire plug?? On my setup (2001 LS1) with a 2001 PCM there is single wire going to a 4 wire plug. There is no resistor needed if it is coming direct from PCM because it has it built in internally.
The 2nd wire from top is the one I have hooked to the PCM. I had it reversed and messed up my previous alternator.

If your not using PCM to excite the alternator you need a resistor. See this thread. https://ls1tech.com/forums/conversio...e-voltage.html

 

Its a 4 wire clip but the pcm was programmed to enable the single wire hookup. I'm guessing it deleted the control of the alternator from the pcm? There were other mods done to the pcm to allow for stand alone operation. I'm just confused to why it would be failing. I read somewhere that I might have faulty parts from the autoparts store. I didn't go with ac delco cause duralast was the cheapest I could afford and now I'm wondering if that was a mistake.

 

Ok so I think I'm understanding how to install a resistor to the alternator wire. Hopefully this works but Im wondering which kind of resistor to go with. I'm gonna go with the resistor type that is shown in the link above and see how that works but its a different alternator. Mine is off of an 04 suburban 5.3 and the link has it from a 99 f-body. Would I need to buy a different type of resistor?

 

Wasn't there a recent thread on this topic??

 

I don't think you read my post or looked at my picture at all. I have a 4 wire clip like you do, and only ONE wire is even hooked up to it. See my picture in the post above. It goes direct to the PCM. You need to look it up on the pinout for your particular computer.

Please re-read my post.

 

... And just for giggles, here is a pic for use in a car without PCM control (like a carb car)

 

^^^^^^this too

 

Easy killer, I must have just skimmed through your post and misunderstood. I went straight to the link you provided and figured out what yall were talking about with the resistor. I installed it and so far is seems to be working for now but that's after going through 4 shitty duralast alternators from AutoZone. The reason I doubted the resistor was because the alternator they gave me tested good on the bench at the store but suddenly failed on my truck. I finally got a good alternator after assertively telling the clerk their parts were ****. Like I said everything is going good so far. I have it setup like a carb style alternator cause the pcm was programmed that way. He did it to allow single wire setup. I have 2 wires still coming from the 4 wore plug but one goes to ignition power and the other goes to the dummy light.