rjla67

So I have a issue that I cannot seem to correct where at WOT I am seeing a voltage drop above 4000RPMs which will cause the lights to dim and just before red line, the check gauges light will come on. It will return to normal if the accelerator is released. Cruising around the problem will not surface at all. So here's what's been done so far:

• Brand new GM alternator (lifetime warranty)
• New power steering pump
• 1yr old GM water pump
• New GM belt tensioner
• New GM belt & new Gatorback belt

I have another alternator coming to swap out to see if that is the problem for I've never seen this issue before so that is what I *hope* the issue is. I'll also be replacing the battery just to make sure but I can't see what that would cause the issue. Only other thing I was thinking was belt slippage but other then the crank, every pulley is clean and brand new including the belt so that kinda rules that out.

The car is slightly modded with the usual bolt-ons and was tuned and I don't have much in the way of electronics to draw lots of power.

Is there anything else I should be looking at while I got the car up and replacing the alternator like grounds or such anyone can think of?

b4cz2896

I had the same issue with multiple "re manufactured" alternators. I finally fixed it by buying a used one from a junk yard.

rjla67

Wow, never would of guessed a junkyard one would be better then one remaned. I've seen lots of threads here on the subject but not one really solves the issue that I can see.

Belt slippage is the most common response but I know that it isn't the issue. It's gotta be the brush springs since it only happens at high rpm's.

studderin

iTrader: (28)

UD balancer?

gagliano7

My junkyard gave me a lifetime guarantee on my truck 130 amp alternator . Alternator cost $80 from junkyard.

99Bluz28

iTrader: (35)

OD alternator pulley would be more likely to cause higher rpm alternator issues(over revving), but his issue sounds like it's just a bad(new) alternator.

rjla67

New alt going in tomorrow so hopefully that is what the issue is.

I also replaced the idler pulley today while I got it apart for it looked scorched and it didn't freely rotate so the bearing must be going out and is binding.

Strangely when I want to the parts store the one listed for my year was completely wrong (and $58). The inside of the pulley facing outwards was straight whereas it needs to be at an angle going down for the dust shield to sit correctly. Had to lookup one for a 2000 Corvette and it works perfectly (and only $20).

silversrtman

iTrader: (20)

I had a similar problem a couple years back. I went through 3 alternators and the buick tensioner pulley trying to find the problem. Turns out a katech tensioner was the answer. Idk if this is your problem but couldnt hurt to try, plus the katech piece is really nice looking and its about the same price as an oem tensioner. Good luck.

rjla67

Swapped out the alternator and it performs as it should so it must of been a bad rebuild.

Just a precaution I also replaced:

Battery
Battery terminals
Idler pulley
Tensioner pulley
Belt
PS pump
Tightened up all the grounds
New spark plug wires
Removed the exciter wire from the plastic wrap so it wasn't as tight and has a little more slack

Might of gone a little overboard but didn't want to take a chance.

rjla67

Well took it out again to test and it's doing it again. This time, the voltage won't come back up so I am at a total loss...

bmax

iTrader: (1)

Maybe take a peek at this.

https://ls1tech.com/forums/generatio...-failures.html


Good luck

rjla67

Well, went through the entire system again. The brand new GM alt burned out after only one WOT test run and was not charging the battery. Everything else checked good so as it turns out threw in a rebuilt alt that has better internals and so far she's holding steady as it should.

Majestic9C1

iTrader: (19)

stick a 145A truck alternator on...

why GM decided to use a 102A alternator on these cars is mind boggling

rjla67

I agree. Even with just basic bolt-ons and the stock stereo, these alts GM uses just can't handle the load and crap out at high rpm's. Driving around normally the problem never surfaces but who does that?

If it happens again I'll just have it locally rebuilt with high-output internals and be done with it.

BubaGumpShrimp

iTrader: (1)

Just a quick note, make sure your power steering lines are not leaking. A lot of people have issues with leaking pumps/lines and the alt is right under it.. I had this issue along with 3 alt swaps till the high pressure line fully showed its leak and drained the tank right into the alt taking it out...

rjla67

Already replaced that so it's good there. It was leaking a little so I replaced it to rule that out.

Footlead

iTrader: (18)

Put one off a truck or suburban, yukon on it. read the link above. I did and it works great. I had my original rebuilt and the same thing. lights dim on WOT The alternator is a bad design. Youtube videos confirm it.

NVUSZ28

iTrader: (5)

I hope you have fixed the issue, but check this out, it fixed my voltage drop at WOT.

http://www.calspeedperformance.com/p...cei-102130.htm