Once the new one kicks in will it maintain the voltage? Answering this question will tell you if it's the old alternator or not.

But, I wouldn't expect the voltage to drop significantly let alone go below 12V while "making a pull".

From the voltages I measured on my car, I expect you could fix it by connecting a 100 ohm, 5 watt resistor between switched ignition power and the L terminal on the alternator. This will give it the extra current required to energize it at idle when the engine starts.

You are tuned or can tune it so get the alternator monitoring turned off in the PCM. System settings uncheck the L and F terminal. Then you can add whatever alternator you want. Then, put a light or resistor between switched ignition power and the L terminal of whatever high powered alternator you install and you're good to go.

 

thanks bud, this is exactly what i was looking for. i haven't tried driving with the new alternator, never bothered.
my car is no where near stock and im thinking im just drawing to much load for the stock 110 to handle.

i have aftermarket spal fans, larger external fuel pump, plus the intank pump, meth pump, 2 "small" amps for the stereo, shift light and the list goes on, i just think its to much for the alternator. it would also explain to me why it only does it "during a pull" since thats when the external fuel pump and meth pump kicks on.

im thinking of going with a BT 170 at this point instead of messing with this. do what you said or just run the pigtail and have it shut off in tune like you stated.
i just brought my oem alternator to auto zone to get tested. it passed but they said it sounded like the bearings are on there way out. also the replacement one from autozone didn't work... go figure.

one question i have tho is if i do replace it with a larger unit and use the pigtail/resistor. i know it will still throw the charge system fault but can i just clear that on the dic before driving? or will it actually do something with the car like limp mode or something? im only asking because im not able to get my car to my tuner till some time next month and im wondering if i need to wait till then to swap alts or i can just do it now and live with the code for a bit.

 

You can clear the fault. It won't affect the car except for being annoying due to it insisting on being on the DIC over riding other messages.

If the F or PWM terminal isn't connected to the PCM or gives the wrong PWM duty cycle range then it will keep coming back.

I'd first simply plug-in the BT alternator and see what happens. It just might work for you. But, if it throws a code then first try the resistor between switched battery power and the L terminal with the PCM still connected and see if that fixes it.

Extra pumps kicking in could explain your voltage drop. I'd still double check the wiring. Easy way is to put a volt meter with one lead on the alternator output stud and the other on the battery terminal. You should read a low voltage, like < 0.25V or so maximum.

 

it reads .2 from stud to terminal. stud ground reads 14.8 and battery reads 14.8 at both terminals.

considering how sensitive the car is with non oem units im sure it will not work with just plugging in the BT unit lol but who knows, could get that 1 in a million shot.

 

Don't know how helpful it will be but it's interesting to read... maybe Neutron82 will jump in he put in a 170 BT and apparently has NO issues

https://www.corvetteforum.com/forums...ernator-3.html

 

Chalk me up as another CF member with a C5 alternator that put out "variable voltages". I didn't get the CEL - I got the DIC message on charging system.

After reading the previous threads - I brought my old alternator in to a local electrical shop to be checked - they checked it the next day and said the regulator / diodes were gone. They quoted me over $200 to rebuild it (even after telling me the bearings eat were perfect). I ended up buying a new alternator from a Chevy Dealer that does a significant amount of on-line sales. It was somewhat more expensive than the rebuild, but it worked, and the problem was solved...

So - if you do enough internet searching - you'll find a place or two that sells a Valeo regulator that supposedly fits our alternators.

www.aspwholesale.com

My question is has anybody actually done a Valeo alternator voltage regulator R&R themselves and if so - is it relatively easy - or is it beyond the scope of most of us "do-it-to-yourselfers" ???

 

Take a look at this post. It answers your question and has info on the right regulators for both, 97-01 and 02-04. The price is around $30.

 

is that the part that is causing the issues with the replacement alternators and why we need to rebuild our originals?

ive taken my own alternator apart before and that part is pretty easy to remove/install. (took it apart to paint)

 

Yes

 

That is awesome info thank you

 

GCG - THANK YOU !!! Excellent info !!! I still have my old alternator - so I'll get the regulator for it, and that should pretty much guarantee I won't have charging problems in the future.

 

so could someone purchased a reman and just swap that part from ebay? just curious for future.
im ordering a BT unit.

 

If it's just the regulator what's bad, replacing it should be all you need, but if the diodes are gone they would require replacing as well. It would be a good idea to get a second opinion on the diodes, or check them yourself