here's the problem,

I'm having trouble with my charging system, the problem is intermitant and has no rhyme or reason.

at times, while sitting at idle (550 rpm) my head lights and fog lights dim way down as does the amp gauge(almost into the red), as soon as I speed up the motor everything brightens up and does fine. other times it does just fine at the same rpm with all the same equip. running. I would think that if it was due to the alt. not turning fast enough (too large a pulley) it would happen all the time, I would also think if the alt. was not big enough (it's a 94 amp. reman.) that it would only do it while the heavy load stuff is on (lights and fogs,rear defrost), not so, it will also do it during the day with nothing on except the radio.

I have already checked all my connections and grounds, all seem fine, the alt and the battery are only about a year old. the pulley on there now is 2.5 inch dia. and the smallest one march pulleys has is 1 11/16, would a half inch make a big difference ?? belt is tight and new

 

You said it only happens sometimes, right? Do you have any heavy loads running, like a big stereo or whatever? Can you still have the problem when the stereo is set at a low volume?

There's always the possibility that something's wrong inside the alternator. Next time it happens, try giving the alternator a light blow with a hammer or tire iron.....it things suddenly improve, that's where your problem is..... but recheck all the connections there before you go get a new one.

 

It sounds like it is the alternator. That's kinda what mine did right before it went. It would charge just fine some times, and then not charge at all. It would do this back and forth, until it went all together. Go to Auto Zone or any auto store, and they should check it for free. You might try an alternator that puts out the recommended amps(105 for my camaro) as well, especially if you're running a sound system, fog lights, etc.

 

two words
voltage regulator
hehe
good luck

 

On a GM car, the voltage regulator is built into the alternator....theoretically, you could disassemble the alternator and just replace the regulator........ but in practice, you would want to rebuild the entire alternator, or buy a rebuilt one or used one.

 

ditto

 

There could be a relay that kicks on and the alt is spinning slow enough at idle that it could cause a big current draw, like the fuel pump. Just a thought. If it was a bad voltage regulator then I wouldn't think that the system would charge at all. I know it's a different system, but when the regulator on my T-bird went out the system wouldn't charge at all. It was old enought that it had an external regulator and was easy enough to replace.

 

If you have the all in one headlight modulator that was my problem. The modulator was shorting inside causing voltage problems and erratic headlight operation. New one from E-bay fixed it. Only after eliminating all the other variables you mentioned. Good Luck!!

 

You don't have underdrive pullies do you, that can cause the alt to spin below the alt. minimum operating rpm at idle.

 

okay i'd say voltage regulator is the problem, it is an electronic component that can test good and in reality be bad or it can also go back and forth being good then bad ect. seen it several times, i'd say buy a GM alternator and put it on, or buy and aftermarket lifetime warranty one but those usually lock up after about 6 months, i finally stepped up and bought a GM from work because i was tired of putting alternators on, this was the fifth when i put it on lol anyway i'd say replace it, its easier, also check negative ground wire at block just in case

 

figured it out, it seems the 10si 85 amp alt. I had was not sufficient enough to carry my load at low rpms, I switched to a 17si 105 amp and the problem is gone.

thanks for all the help !!!