ok i am really having an issue with my Z28. bought the car had a used alternaotor in it and bad battery... replaced both with GM parts... drove it days later .......check battery light came on ... come to find out alternator gave out... i checked the L terminal with a DMM on volts.... there was a bad connection " wiggled the wire jumped from bat voltage to 0 " ... replaced the plug...the battery cable was sorta corroded.....swapped that one too ...swaped new alternator in drove it around for a day...punched the gas low bat light came on again !! i checked the wiring schematics it looks like theres a wire going to the PCM... i took off that plug and checked for continuity and that came out good... im guessing im going with a PCM this time .. has anybody on here had simular problems " yes i tried using search " but nobody seemed to have problems as bad as mine lol. oh and right after a new alternator the car works perfectly fine... i even put it on a VAT and it put out the correct amperage underload. i dunno guys gonna have it towed to the shop tomorow.

give me some ideas please.

1998 Z28 M6 white.

 

how does the ground cable look?

 

x2 I'd check that as well.

 

the ground cables off of the battery look ok no corrosion or anything the one going to the fender looks good. id imagine the other one goes to the block i cant really see right now in the driveway.. the problem however seemes to start and stays dead when floored or suddenly jerked. you know what i mean like if you drove around taking it easy on it it seems to work fine for awhile........but when you nail it at the light suddenly the check battery light comes and stays on. and the alterator has no output from there on out . where are the other grounds on the car ? i mean is it coincidence that this happend like 4 times lol. A bad ground would also make the car not want to start too though like it has a dead or weak battery too i believe right ?

 

How many times have you replaced the alternator? Maybe it's possible you got a bunk one from the parts store?

If you've replaced that again already then ignore this post... just a thought.

 

ok i got another new alt.. grounds are good all the basics are covered.. i put the car on the VAT and right away it was putting out 100 amps at idle....then it dropped to about 60 amps .. so its overcharging... looking at the wiring schematic. following the L terminal it goes to a 470 ohm resistance in the IPC.. .gonna have the IPC checked out.



The generator uses only two connections - battery positive and the L terminal, in addition to the ground path through the generator bracket. Use of P, I, and S terminals is optional. The P terminal is connected to the stator and may be connected externally to a tachometer or other devise. The I terminal can be connected directly to battery voltage to power the generator instead of, or in addition to,
"" the L terminal which must be stepped down.""
This S terminal may be connected to an external voltage source, such as voltage near the battery, for voltage control. If the S terminal in not used, internal generator voltage is used for control.

i think that would be the reason...the L terminal is not being stepped down from the resistor in the IPC... whats your guys thoughts .. i think im heading in the right direction atleast. lol

 

ok.... so i made a 470 ohm resistsance and bypassed the IPC still 100 amps at idle ...nothign same result... i tested the advanced auto battery and it tested good like 569 cca or something........i replaced it with a delco battery for ****s and giggles..." i work at a GM dealership " had one laying around... dropped to 30 amps and working properly.... ?!?!?!? somebody explain that one too me.. ohwell car is working now

 

My '00 SS was eating relays. After changing a number of them (cooling fans, ignition, fuel pump, etc), I noticed at start up the voltmeter went almost into the red for the first min of operation. Replaced the battery. Same. Changed the alternator to a new Bosch and the problem went away. Interseting, the new Bosch unit had a yellow information paper with it stating the voltage regulation unit was some different design from the GM original.