GTA91

iTrader: (14)

I'm running a '98 LS1 in my '91 GTA. The '98 alternator just has a 1 wire hookup and after much research it was determined that I just needed to apply 12v switched power to that terminal on the alternator with a 470ohm resistor inline. It works and charges now, but sometimes while driving the voltage will drop down to about 11.5 volts or so. It may stay there for a long time (minutes) or maybe only for a few seconds and then come back up to 13-14 volts. Anyone have any ideas as to what is causing this?? How does everyone else have their alternators wired up and anyone having issues like this? Thanks for ANY help!!

-Jeremy

1dirtyZ

iTrader: (1)

could it be tha fan kicking in and scking too much amps/ volts?
just a thought.

GTA91

iTrader: (14)

Never though about that but I don't think so. Sometimes the voltage will drop down when I get on the throttle too. I wonder if the alternator is junk?? It was a brand new one but it came from autozone.

ahowudoin

iTrader: (2)

sounds like a crap alt.

GTA91

iTrader: (14)

Well I drove it about 50 miles last night and about 130 or so today (road trip) and it did it last night but not today... weird.

crewchef

iTrader: (6)

Jeremy, sorry to hijack but this alternator thing is something I haven't quite figured out yet. I've got the 98 LS1, PCM and wiring harness. There is a single wire running from the PCM to the alternator connector. Is this the wire you're using to the alternator or are you just running switched power from another source? If I use the existing wire do I still need to put a resistor in-line? I've read a bunch of posts on this topic but just getting more confused.

GTA91

iTrader: (14)

From what I've read, the '98s only had a 1-wire setup and the PCM wasn't involved at all. '99-'02s had the PCM supplying the lower voltage required (7-9volts or something). In '98 they didn't use the PCM and instead used the dash light or a resistor to drop the voltage from 12 to 7-9 or whatever. Basically after '98 they (GM) got smarter and just had the PCM supply the required lower voltage. Just forget that wire in the harness and ditch it. Then just supply switched 12volt power to that terminal on the alternator with a 470ohm resistor inline. It should work just fine, just don't apply the full 12volts to to the alternator... you'll fry it... just ask me, I fried 2 alternators before we figured it all out.


later- Jeremy