lavoy

iTrader: (2)

Hi guys after searching for a few hours today i am still as stumped as i was before i started searching, any way here is the issue i have a ls1 swap in a 71 datsun, the motor and computer are from a 98 or 99 F body, the problem is i never get much charging from the alternator, i am used to seeing 14+ from any charging system and this one sees 13.5 at best and soon as the motor is warmed up and the fans and lights are on its more like 12.9-13.0. this concerns me since i am boosted and the more voltage the less chance of a misfire. the battery is new, the wires are all new and of proper size, the swap was done by 417 motorsports and its all top notch. the single red wire to the pcm is fine as well. the alternator is a reman unit and about 6 months old. i thought that maybe the electric fan and twin fuel pumps and lights ect might be to much draw for the alternator but after learning more about it i see that many camaros are running the same parts with no issues. the voltage at the battery, gauge and fuse box are all exactly the same so its definitely the amount of voltage the alternator is producing. so here is what i wonder, since the pcm is in control of the charging can i tell it to charge more threw hp tuners? does any one make a higher out put alt that is the exact same external dimensions? i cannot use any other external size alt my turbo set up just barely clears now. what other ideas and options are there? i just want more then 12.9-13.0 at all times. what i think is happening is the pcm is thinking its ok to turn down the charging after the cars warmed up, is there any way to take the pcm out of the loop so i charge full blast at all times? i saw that the older ls1 alternators use a resistor and a second 12volt wire. but the style i have "must" be connected to the pcm to work. sigh.. im stumped.

Goldcuffs

Just take it off and have it tested at the zone or your local parts store. That way it will rule out PCM or wiring.

lavoy

iTrader: (2)

most those places are idiots and that aside it seems to only do it once warm so how would i duplicate that on a test bench?

MTN_Z

iTrader: (7)

I have a reman from autozone and they tested it and it checked out fine. I was having charging issues at the time and found out the exciter wire was damaged. I replaced the wire and it charged fine but it was weak like you were saying. I think the remans just aren't very strong because when it's hot and I have the a/c running, cooling fans running, and radio on, the charge goes down to 12.9-13.0. There are upgraded alternator recommendations in the general maintenance forum you might want to check that out. I definitely need to do this also.

Pwebbz28

iTrader: (31)

Mine used to pulse alot and voltage dropped when the fans would come on. I had it rebuilt to a 160amp and its awesome!!

NINO_SS

iTrader: (7)

idler pulleys helps too check them out and replace them, that did the trick for me

CamdLS1'00SS

iTrader: (12)

agree with the tensioner pulley, i dont trust reman parts on hi-po toys, being myself id toss the 160 amp or bigger alternator on and bite the brand new cost

S10xGN

iTrader: (11)

Same here. Is this arbitrarily a "problem" or does it just bother you? It never bothered me until now. Now this thread makes me unsure if I'm charging correctly (although the battery is always up)...

lavoy

iTrader: (2)

I called around and all the local parts stores say they only show one option, where do i purchase a higher out put model?

MTN_Z

iTrader: (7)

I never remembered it dropping that low with the stock alternator, so when I see it below the halfway point on the voltmeter it just seems a little abnormal. I'm sure it's fine, but I would like to upgrade the alternator eventually.

01 ss vert

iTrader: (1)

Powermaster Alternator is what I went with a few months ago. Been great ever since!

f-bodyguy

iTrader: (9)

i got a 160 amp from local o'rileys(thats all they had in stock at the time) now somethings acting up hoping its a wire

blubyu02

iTrader: (17)

check out the power bastards on ws6store website

lavoy

iTrader: (2)

ok a little update . called two local alternator repair shops, told them what was going on, both said to move the pin over to the second in from the right and run switched 12 volts to it and report back, so i did voltage went up to 14.2 cold and dropped to 13.1-13.2 hot the one shop offered to test it for free if i brought it in so i did and it passed every stress test with perfect results and the wave pattern was perfect it was holding a steady 110 amps and peaked at 130. so i was back to square one, they suggested i look over the wires again so i decided to run another heavy wire from the alternator to the battery and a new trigger wire into the dash to a 12 volt switched source, after doing this the voltage went up to 14.5 cold and drops to 13.6 hot so im still getting a drop but i can live with 13.6 , just wish i knew what was making it drop after a while when it dont do it on the test bench. any way i figured that i would report in what i found, for those of you who want to run a ls1 alt with no pcm all you do is run 12 volts to the second pin in from the right as you look at the back of the alt with the pulley facing away both shops assured me this is perfectly fine to do. oh and they also told me that the 98 style and 99 style ls1 alternators are actually the same regulator part number.

bigred122

I was having a fluctuating voltmeter bouncing between 13 and 14 volts, and so I replaced the battery thinking it was on its way out. The problem didn't get any better with a new battery, so I started thinking about the alternator.

After reading some of the posts about the exciter wire, I pulled off the top connector tonight to inspect the excitor wire and connection, and plugged it back in, and now my problem is gone. The wire wasn't broken, but I think it just had a bad/dirty connection, and just unplugging it and plugging it back in was enough to make a more solid electrical connection on the pin. So I think I have fingered the problem. Thanks for pointing me in this direction, you saved me buying a new alternator.

bigred122

I was having a fluctuating voltmeter bouncing between 13 and 14 volts, and so I replaced the battery thinking it was on its way out. The problem didn't get any better with a new battery, so I started thinking about the alternator.

After reading some of the posts about the exciter wire, I pulled off the top connector tonight to inspect the excitor wire and connection, and plugged it back in, and now my problem is gone. The wire wasn't broken, but I think it just had a bad/dirty connection, and just unplugging it and plugging it back in was enough to make a more solid electrical connection on the pin. So I think I have fingered the problem. Thanks for pointing me in this direction, you saved me buying a new alternator.