Jump to content
SAU Community

Alternator Problems

Mick

By Mick,
in General Maintenance

 Share

Recommended Posts

Mick Mentor

Mick

Posted
Posted

Hey my alternator was a standard 80amp for my r33 gtst s2 and it just wasnt charging the battery properly so i brought a second hand 90amp one from a r33 gtst s1 and it fit in ok and had the same size pulley so all good there, but i noticed a problem with it, on a cold start it will sit on about 10.5v and stay there while idling until i give it a rev and then it starts to work and goes to 13.8v, now im getting this reading from the Apexi RSM which is connected to the ECU and it must be what the car is seeing cos even the battery light comes on when it is idling and sitting on 10.5v but goes away after i rev it, but the funny thing is that when i put a multimeter on the battery or the relay box near the alternator it shows me a different reading of upto 1v difference. So does anyone know why there is upto a 1v difference from the battety to the ecu and why does the alternator only work after it gets a rev, i read something about an exciter wire but im not sure if thats for this altetnator

Link to comment
https://www.sau.com.au/forums/topic/451320-alternator-problems/
Share on other sites
blind_elk Grand Master

blind_elk

Posted
Posted

I had this same problem many years ago, although I had to rev to around 3k before the alternator would start charging. IIRC, it was a blown diode in the alternator. If you can, you should return the alternator as faulty. I'm not sure if the fault is repairable.

As for the voltage difference, you lose voltage through the wiring. The further from the source, the bigger the voltage loss.

Mick Mentor

Mick

Posted
  • Author
Posted

thankyou that sounds right about the diode, i had my original one apart a while ago to try fix and clean it and yeah i seen 4 big diodes in there so this one i got would have the diodes in it like my original one, im not sure if i should return it or open it up and put a new diode in cos im very good with electronics, would be an east fix for me to replace it and i would replace all 4 of them, i didnt make a note of the part number on the diodes when i had it apart but i assume they would have a part number on them and easily sourced, i also should try replace the 2 metal bushes i think they call them, the ones that are curved on the ends that are spring loaded and are located at the bottom of the rotor or stator or whatever the middle core is called again lol

G37Sam Collaborator

G37Sam

Posted
Posted
I have the same issue, problem is I bought (what was advertised) a rebuilt alternator with completely new internals and had it shipped all the way here. Is the blown diode easy to repair? Or should I just live with this?


I live in Dubai so shipping the alternator back to the US and having it replaced is not feasible.

Mick Mentor

Mick

Posted
  • Author
Posted

i can let you know how i opened my original one up when i seen the diodes that time but you will need a bit of electrical knowledge to be able to remove and solder in new ones, i think thats what i might end up doing with this one even tho i can return it cos they dont have another 90amp one there and if i repair this one i brought at least i know the diodes will be brand new, i think i took some photos when i opened it up if you want me to post them, it shows where the diodes are

jiffo Mentor

jiffo

Posted
Posted

I'd suggest it's a voltage reg problem rather than diodes, but I'd check brush length before digging too deep.

The brush lead limits extent of brush travel and once well worn, the brush won't make correct slip ring contact, it gets held back by the lead.

The fact it pumps out respectable voltage once you give it a rev. means it has the ability to generate OK, which it wouldn't do with inoperable diodes.

I've found with these old things, on engine start they don't charge, HICAS etc lights will flash as you move off.

Once you reach around 2000rpm the alternator will cut in and from then on she's perfect, charging at any rpm's.

Faulty regulator in those instances.

89CAL Grand Master

89CAL

Posted
Posted

I'd suggest it's a voltage reg problem rather than diodes, but I'd check brush length before digging too deep.

The brush lead limits extent of brush travel and once well worn, the brush won't make correct slip ring contact, it gets held back by the lead.

The fact it pumps out respectable voltage once you give it a rev. means it has the ability to generate OK, which it wouldn't do with inoperable diodes.

I've found with these old things, on engine start they don't charge, HICAS etc lights will flash as you move off.

Once you reach around 2000rpm the alternator will cut in and from then on she's perfect, charging at any rpm's.

Faulty regulator in those instances.

Agree with this. Pretty sound advice if you are willing to pull it apart to check those things

Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

Posted
Posted

Then there's another issue of them producing next to no current/voltage as rpm increases too.

I've had two stock RB ones do just that, as soon as the RPM increased past 4500rpm voltage drops dramatically and once you back off the accelerator the voltage went back to normal.

Ended up just buying an aftermarket 85amp bosch unit from a VL Commodore with the bosch to Hitachi harness. Works great now, however because it has an external fan it's makes this stupid whine noise which I don't like lol

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • Ben_D
      Wanted to buy R200 longnose LSD 3.9 ratio

      By Ben_D · Posted

      Hi all,  I am in the market for an R200 longnose diff out of a Z31 300ZX, or S12 RSX, DR30 skyline, or similar, in a 3.9 ratio.  Preferably a late model one with the M12 crownwheel bolts.  The only easy to find advert for one of these was my ad back in 2007 when I sold it on this forum.  I sold the diff as I had sold the car it goes to, but as it turns out, after 18 years I got the car back late last year, so now I'm looking for the diff !  If anyone knows where to find a longnose R200 LSD with the M12 crownwheel bolts, drop me a line at [email protected] - Bonus paid if soomeone comes up with the original diff (stranger things have happened !).  Cheers   Ben D    
    • Ben_D
      Back for more after 18 years - and where are the longnose R200 LSDs?

      By Ben_D · Posted

      Hi everyone, I used to post here a bit from 2004-2013, when I owned various Nissans, in particular my S12 RSX gazelle, which was sold in 2007.  As luck would have it, after an 18 year hiatus, the car found its way back to me last year, and over the past 11 months I have had the pleasure of restoring it with my kids.  One thing that I am after in particular is a 3.9 ratio R200 LSD for it.  I actually sold the one out of the car here back in 2007 , and it would be incredible if I could track down who I sold it to, so I can see how they have progressed over the years (and to be honest, to see whether I can get the diff back !).  Anyways, hi all and let me know "where are the R200 Longnose diffs all at these days ?  Cheers Ben D  
    • sonicii
      G35 Control arm and Compression Rods into a V35 Skyline.

      By sonicii · Posted

      Arms will be the same as the G35 or 350Z, but as above, there was a change in the lower control arm where it connects to the ball joint.  That said, you can remove the ball joint cone from your old ball joints and fit them to the new ball joints.  To be honest, I didn't think the ball joints themselves were different. The main ball joint is a bit awkward to replace, you really need to remove the steering knuckle to press out the old one.  Some people have used tools to remove it in place, but it just seemed too hard to get to. If you are going to press out/in that ball joint, then you may as well just replace the bushings in the LCA and the compression rod.  You can buy the compression rod bushing from Nissan, but the LCA bushes, you will need to go aftermarket. Much cheaper than buying the whole arm.
    • Erelyes
      Ceramic turbine damage to engine - what did yours do?

      By Erelyes · Posted

      Ha, well, it's been.... a bit of a journey. Things have taken much longer than I'd hoped. I'll probably put up a thread at some stage. Hopefully soon. The car's not done any kms since my update in June though, put it that way.
    • Dose Pipe Sutututu
      M35 Aftermarket Fuel Pump

      By Dose Pipe Sutututu · Posted

      Here's the chart for fuel pressure vs. current draw, assuming your base fuel pressure is 3 bar and you run like 0.5bar boost on WOT, you should only momentarily hit 9amps here and there. (Ignore my prev post, I cannot read a chart these days it seems)
×
×
  • Create New...