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

    • Dose Pipe Sutututu
      Borg Warner EFR Series Turbo's V 2.0

      By Dose Pipe Sutututu · Posted

      This is the other log file, if only we had exhaust manifold pressure - would understand what's going on a bit better   Can you take a screenshot of your wastegate setup in the Kebabtech?   Engine Functions --> Boost Control (looks like this):  
    • GTSBoy
      Mistakes were made, my R34 Story

      By GTSBoy · Posted

      You just need a datalogger of some sort. A handheld oscilloscope could do it, because it will make the trace visible on screen, so you can look at the peak, or whatever you need to look at. And there are cheap USB voltage loggers available too. You could get a 2 channel one and press a button to feed voltage to the second channel at points that you want to check the sensor voltage, when you knew what the guage was saying, for example.
    • Dose Pipe Sutututu
      Borg Warner EFR Series Turbo's V 2.0

      By Dose Pipe Sutututu · Posted

      it's not the issue with making power, it's the issue with controlling boost, and this isn't the first time I've seen a 6Boost having issue with controlling boost down low.   The boost control here looks interesting.   Looking at your logs, looks like it's set to open loop boost control strategy (which is fine). We can see VCT being kept on till about 6600RPM (no issue with that). Ignition timing (I'm assuming this is E85, seems within reason too, nothing too low, causing hot EGTS and boost spiking). There's about 15 degrees of advance when your boost shoots up, however can't be this as the timing isn't single digits. I'm assuming there's no EMAP data, as I wasn't able to find it in the logs. We can see your tuner sets the WG DC to 0% after 4300RPM, trying to control boost.   My thoughts, what frequency is your wastegate set to?  AND why aren't you using both ports for better control?
    • GTSBoy
      Borg Warner EFR Series Turbo's V 2.0

      By GTSBoy · Posted

      While that sounds reasonable, this is definitely a boost control problem, but the real question is why are you having the boost control problem? Which is why I pondered the idea that there's a problem at ~4000rpm related to head flow. In that instance, you are not yet under boost control - it's still ramping up and the wastegate is yet to gain authority. So, I'm thinking that if the wastegate is not yet open enough to execute control, but the compressor has somehow managed ot make a lot of flow, and the intake side of the head doesn't flow as well as the exhaust side (more on that later), then presto, high MAP (read that as boost overshoot). I have a number of further thoughts. I use butterfly valves in industrial applications ALL THE TIME. They have a very non-linear flow curve. That is to say that there is a linear-ish region in the middle of their opening range, where a 1% change in opening will cause a reasonably similar change in flow rate, from one place to another. So, maybe between 30% open and 60% open, that 1% change in opening gives you a similar 2% change in flow. (That 2% is pulled out of my bum, and is 2% of the maximum flow capacity of the valve, not 2% of the flow that happens to be going through the valve at that moment). That means that at 30% open, a 1% change in opening will give you a larger relative flow increase (relative to the flow going through the valve right then) compared to the same increment in opening giving you the same increment in flow in outright flow units. But at 60% opening, that extra 2% of max flow is relatively less than 1/2 the increase at 30% opening. Does that make sense? It doesn't matter if it doesn't because it's not the main point anyway. Below and above the linear-ish range in the middle, the opening-flow curve becomes quite...curved. Here's a typical butterfy valve flow curve. Note that there is a very low slope at the bottom end, quite steep linear-ish slope in the middle, then it rolls off to a low slope at the top. This curve shows the "gain" that you get from a butterfly valve as a function of opening%. Note the massive spike in the curve at 30%. That's the point I was making above that could be hard to understand. So here's the point I'm trying to make. I don't know if a butterfly valve is actually a good candiate for a wastegate. A poppet valve of some sort has a very linear flow curve as a function of opening %. It can't be anyelse but linear. It moves linearly and the flow area increases linearly with opening %. I can't find a useful enough CV curve for a poppet valve that you could compare against the one I showed for the butterfly, but you can pretty much imagine that it will not have that lazy, slow increase in flow as it comes off the seat. It will start flowing straight away and increase flow very noticeably with every increase in opening%. So, in your application, you're coming up onto boost, the wastegate is closed. Boost ramps up quite quickly, because that's really what we want, and all of a sudden it is approaching target boost and the thing needs to open. So it starts opening, and ... bugger all flow. And it opens some more, and bugger all more flow. And all the while time is passing, boost is overshooting further, and then finally the WG opens to the point where the curve starts to slope upwards and it gains authority amd the overshoot is brought under control and goes away, but now the bloody thing is too open and it has to go back the other way and that's hy you get that bathtub curve in your boost plot. My position here is that the straight gate is perhaps not teh good idea it looks like. It might work fine in some cases, and it might struggle in others. Now, back to the head flow. I worry that the pissy little NA Neo inlet ports, coupled with the not-very-aggressive Neo turbo cam, mean that the inlet side is simply not matched to the slightly ported exhaust side coupled with somewhat longer duration cam. And that is not even beginning to address the possibility that the overlap/relative timing of those two mismatched cams might make that all the worse at around 4000rpm, and not be quite so bad at high rpm. I would be dropping in at least a 260 cam in the inlet, if not larger, see what happens. I'd also be thinking very hard about pulling the straight gate off, banging a normal gate on there and letting it vent to the wild, just as an experiment.
    • Borci88
      Borg Warner EFR Series Turbo's V 2.0

      By Borci88 · Posted

      Not a problem at all Lithium, I appreciate your help regardless. I've pulled a small part of a log where the target pressure was 28psi and it spiked to 36.4psi. I've only just begun using Data Log Viewer so if I'm sending this in the wrong format let me know.
×
×
  • Create New...