Alternator issue - SR20det

[NIZLAH]

Chaps, I have a problem with my alternator on my sr20det - it went on me around 6 or so months ago so I chucked another used one in which has been fine up until the last few days, Saturday I noticed my car was a little weak when it started, but I drove around and didn't experience any problems.
Didn't drive it Sunday or Monday, went to start it this morning and it had nothing, juice was empty, so chucked the charger on it while at work, got home cranked it over and I wasn't getting any charge from it (multimeter)
Then I gave it a rev and the alternator kicked into life and seemed to be working well (reading 14.9-15.2volts)

No loose connections, or loose belts etc, so the only thing that I can think of is the regulator, which apparently suck on these alternators.....

anyone else got any other ideas or test methods for me to look into ???

Cheers
Niz

[pt_y2k]

14.9 to 15.2 volts seems to high...From memory you have a 2 pin plug on the alt ,should be "S" and "L"...make sure you have the "S" terminal with a decent 12v supply,as close to the positive battery terminal as possible,if you have a voltage drop it can cause the alt to over compensate.

[NIZLAH]

yeah I questioned if it was a little higher than it should be, would this over compensating cause it to fail over time? pretty sure all connections are good and they are nice and close to the battery (within 400mm)

[matt99]

Internal voltage regulator sounds hammered?

[pt_y2k]

Ya it certainly could cause it..:) Just have a peep at what symbols are on the alt ,it could also be IG and L and maybe you have IG powered constantly? That would mean the reg is never switching off nd could cause failure...To be honest i rebuilt alts for years and very rarely saw them Hitachi give trouble...

[NIZLAH]

hmm, cool, well it was a used alt of unknown condition, so who knows how much life it had left in it.... cheers for the input gentlemen

[Golberg]

I wouldn't say 15.2v is insane. I wouldn't immediately blame the alternator if that's the reading.

Do you have a charge light connected in your cluster. Your symptoms of no charge until pushing the revs up are textbook no charge light hooked up (or bulb blown). What most people don't realise is that you need the light hooked up in order to start the alternator charging. It can come on of its own accord if the RPM gets high enough though.

[NIZLAH]

yeah yep found this out before when re-doing my dash cluster (its all custom, original cluster is long gone) I changed the charge light to an led but found it doesn't pull enough current to light the alternator's fire, so swapped it for a normal bulb.... funny thing is, it operates like normal when reds are turned on and starting etc, but doesn't show when the alt isn't charging??

Also, obviously its been charging for the past 6-8 months...


I wouldn't say 15.2v is insane. I wouldn't immediately blame the alternator if that's the reading.

Do you have a charge light connected in your cluster. Your symptoms of no charge until pushing the revs up are textbook no charge light hooked up (or bulb blown). What most people don't realise is that you need the light hooked up in order to start the alternator charging. It can come on of its own accord if the RPM gets high enough though.

[NIZLAH]

so Ive just done the bastard job of changing the alt out with another used one (that apparently worked) and its not charging at all, I asume this alt is another dud, but is there anything else that I should be looking at for testing/trouble shooting??

[pt_y2k]

You need to check your 2 pin plug. Have a peep on the alt for a pinout. It's either S and L or Ig and L. If S ya should have battery voltage with key off at this pin, if Ig when key on... Is your charge lamp working with the new alt?

[NIZLAH]

ok cool I will check the pin outs on the plugs, but I don't understand why it has worked fine previously and its a stock harness so should be wired right, I will check none the less though.
Charge light only ever works on start up, doesn't come on any other time regardless...

[pt_y2k]

How do you mean start up? Ignition on or only while cranking?

[NIZLAH]

comes on when ignition is on, illuminates for a second or 2 after starting the car, usual scenario

[pt_y2k]

Ah ya cool! Where bouts are ya? I can take a look if your still stuck if I'm passing some evening.

[NIZLAH]

just went and had a play with it with a test light, only the b post would give power, tested the other main plug terminals with the car on and off and couldn't get anything, this was with the plug off though as I can't probe them while its on obviously.

Also found a 10 amp fuse in the box next to my battery that was blown, replaced it and it would pop as soon as ignition was turned on.... even tried a 20 amp in it to no avail.
trying to work out what fuse it is as there are no schematics on the lid, and I'm not sure if its a factory fuse box or was added when the conversion was done. (motor is not in a nissan chassis) so still trying to work this one out, google isn't really giving me much at the moment

[pt_y2k]

There's your problem so, can ya see what the pin layouts are on the alt or have you a part number and il check? Il give ya a call if I finish up near you some evening mate.

[NIZLAH]

yeah can see the pin outs, S & L I think it was... much appreciated mate.

[pt_y2k]

To do a quick test ya can just run a wire from the b+ lead on the alt to that s wire and see if it charges, I bet it will...:)

[NIZLAH]

so your saying (just so I don't arch myself out or anything surprising lol) to run constant 12v either from the b post or directly from the battery to the s terminal (obviously with the plug off yeah) and leave the remaining terminal with nothing connected - correct?

[pt_y2k]

Yup exactly, just splice into into the s wire with the plug still connected and put a small fuse on the piece of wire you use if ya wanna be safe too...:)

[NIZLAH]

sweet I'll give it a crack and report back in a day or 2..

[NIZLAH]

got around to doing some tests, the S terminal (bigger white wire) is getting 12v, the signal wire/dash light doesn't seem to be getting any power but I only tested with the keys on, not running and was done with the plug disconnected.
I'm not sure what is supposed to going on in that regard...?

Also the fuse that keeps blowing gets the same voltage reading as the battery, so its obviously connected, but doesn't seem to affect the running of the car when its not there.

I'm thinking its just another busted alt, since the faggot who sold it to me won't reply to me, even when he said he has another he'd give me if it doesn't work...

Any other ideas before I go to the hassle of pulling it out again and replacing it?

Any techniques to bench test an alternator/its components??

[pt_y2k]

If your using a bulb circuit tester it should light the tester dimly on the "L"pin with igniton on...or alternatively you should get a low voltage reading on it...how many alts have ya now? is it a bitch to pull out? i could open them and have a look but testing is limited unless ya can spin them, if ya want and if i finish in the workshop tomorrow you could run what alts ya have up to me in Capalaba and i could pop them open and tell ya whats what in them...:)

[NIZLAH]

I was using both test light and volt meter, didn't get a reading from either... I've got 3, one still on the car, real #### to take out but will prob do it over the weekend...

I was thinking if I put the alt's in my vice and rigged up my drill to spin them if there was anything I could test?
Can you offer a rebuild on one of them for a reasonable cost? (or do you do something else for a crust now days?) might go down that path if its not too exy

[pt_y2k]

And you say the charge light is working on yeah? thats strange,amybe your missing something tho. Am I dunno,could give it a go maybe with a mains dril to get the rpm up...you'd want 6 or 700 at very minimum to excite the alt id say? To be honest i havent touched an alternator or starter in nearly 2 years...but we do have accounts with ashdowns so if parts are available i could no issues...Ya need to make sure its not wiring first tho i guess..!

[NIZLAH]

yeah charge light is working, I honestly don't think it's the wiring as its been running for the past 2 years without hassle, just had the one dead alt about 8 months ago and now its failed/playing up as well...
If you don't mind, can you look into the availability of the parts to do a full rebuild on one and get back to me via pm with a price to do so if your willing.... I'm tossing up the decision to buy a new/rebuilt alt on ebay for $200 but if I can get it done cheaper I'd be keen, need to get the beast back on the street asap, hate only having one car to rely on ...

[NIZLAH]

well to update my situation, I have just sourced another 2nd hander alt, chucked it in and after a quick blip of the throttle it kicked into life, still charging at 14.9 - 15.2 volts but it seems like its working...... I guess this is just normal for sr alternators?

[NIZLAH]

so after a day or 2 of driving Ive noticed that cranking is weak (as if the battery is half flat) once it kicks and is given a rev the alt brings everything up to speed and it runs fine... (this was why I thought the alternator was fucked in the first place) The battery is not too old, less than 2 years, its a sealed Aldeco unit, so shouldn't be stuffed.
My only thoughts are that maybe the higher voltage the alt is/was putting out has buggered the battery over the last year or 2?
I did read a disclaimer on the battery saying maximum charge voltage is 13.2V which I thought was a bit odd for an automotive battery...

any thoughts?

[NIZLAH]

no one feel like chiming in?

[ahstwin]

Have you tried doing a parasitic draw test? Let's say for argument's sake that the alternator isn't the problem and you're having a current draw coming from another component and the alternator is struggling to keep up with keeping the battery charged.

[NIZLAH]

Have you tried doing a parasitic draw test? Let's say for argument's sake that the alternator isn't the problem and you're having a current draw coming from another component and the alternator is struggling to keep up with keeping the battery charged.

I can't say I have, but its crossed my mind, but even after driving for a while and turning it off and re starting soon after it still feels like the battery has jack all charge, can't think of anything that would suck the juice out of it so quick and also it would be dead flat after a day or 2 if it was draining it so fast.... I had this problem when I bought the car, it used to drain the battery over a day a day or 2, was a an easy fix as a relay was just wired wrong....

Whats the best way to test if a battery is shot without actually replacing it?

[ahstwin]

You could bring it down to your local mechanic and ask them to test the battery for you. They use this really nifty tester which you can buy yourself for about 500 mate. Provides a cca reading and voltage too. A parasitic draw test would be good for isolating the problem to one component if at any that is.

[NIZLAH]

sweet, cheers for your input mate..

[ahstwin]

No worries. Keep us posted on how it goes.

[NIZLAH]

ok fairly sure Ive got to the bottom of the issue, took the pig down to battery world today to see if they would replace my battery under warranty, not quite as it needed to be sent to the supplier for testing, but he did give me a good battery to use in the meantime which was appreciated.

Testing it there showed the alt charging at nearly 15v (already knew this) so I'm fairly certain the previous alt I had in there was also charging high like this and has fucked the battery, so Ive changed the alt thinking it was the problem (still kind of is) but it was the battery all along, but obviously due to the alt charging at too high a voltage......

Will see how my luck goes with warranty claim..... ......

Anyone know if sr alts often have issues with the regulators? seeing as the one that I just threw in is doing the same as the old one......

[ahstwin]

I've never had a problem with SR20 alternators. CA18 however, I've had one come up with a current draw which sucked the life out of the battery overnight. I do have a dead SR20 alternator in my workshop though. Gonna pull it apart sometime and diagnose the problem. When I get down to it, I'll let you know how it goes.