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...

[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?