racehorse

Friends,

Help.

I have an 81 sc and need help. A little context.
My battery light comes on and stays on when car is off. Voltmeter says 12 volts.

So, I figure alternator is bad. I have it rebuilt and reinstall it. Light stays on. Voltmeter still reads 12 volts. I take out alternator, have it checked at shop. It's charging at 12 volts then jumps to 16-17 when asked. I put it back in. Light is on when car is running. It turns off when car is off.

I change the voltage regulator. Voila. Light stays off. But, still no charge from the alternator. Battery reads 12 volts.

I did put in an aftermarket (generic) regulator from my local porsche parts place. When I was last driving the car, (apparently on battery alone) it pulled strong then petered, the tach bounced around and then died.

I don't know what to do. A fellow 911 friend said to try another volt reg. Then, if that doesn't work, I'm thinking about testing each wire leading to the alt.

Help.

Mike

Face15

Mike,
You may want to get a cigarette lighter type lead (Radio Shack) and test the voltage with it hooked up to your DVM as you drive around. It does sound like a voltage regulator problem from your most recent report. Pelican Parts has replacement regulators for ~$56, I wouldn't skimp when it comes to this part with a generic brand.
Anyway, drive around with the voltmeter hooked in to the system and see what you get. Looking for around 14V with nothing but the engine running, and then you should get a drop, but not lower than about 12.8 with everything on (defrost, A/C, brights). If you see any spikes above 15V, definetly the regulator. Since it sounds like your alt tested fine on the bench, I'd guess your VR is erratic/about to go/ or already toast. I had a similar problem recently, so I feel your pain. (VR bad)
Hope you track it down.

racehorse

Todd,

Thanks for advice. The volt reg seems the consensus from folks I've chatted with. I'll try your idea about driving around w/DVM wired up. I wouldn't have thought to do that.

Thanks again. Much appreciated.

Mike

TC_SJ

I have similar problem with charging light went off & on sometime. while dring the car sometime the seat belt warning line turn on and also the charging light turn on, espcially when driving at night, if iether one or both of this light turn on, the head light got brighter. some one has told me that my VR has a bad block of diode and need to be replace. Since I have not drive the car much so I never bother to get it done. I did hook up the Volt meter thru cigarette lighter socket and alway got 14V and above, with defroster crank up and AC on, still do not see voltage drop or increase

TC

BoyT-911

Mike,
I known people who had similar problems with the alternator. Replacement is not cheap, so they rebuilt them, replaced defective voltage regular or even the diode. But they don't last long and the problem keeps coming back.

Finally, my mechanic suggested that I replace the old and temperemental alternator with the new alternator with integrated regulator. Since it was replaced in 1995, I never had any problem and probably the best upgrade with the greatest gratification I had for the car. If you decide to get a new alternator, I suggest you consider getting one with integrated voltage reulator.
Just my two-cents.....

Bill Gregory

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva"><strong>Finally, my mechanic suggested that I replace the old and temperemental alternator with the new alternator with integrated regulator.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">I did this on my SC. The factory technical bulletin on how to do this is in the Porsche "Parts and Technical Reference Catalog, 911 models 1974-1989". (Which every 74-89 Porsche owner should have, best $10 bucks you'll spend). Note the procedure calls for buying a new rear hub for the updated alternator, and these have been NLA from Porsche for years. You don't need to buy a new one, just cut out a small part of your existing alternator hub to accomodate the embedded voltage regulator. A file or dremmel tool works fine, as you're removing maybe 1/2"-3/4" of plastic material.

racehorse

Thanks to all. A fellow 911 owner here, who has the integrated volt reg. on his sc offered up his old volt reg for me to try.

salud,
Mike

TC_SJ

Hello Bill:

I am about to attemp to replace the Voltage Reg on my 87, since the charging light keep came on.Could you please tell me where to find the info you wrote below.

Thanks
TC
--------------------------------------
I did this on my SC. The factory technical bulletin on how to do this is in the Porsche "Parts and Technical Reference Catalog, 911 models 1974-1989". (Which every 74-89 Porsche owner should have, best $10 bucks you'll spend). Note the procedure calls for buying a new rear hub for the updated alternator, and these have been NLA from Porsche for years. You don't need to buy a new one, just cut out a small part of your existing alternator hub to accomodate the embedded voltage regulator. A file or dremmel tool works fine, as you're removing maybe 1/2"-3/4" of plastic material.

Face15

TC_SJ,
Your volt regulator in the internal type, attached to the back of your alternator. In order to replace it, you need to pull the fan and housing out, and then replace the VR. There is an excellent article by Wil Ferch on the Pelican Parts website, under Tech Articles. Take a look there, I just did the same a few months back...
The Tech Reference Catalog Bill describes involved changing an external VR to an internal one - not needed with your year.
Cheers,

BoyT-911

TC_SJ,
Face15 is correct about your alternator. The alternator with integrated VR was used by Porsche starting 1982 on 911 models. This and many more information are available in 'Parts and Technical Reference Catalog' for 911 models 1974-1989 (December 1995 issue).