t3HW41ru5

Hey All!

I posted here a while back about trying to decide whether or not to buy a 1981 911 SC. Thanks to the advice here, I did go ahead and purchase it, but as a second car, which was the best decision I feel.

Regardless, the car is now mine, including any and all headaches that come with it. So far, the car has been a blast and not that big of a drain on my wallet. I ended up putting in a new stereo, and the fuel pump was failing, so I replaced that myself as well.

However, I've run into an issue that I cannot seem to figure out. For a long time, I was getting a really nasty smell in the car. I assumed it was burning oil, or something similar, but the smell was too acidic for that. I eventually discovered it was the Battery, and that the system is overcharging.

When I put a volt-meter on the battery, and rev the motor, the system shows the voltage rising in sequence with revs. I was seeing as high as 18 Volts, which is definitely not good. At idle, I see 14 Volts, and with engine off, I see 12 Volts. With engine off, and all electrics on (lights, etc), I see 13.88 Volts.

I replaced the voltage regulator, thinking that would probably fix the issue, but I got the same problem with the replacement regulator. Now, the replacement regulator I bought was used, but it was from the same year/model of car, and was tested and I was told that it was working. There is a chance that the regulator could be DOA, but I do not know at this point.

Not sure what to do at this point. I scheduled a spot at a shop, but I figured I would try here first just to see if anyone has had this problem before.

Thanks in advance!
-Chris

wwest

There is a possibility that the VR you replaced was NOT in use. Some PO may have replaced the OEM alternator with one having an internal VR. On the other hand a partially failed, failing alternator has been known to cause battery overcharging.

theiceman

My Thought exactly before i even read this,. First Verify which Alternator you have , one with an internal or external Regulator.

Early cars can be upgraded to an internal Regulator Unit. Not that I am an expert by Any means but i have never head of a Regulator go bad and cause this on an Externally Regulated car. But have heard this consistently on internally regulated cars. So Check this first.

If it is I the original woring and external regulator ai would check the wiring very carefully.

. I would think if The external regulator was in the circuit you could unplug it and have zero charging ( just read bttery voltage ) , although I am not 100% on that, just may be an easy way to see if the Regulator is in the circuit.

Also means you will be flushing your battery tray with a baking saoda/water solution . batery Acid in that area will eat that fast.

t3HW41ru5

Hey Everyone!

Sorry for the long delay in posting back. Finally found a soultion to this.

Turns out the previous owner DID replace the Alternator, which means it was upgraded to the newer style alternator with the INTERNAL voltage regulator, and that INTERNAL regulator had failed.

Ended up replacing the Alternator and now everything is good! Thanks for the help everyone!

theiceman

Good news. Another happy motorist up.and running

mpiffaretti

Old Thread, but I am having overcharging issues myself. I have the OEM alternator with an external Voltage regulator. I want to change the alternator to the upgraded one with Internal regulator. My Question is , is there any new wiring that I have to do? What do I do with the external regulator cables?
thanks!

theiceman

there are a few thread an d article on the net. Someone here has the Porsche service bulletin as I have seen it . I am sure someone will post it. if not here on pelican.