winsome

Dear all,

Recently the voltage seems to be very unstable as the rev increase, my radar detector has a voltage indicator and it goes up the roof to beyond 15.5 and when that happen the detector restart itself and once it cause the headlight to shut off. and the car vibrate a little during idle afterward. Could it be the battery is dying soon or something to do with the alternator?

Please advice and thanks

Winsome

kkim

Sounds like a bad voltage regulator, which I believe is in the alternator in the 993.

tj90

Thankfully, I have the radar detector voltage output and finding the same problem with my 993. Usually reads high voltage and causes idle problems as well as airbag light to flicker. If I stop the car and restart, many times the voltage will read between ~13-14 volts. When its misbehaving, I have seen readings 15-17 v.

Also, the battery is <1 year old and keep it on a battery tender between drives every week, so I dont think the battery is shot. I had the wiring harness replaced per recall a year ago as well.

Was anyone able to confirm that it was an alternator? If so, can I rebuild it or will I need new?

Thx. TJ

Felix

This needs to be fixed as soon as possible so that high voltages don't fry something, whether cheap like a radio or expensive like an ECU.

Whether to go new or rebuilt depends on what you can find. Nothing wrong with a rebuilt alternator if it's been done by a competent rebuilder and hopefully backed up with a warranty.

Adrienne

I'd suggest replacing the voltage regulator rather than the entire alternator. I replaced mine about 6 months ago, with the following symptoms: <1 y.o. battery boiling over at times, the air bag light coming on, odd CEL codes, and erratic voltage readings. Not all shops will know you can replace just the voltage regulator, but it's far cheaper and gets to the root of the cause. It's a pretty common problem from what I understand from my shop. No problems since I replaced it.

tj90

Is the voltage regulator part of the alternator? Where is it located? I saw that Pelican is listing a regulator ~$70 for 911 thru 1998. Mine is a 1995. Unfortunately, p-car.com does not have a DIY for voltage regulator. If the regulator is inside the alternator, I assume I follow the DIY on removing the alternator.

Thanks,
TJ90 - "soon to be rennlist member soon since this site has saved me so much money!!!"

Dr. P

Do not drive your car if voltage is reading higher than usual!! replace the voltage regulator and you'll be fine, no need for a new alternator 99% of the time.

Adrienne

Yes, it's part of the alternator, and your price from Pelican sounds about right.

Dr. P

If these cars have Bosch alternator then any VR made for Bosch alt. will work. Even your FLAPS should have one for ~$15-20. Pull your old one and bring with you just to make sure. My $.02

Lorenfb

"I'd suggest replacing the voltage regulator rather than the entire alternator." - Adrienne -

Not a good idea because:

1. The rotor slip rings are usually worn to a point requiring turning or replacing
2. The bearings become "dry" at the mileage when the alt. fails.
3. The labor cost/time to R/R the alt is such that a complete alt. replacement is
most cost effective for the long term.

Note: Avoid cheap/junk regulators which may be problematic causing future failures
the result of the very high heat seen by the 993 alt.

tj90

OK - I wanted to give everyone an update. I removed the alternator and found that one of the wires (brown) slipped right out of the electrical connector that was still bolted to the back of the alternator. As described on p-car.com, there are 3 wires - a big red one, small blue one and medium brown wire. Its hard to tell if the brown wire was pulled during my removal process or if it was loose from the wiring harness recall done a year ago. Perhaps the porsche tech did not see that the connector was loose.

My question for the alternator guys out there is this - if the brown wire was loose could it have caused the high voltage reading. The problem showed up on the way to work and of course on the drive home tonight the voltage was ~13v where it needed to be. It was a definitely intermittent.

I will search Autozone tomorrow for a replacement BOSCH regulator. Now that I have the old one in hand, I will know what to look for...

JasonAndreas

The part number for the voltage regulator is #928-603-142-00 and the part number for a rebuilt (comes with a two-year warranty) by Porsche alternator is #964-603-156-AX.

Lorenfb

"My question for the alternator guys out there is this - if the brown wire was loose could it have caused the high voltage reading." - tj90 -

The brown wire is an additional ground wire besides the alt. case ground.
This ground wire would not cause the problem described.

ZombiePorsche44

If it was my car, I'd do the alternator as well as the voltage regulator, why wait to do it later when you're already in there?

More often than not, people try to do things the cheap/inexpensive way and end up paying more in the long run.

It's a Porsche, don't be a penny pincher or you'll be sorry.....................ZP44

Adrienne

It's not a matter of penny pinching; it's a matter of fixing what's broken. You would no more replace the alternator if the alt. belt broke...