Leland Pate

It's getting pretty cold here in Montana. I usually go out to the garage to warm up the car for ten to fifteen minutes before I leave.

So, when I go out to climb in it's already been running for a few minutes. WHen I turn the lights on, I can hear a low, steady "Whirring" noise emminating from the alternator. I guess the current draw is causing a load on the alternator and I suspect the cold weather is increasing the resistance in the headlight/running light circuit causing the alternator to make this noise under increased load.

That is my guess. Now... what should I do about it. Is this a signal of imminent death of an alternator? Should I be concerned?

Lorenfb

"I guess the current draw is causing a load on the alternator and I suspect the cold weather is increasing the resistance in the headlight/running light circuit causing the alternator to make this noise under increased load."

Your 1st statement is correct about the increased load. The resistance of the copper
wire does change with temp, but it's is so small that it has NO effect. The resistance
of the lights determines the alternator load.

As long as the alt. is charging properly, it's O.K. and probably not going fail in the
short term. The 964/993 Bosch alternators are very reliable. The will fail beginning
at about 80K+ miles because of worn slips rings and regulator brushes. They will
fail prematurely, as will most/all alt.s, when the battery is jumped backwards.
Also, a common problem on 94/993 alternator is over tighten belts which can
snap the long alt. shafts and/or damage the bearings.

BS911

I had a very similar experience. At idle speeds with an alternator load, I got the whirring sound. It turned out to be a very loose... probably ready to bust belt. I replaced the belt and all was fine. You might even be able to see the belt whobbling around on the pulleys causing the whirring sound.

... or it could be entirely different.

Glen

Turn off the lights....Sorry could not resist... Autozone will sell You a alternator with a lifetime wty for Your car at a VERy reasonable price if it needs one. I think they were 175-200$ last time I bought one. Hope You get it sorted!

Leland Pate

Thanks for the reply, fellas.
It doesn't sound like belt noise, but I'll check the belts tonight anyway.

I'll probably drive it until something goes Kaput.

There is another sort of strange noise I continually hear while driving. Sure sounds like a turbocharger spooling up coming from behind my head. It sounds an aweful lot like radio/alt. interference but it makes the "turbo" noise with the radio on or off.

I can't complain... sounds kind of cool...
Enjoy your weekend, gents!
If I can get my hands on that Hazet tool, I'm yankin' out my suspension to install some H&R springs. Whoo HOO!

Adrienne

Hey, as luck would have it (?), my alternator belt broke yesterday! So, word to the wise, don't wait until something goes Kaput. Because mine went Kaput, the shop has no belt until Monday, and I ended up getting stranded on the highway when my battery lost too much charge.

Mdrury

Sounds identical to symptoms I've experienced => impending belt failure. There's also a pulley set upgrade that's recommended for 95/96 models. Anyone know how important this is?

Lorenfb

"Turn off the lights....Sorry could not resist... Autozone will sell You a alternator with a lifetime wty for Your car at a VERy reasonable price if it needs one. I think they were 175-200$ last time I bought one. Hope You get it sorted!"

Just what you want to put in your Porsche, an Autozone part. How good is that
warranty when the part fails on a long drive in the middle of nowhere?

PLEASE!

Randy M '96 Silver 993

Mine is going the same thing. All belts are fairly new (Under 20K) and I have the pulley update. The noise seems to be coming from the top of the engine.

Everytime it starts making the noise, it is late and the shop is not open. I just don't want to take it in when the noise is not happening and waste everyone's time.

Let us know if you find anything.

Glen

Loren, I guess a rebuilt Bosch part will not be good enough for You then. I have used them for years and since I have had 3 964's and 7 993's and have built 3 race cars off those platforms, done my own Twin Turbo conversion(at my house) and currently race a SuperCup I may have some semblance of knowledge in this area.... I have also used the Autozone brake pads for years with the lifetime warranty and am very pleased with those also. 27$ and 47$ per axle for pads with lifetime wty for 964 and 993's has been just great for me. The PN 's on the pads are MKD 547 for Big Red Fronts, MKD 447 for Big Red rears or 993 regular fronts. MKD 446 for 993 rear and 964 C2 and c4 all the way around. Another helpful bit we found was that the Denso AC compressor is also available at a several hundred $ discount through Autozone. If You want the AC comp even cheaper You can retain Your bracketry and buy the compressor for a Nissan Maxima(identical compressor) install Your brackets and You are on Your way. This thread is worth 2k to those of You who DIY on these issues alone, perhaps more.
Hope this helps!

Robert Linton

Glen:

For a very large amount of money, I could sell him a 140 amp, 7 pound racing alternator -- but he doesn't need it.

Bob

DarrylH

(With apologies to "Pretty Woman") - Are we talking a very large amount, or an obscene amount? Everybody needs one!

Robert Linton

Obscene! $2000!! But it's used by Porsche Racing, LeMans Winners, NASCAR teams, World Rally, etc.!!! And saving 7 pounds of high and rear weight "ain't bad"!!!!

Glen

Bob,
That's great! Thanks I needed that. That is an awesome piece, I remember when you told me about it, must have been almost 2 years ago! BTW please let me know if You are ever in SuperTaco territory and we will sync up.

DarrylH

Dunno how many "normal" Porsche parts prices you've been exposed to lately, but $2k for an exceptional alternator looks almost reasonable! I'd be the first to admit that maybe I've completely lost perspective, though.