993,951,944

My C4S now has 72K miles.
The original alternator is still functioning; but is
there a "general rule" for alternator life expectancy ?

This is an important question to address as a
failed alternator will result in a stranded motorist.
This is especially not fun for a P-car owner.

This is also a broad question that parallels a common
physics question: "How long is a piece of string ?"
Many factors vary the alternator life expectancy:
Belt tension will determine bearing life; RPM and
electronic loads will determine internal diode and
brush contact life. Production defects can also
be a factor. After-market high power stereo amplifiers
and poor battery charge maintenance, as well as excessive
battery age, will also theoretically shorten alternator life.

Has anyone experienced a premature alternator failure
and at what mileage ?

Has anyone eclipsed 100K miles on an original alternator ?

Hopefully, we can collect some data to establish a general
mileage rule for alternator replacement

manek

For what it's worth, mine lasted 75k miles. about 2k miles after I bought it... <g>

Tito

Mine went at about 84K miles, shortly followed by the battery.
The wiring harness was done under warranty just prior to this.
The wire connecing the battery to the starter motor has just gone (96K) - my car is currently waiting for the part to arrive from Germany at Porsche Retail Hatfield.

Shame the Bosch bits aren't up to the same durability as the Porsche bits (ie engine).

Tito.

9elheven

993,951,944-

I just experienced a roadside failure at 57,600 miles. I was not happy.

Terry Adams

Past 100K and still on the original.

kdurg

52k on the car...no problems. Battery was replaced as consideration when I bought the car at 42k.

Good Post !!

4n6 MD

The alternator on my '96 993 cab. also died about three months after I purchased the vehicle. At the time of failure, I think I had ~20K miles on the vehicle. As I recall, the cost to replace the unit at the dealer was about $1000.

JohnM

Good advice, but re "nothing else that can go": the bearings can fail, I've seen a couple of posts from owners who have had this happen, in rare cases the alternator siezes and the belt then shreds . How one predicts an impending failure of that sort I don't know.

Randall G.

My factory 964 engine had 100k miles, original alternator, when the rod bearing spun. That alternator went away when I installed the 993 engine.

993,951,944

In view of the replies, it looks like some
of our alternators can reach 100K miles.

With some of the lower mile failures,
it's difficult to determine if the failure was a
self destruct of the alternator or an electrical
short, or aftermarket overload, causing a heavy
load on the +12 volt line.
A weak battery can also pull-down and overload
the alternator as well as improper jump starting
techniques. We now have some idea of
alternator life, but more data is needed to be
more definitive.

Caution and preventive maintainance, such as
frequent battery replacement, maintaining battery
charge while in storage, and avoiding installation
of aftermarket electronics that place high current
demands on the alternator, will extend alternator
life.

JChiles

77K miles, it died on me last week..

viperbob

I've seen them die with 40K miles, and I have seen cars with 120K+ with the original still working fine. I'd say that that on the bell curve, 2 std. deviations from the mean would be 65-85K...

Terry Adams

Mine is still the original at 135K.

Edward

Mine went at 90K-somthing. But like the chicken/egg conundrum, the demise of my alternator coincided with the death of the battery ...so which went first will be forever a mystery

Edward

epj993

Mine is original at 51K.

Just curious, I would think the alternator would work fine up to its rated capacity, so does load really make a difference? Isn't the alternator output constant with excess power basically running out to ground?

I'm not an electrical guy, just trying to better understand.