Ciamaichelo

Over the past two months, I have experienced several dead batteries in my 2005 911 Carrera S (3.8L 997 manual). My battery is less than a year old and it passed two separate test at Kraigen and Autozone. After charging the battery, it will discharge after 4-5 days of driving to about 60%. At that time, the car will struggle to start and eventually fail to start. The battery test OK with a voltage of 12.6. With the car running and high beams, fan and radio on, the battery pulls insufficient voltage to charge or pass the alternator test, using a $15 alternator testing tool, my battery charger or the alternator test at Autozone.

I changed the alternator with a new OEM Bosch alternator and charged the battery to 100%. Thinking I solved the problem, I drove for a week and again the car was slow to start and next time failed to start, requiring a boost.

I then installed a new battery, thinking the bad alternator and frequent discharging killed my old battery. I then tested the new alternator and battery at home and at Autozone. Again, with the car running the battery still pulls insufficient voltage to charge the battery and the alternator tools also state low voltage output. I assume the voltage regulator is part of the new alternator and I disconnected and charged the battery prior to installing the new alternator.

What other components could cause insufficient charging voltage from the alternator to the battery? I read on 6Speed that a bad alternator cable could be the cause. Is there a fuse somewhere? or burn out cable? Any ideas or help would be greatly appreciated.

Thanks,
Chris

boolala

Seems like many of us who have early 997s have the same problem to one extent or another. Just before taking my car in for winter service I read on RL of a problem with excessive voltage drop across the alternator cable (> 0.5 V) that someone was having. After taking my car in for brake flush, oil change and new winter tires my indy said I needed a new alternator ($1100) because there was only 12 V at the battery. I told him about the cable problem and, after retesting, was surprised to find adaquate alternator voltage but significant voltage drop acorss the cable. The quote to replace the cable was $700, almost all labor. I took a pass on this as my batteries have lasted about 3 years (in spite of 10 K milage per year) which is a little less than I would have expected.

So, instead I bought a CTEK battery maintainer (again after reading a recent thread about it here on RL). After a month or so, I hooked up the CTEK (via the cigarette lighter adapter) and it "topped off" the battery. It took about 24 hours of charging. I think that I will simply connect the CTEK for one day each month and hopefully that will lengthen the battery life. In addition to the harsh cold midwest winters, the battery is stressed by the many frequent short trips that I make.

I think that this likely will not work for you because your battery is discharging so rapidly. Someone who recently changed out the alternator cable stated that the insulation was "melted." (He had replaced the battery several times over a period of a few months). Clearly there is a spectrum of issues here from a mildly reduced battery life to a possible fire hazard.

In any case check the voltage at the alternator and then, again, at the battery. There should be no more than a 0.5 V drop.

McCulla

Do a search on this as there has been a ton of discussion on this issue. I, too, have an 05. There are 2 known issues that stand out if the alternator and battery are good. As stated in the second post, the alternator cable and current drop over it's length are one biggie. The second one is the wiring harness to the starter. Both a dealer and a good indie will know about these. I believe that I read recently here that there are TSB's regarding both of these problems, but I can't confirm this. I recently took my car to my (EXCELLENT!) independent shop and they were actually able to confirm that both of these 2 wiring fixes have already been done on my car (I checked out of paranoia). Take your car in and tell them of these 2 problem areas and they should be able to test/check them to determine if they are the source(s) of your "current" issue. Good Luck!

Ciamaichelo

Thank you for both excellent replys. When refering to replacing the alternator cable, are you speaking of the fat stiff cable that bolts to the back of the alternator or the thin 2-wire green cable that plugs into the alternator?

Is it likely possible for a non-mechanic to change this cable at home or is there a ton of dismanteling to get to the cable? Also do you know where the cable is melting?... I believe I read it was near the starter. If so, would I only need to replace that portion of the cable.

Thanks again,
Chris

Minok

If the battery is good and the alternator itself is good, the other component of the system is the wires between the alternator and the battery and the car. If the wires don't allow for proper transfer of power, due to very corroded ends which can produce a voltage drop before the power gets to the battery, or maybe a slight short which is consuming more power than should be lost form the alternator, then you slowly run down your batter. Check all the cables to and from the alternator and battery.

As the others have said, the cables related to technical bulletins and known issues should be checked first.

McCulla

If I interpreted all of the posts I have read about these wiring problems correctly (again, you might have to do a search unless someone pipes in to give more detail...) the alternator cable is the large cable. I believe it goes all the way to the front of the car to connect to the battery and is not a simple job to replace (?). I read a description of the procedure somewhere in the last year, but I'm sorry that I can't be more specific than that. Regarding the starter wiring harness, I don't think it is actually a "melting" per se, but a conduction issue related to some problem with the harness itself and this fix requires replacement of the harness. You would need more specific information than I am able to provide personally. I know there are some WAAAY more educated sources on the board than myself, but I'm pretty sure my basics are right on this.

997at

As others have stated your issue is related to the cables that run from the alternator to the battery. Dealers should know this issue well, and there is a TSB about it. I had exactly the same symptoms, and after the cable was replaced, voila, problem solved. You'll also find your cranking is faster and more powerful. If the job is done right, I believe there are a few segments of cable that should be replaced and it is not an easy job. For peace of mind, I would have a dealer do it, or a reputable indy who has done one before.

McCulla

....what 997at said. Be sure that if you go to a shop and bring up the alternator cable that you also mention the starter wiring harness as these both seem to cause similar problems with slow crank/non starting. I seem to remember some posters telling stories about having only one of the two things fixed only to have the same problem until the other was completed. FWIW.

Lugs H

The potential problems with the battery/alternator cables & starter wiring harness was mentioned in an article in the Oct. issue of Excellence magazine.

Ciamaichelo

Thank you for all the replies... I ordered the issue of Excellence Magazine recommended above and I spoke with dealer. He states that they have changed a lot of the alternator cables and suspects a recal in the future. My connections appear clean w/o corrosion and the car is only 5 years old and garaged. I have arranged for a local Porsche mechanic to inspect the alternator cable and wiring harness. I checked the fuses and cigaret lighters as well. Now that I think about it, I have had some slow struggling starts for the past year and the symptoms have just worsenned. I left a message with Porsche NA as well to push for a recall. -Chris

boolala

Can't help you with the question of which cable is which but I don't believe that this a DIY job. The dealer quoted me about 6 hours of labor to access the cable. There should be a recall on this matter. Let us know what the dealer and PCNA tells you.

fastsvo

Hey Guys,

Any update on this potential recall? Will PCA pay for this repair on a car that just came out of warranty?

Thanks!

gota911

I don't remember hearing of an actual recall. I doubt that there was/is/will be one. If you have a good relationship with your dealer, see if they will cover it under the recent warranty.

Ciamaichelo

After much trial and error, i.e.. replacing the battery and alternator, and reading through Rennlist, I confirmed the issues with the dead batteries to be low voltage making it to the battery. The problem is heat corrosion or damage to the Alternator Cable from excessive heat in the engine compartment. In order to have this issue resolved under my Fidelity aftermarket extended warranty, I paid an extra 2 hours of labor to have the tech dissect the Alternator cable. The "heat corrosion", as the tech referred to it, was definitely not related to salt or chemical causes. It was not the white corrosion on metal that one typically imagines. The alternator cable is a 3ft long cable that connects between the rear of your alternator and the starter, each with one bolt. After dissecting the heavy rubber from the cable we found healthy copper wire with a healthy shine at one end that faded into a 1.25ft section of blackened and brittle cable at the other end. It is not from arching or a sharp bend in the cable at the starter junction as previously suggested. The problem is directly related to excessive heat that essentially burns the cable black and decreases its ability to carry the proper voltage along the way. I was averaging about 11.5 volts at my battery, which is why my battery never charged while driving. I was forced to manually charge my battery every 4 days for months,until it was all figured out. I wasted a lot of time and money on the new Bosch alternator and battery. The warranty company initially denied the claim because the tech referred to the problem as corrosion, but after explaining that it was related to heat and not the typical oxidation effects of the natural environment, they covered the claim. The dealer wanted about $1500 parts and labor for the repair and charged me a separate (min) 2 hours labor for the cable dissection. It was a gamble that worked. I was tempted to tackle it my self. I imaged I could fish the short wire through. The tech removed the top of the engine to fish it through, but never "dropped" the engine for the job.

The Porsche replacement cable is thicker with more insulation, but the new car cables are still the original thinner cables... from what I read. They have not initiated a recall or changed the new car cables to the better insulated cable, I guess that would suggest fault. I intent to call PCA again to explain my side, even though the warranty company picked up most of the tab. I hope this saves you some time.

-Chris
2005 911 Carrera S

McCulla

Interestingly, what we all said was right.....