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

 

I just had my alternator cable / harness replaced.
PM me if you have any questions.
If you can't PM me, leave me your email address and I'll email you.
Here's my thread about my alternator to battery cable problem.
https://www.6speedonline.com/forums/...lternator.html
Good luck.

 

my 06 c2s had a slow crank issue.
they replaced the battery/starter cable
hope this helps

 

Thank you for your 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

 

1234

 

1234

 

putput6- it was done under warranty. they also removed the engine a second time to replace the rear main seal, also under warranty three months later. you think the dealer would do the rms while the engine was out the first time. it was not until i told them there was oil leaking that they did something. i guess its just more money to charge porsche.

 

the fat stiff cable that bolts to the back of the alternator.
I'm not sure if this job is a DIY.
Email me or leave me your number and I'll call you.
Good luck.

 

thank you all... I think I have my answer. I will post the results. Djlod analrapist, the system does not allow me to PM. My email is ciamaichelo@mac.com.

-Chris

 

LOL.
Perhaps I should change my avatar.
I will email you.

 

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

 

Glad to hear you finally got it resolved after much troubleshooting. You've got to love how warranty companies try to wiggle out of covering repairs. I am glad you had a good result. Back to enjoying driving

 

Great info!

 

My 07 C2S is in the shop right now having the alternator wiring loom replaced. I believe that's a $1200 job if not under warrenty. They also found my alt. wasn't outputting to spec so that's being replaced as well. My CPO just paid for itself.

 

Glad to hear CPO covers this. My indy shop told me that my 06 C2S cab may need this cable replaced, as apparently it was a known problem on the 06 models (possibly others according to this thread). The only times I have a cranking problem is when the car is at operating temp and I accidentally stall it (doesn't happen often). At those times, when I try to immediately re-start the motor it barely cranks, almost like a nearly dead battery. Any other time it cranks fine. I'm going to take it to dealer this month to have it checked to see if that cable needs replacing under my CPO warranty before it expires next March.