djlod

Do I need to replace my alternator?
I have a walmart Maxx 49 battery that is 1 month old (I'm not noticing any problems).
I went to the Interstate battery store (I have a friend that works there) today to check on my battery.
The voltmeter read 12.8 volts (idling).
When I gave it some gas or turned on my headlights the volts went down to about 12.6 volts.
I was told that the battery should read at least 13 or 14 volts, if not I could have a problem with the alternator.

History...
Aug 16, 2010 - My OEM Moll battery finally died (starting the car was becoming increasingly difficult), so I replaced it with a Walmart Maxx 49 battery (my 2006 997 was initially purchased Oct 2005).

Oct 18, 2010 - My walmart battery was initially strong. My 997 is a daily driver. The first two weeks of October I did not drive my 997 daily. I let it sit for 3-4 days, and then would only drive it a few miles. I began to drive it everyday again. After a few days, I noticed that I was having a hard time starting the car. The battery died and I exchanged my walmart battery for a new Maxx 49 battery (hoping it was a defective battery).

I called my friend who is a service tech at a porsche dealer, and he said I should be ok. I plan on having him check out the car in a week.
What do you guys think?
Thank you in advance.

gota911

Just trust your tech (friend) at the Porsche dealership. It very well could be the alternator, but the wiring harness from the starter is a known problem in early 997 cars and can cause weak starts and increased battery drain. Have your friend check the TSB for that.

Good luck. Let us know what the outcome is after the visit to the dealer.

djlod

Thanks for the info Tim.
I will definitely post what the outcome is.
David

jhbrennan

I do know that the correct size (dimensions, not necessarily specs) is the 94R not the 49. The 49 is longer and maybe is putting greater demands on the alternator if it's spec'ed differently than the OEM or the 94R. Let us know what you find out.

acadian_dad

Just one quick thought ... I had suspected an alternator problem on my car - was seeing ~12V running like you ... or at least I thought I was ... then I borrowed a properly calibrated DMM from work and low and behold ... it was my cheapo home DMM that was messed up. The battery and alternator were fine. After a long debug at the dealer, turned out my alarm control module was faulty - because the car was not properly locking, the power draws were not all being turned off and I basically had a power draw while the car was idle. New alarm control module solved the issue. (2005 997 C2S Cab)

So just suggesting you double check your DMM ...

djlod

Thanks for the replies guys.
I will ask my service tech to check the DMM.

djlod

I just got back from the dealer and had my car checked out.
It's the cable from the alternator that is causing weak starts and increased battery drain.
There's a TSB (bulletin) for this issue, but since my car is 5 years old, the dealer will not cover it.
I'm getting charged $700 for parts and labor.
Thanks Tim, you were correct.

boolala

I have the same problem. It's cheaper to replace the battery every 3 years. I have never been stranded.

Should have been a recall by Porsche.

djlod

I was hoping that Porsche would cover it, but the dealer said they would not cover it because I was out of warranty.
I was told that the cable was crimped which didn't allow the alternator to fully charge the battery.
I took a look at the old cable, the plastic covering had melted onto the cable.
The cable was $200, and $500 for labor.
This morning the voltmeter read 12.7 (idling).
After the new cable, the voltmeter read 14.0 (idling).