Jump to content

Server Lease Renewal/Software Licenses

Our yearly server lease, software licenses, as well as hardware operating costs, ARE due Dec 6th, 2021. Our current donations have fallen far short of the funds we need to renew. Please remember the RennTech.org community is Member supported so please consider a donation to help...  THANK YOU!

Welcome to RennTech.org Community, Guest

There are many great features available to you once you register at RennTech.org
You are free to view posts here, but you must log in to reply to existing posts, or to start your own new topic. Like most online communities, there are costs involved to maintain a site like this - so we encourage our members to donate. All donations go to the costs operating and maintaining this site. We prefer that guests take part in our community and we offer a lot in return to those willing to join our corner of the Porsche world. This site is 99 percent member supported (less than 1 percent comes from advertising) - so please consider an annual donation to keep this site running.

Here are some of the features available - once you register at RennTech.org

  • View Classified Ads
  • DIY Tutorials
  • Porsche TSB Listings (limited)
  • VIN Decoder
  • Special Offers
  • OBD II P-Codes
  • Paint Codes
  • Registry
  • Videos System
  • View Reviews
  • and get rid of this welcome message

It takes just a few minutes to register, and it's FREE

Contributing Members also get these additional benefits:
(you become a Contributing Member by donating money to the operation of this site)

  • No ads - advertisements are removed
  • Access the Contributors Only Forum
  • Contributing Members Only Downloads
  • Send attachments with PMs
  • All image/file storage limits are substantially increased for all Contributing Members
  • Option Codes Lookup
  • VIN Option Lookups (limited)

Voltage drop between alternator and battery

Recommended Posts

In my 2005 997 manual Carrera S with Chrono pack, I have had an intermittant problem of the car

failing to start due to a battery with too low a charge. I drive this car daily. No dash battery discharge

warning indication has ever shown.

Recently I changed the battery, and then had a regulator failure requiring a new one. 4 weeks,

later, after a few starts during the day, the car failed to start due to low battery.

To shorten the story, I discovered there is a 1 volt voltage drop in the thick positive wire that

travels the length of the car from the alternator to the battery. Trouble shooting indicates the

problem is between the alternator, and the connector next to the gearbox. The generator/regulator

puts out 13.8V, but at the battery the voltage varies between 12.5 and 13 V.

I suspect it is where 2 wires are pre joined at the starter motor solonoid, since there are

no other connectors, and the wire is unlikely to have been damaged.

Before I go removing the air filter and fuel injection plenium chamber to get behind the starter

motor, I have a couple of questions.

Is this an uncommon problem, or is it a known design fault?

If anyone has had this before, what was the cause?

Why doesn't the battery discharge warning on the dash come on to warn me?

Link to comment
Share on other sites

I think your analysis is correct. The alternator voltage is correct, and the battery voltage is too low to charge the battery. The drop you measure is the problem, and is most likely occurring at the connection at the starter motor. Unless there has been a crimp or cut in the wire between the alternator and the starter, the connectors on the wire or, most likely, the tightness of the connection at the starter are the culprit. Good analysis, and good luck.

Link to comment
Share on other sites

The 997-2 cars have a bigger wire. I had this installed when

they replaced the motor. If you have a tip car, then it is almost impossible

to replace. A manual is easier because there is no huge transmission

cooler sitting on top of the transmission.

One thing I did that helped a little was remove the connection under the car

on the passenger side and sand paper the connection. The connection is behind

a plastic door that picks up alot of road dirt.

This is a common problem with the 997-1 cars.


Link to comment
Share on other sites

  • 2 months later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.