How The Weekend Finished Up

[jakeru]

The following is general, non-boxster specific knowledge, but maybe helpful for you:
When automotive alternator brushes wear down so far that they stop making contact with the commutator, this will cause charging failure and voltage drop, potentially leaving you unable to start the car, or stranded on the side of the road, and various other accompanying symptoms. In this scenario, I've experienced the alternator charging "come back to life" (measured by > 14v) after letting the motor cool down completely, but it won't be a stable fix - as the brushes are just barely making contact and will continue to arc & wear, the alternator will have another charging failure soon and it will get progressively more common.

To avoid this sort of failure, when the alternator has very high miles e.g. around 200k or so, just preventively replacing the brushes is not a bad idea. If you are experiencing a charging issue and miles are > 100k, consider at least pulling the brushes and inspecting for adequate length (if not a hassle), or if it is a hassle to get to the brushes, just replace them with new (and if the problem end up being something else in the process, this will at least you ahead on preventive maintenance in the process.). I believe in the 986 alternator design, the brushes are part of the voltage regulator assembly.

You can also replace the alternator with a "rebuilt" one, or have yours rebuilt, which will include getting new sealed bearings, and lathed down commutator segments, in addition to new brushes.

[Dave S.]

I had my '03 (33k miles) up in Rocky Mountain National Park earlier this summer. As traffic was moving slowly or stopping to see wildlife, I noticed a fuel smell, like it was running very rich, a raw fuel smell. I stopped at an overlook and when I went to restart the car, the battery was dead. No check engine lights or indication of what the problem was.

Luckily I was on a hill and was able to roll start the car. I was able to drive it the 100 miles home without shutting it off or using any extra electrical accessories and when I got home, the voltage at the battery read 10 volts with the car running - so no or very little charge coming from the alternator. When I put the top up, it ran very slowly, but made it closed before I shut the car off.

I put it on a battery charger and the battery came right back to 12.5 volts and seemed to hold a good charge. The next day drove it to my mechanic. He checked out the electrical system with his Porsche diagnostic system and everything came back ok at that time. I had him replace the alternator and put in a new battery (the old one was about 10 years old anyway) even though they both checked out ok. He told me that the fuel smell was probably from the fuel injection system, which doesn't like low voltage situations and was surprised that it even ran good enough for me to make it home. I'm shocked it made it, as I was just trying to get closer so the tow would be less. It's back to being completely reliable now, and I have no idea what really happened to it. I never got a check engine light or any lights to indicate it had a problem. First issue this car has ever had.

[rexcramer]

Thank-you again for your suggestions. I have taken it out 3 times for +/-100 miles and no problems/CEL's. I hooked a multi-meter up to the battery and ran a wire into the cab so I can watch the voltage. Normal so far.

Autozone did use a load test on the battery and their alternator test machine is very cool. Both are within spec.

The cables and connections are pristine. There are zero signs of corrosion anywhere I can see. I haven't checked every ground strap yet.

I have used the battery donuts for years. They are cheap insurance.

The firewall positive cable connection has a stud and bolt with a plastic cover on it. (97 Tip) It is tight and clean. I haven't pulled the high amp fuse cover off yet.

I did pull the voltage reg off and inspected it while I had the Alt out. It looks to be in good shape. No discoloration and the length appears to be okay.

The car has 24K on it. 8K are mine in the last 13 months. Needless to say, I am reluctant ($$$) to just X/O the alternator on a maybe. I am going to start driving it to work (50 Rnd Trip) and see how it goes. I am getting close to an oil change and will probably let my indy do it and give it a complete physical while it's in the shop.

Safe travels, rx