Alt light on at idle - ok to drive?

[Christien]

My alternator will come out for a rebuild in a couple days, because the light's on at idle, and only fading to about 1/4 brightness above 2000 rpm. Am I ok to get away with some driving in the meantime? Will I be charging the battery enough when I'm above 2000 to keep it from draining when I'm idling at a red light, stop sign, etc? Obviously I'll be avoiding traffic jams, and it'll only be for a few days, but I definitely don't want to get stranded.

My experience with my 944 when my VR died was that I was able to drive for about 30-40 minutes on the highway before the car died on me. That was a fun surprise Obviously the 911's not running just on battery, but that experience tells me that the battery holds a lot of juice.

[autobonrun]

That's a tough question because it's difficult to say just how much charge "dim" represents. We know what the light off and full on means. If you don't have many days until it's being checked, I'd wait.

If I had to drive, I'd use a voltmeter to measure the battery voltage first. Drive but stay close to home. Come back and remeasure the voltage. If it stays the same or increases you should be ok. If it started to drop even a few tenths of a volt, I'd park it. Towing gets expensive.

[Christien]

When this happened, I was out of town. It was fine driving there, hopped in the car to drive home, fire it up, and 'oh, nice, the light's on'. Drove home an hour and a half (20 min. city, just over an hour highway) and measured the voltage the next morning. I got good #s: off: 12.75, idle: 12.36, load (3k rpm): 14.77.

[autobonrun]

Originally Posted by Christien

When this happened, I was out of town. It was fine driving there, hopped in the car to drive home, fire it up, and 'oh, nice, the light's on'. Drove home an hour and a half (20 min. city, just over an hour highway) and measured the voltage the next morning. I got good #s: off: 12.75, idle: 12.36, load (3k rpm): 14.77.

With those numbers, I'd feel ok driving it.

Now you have an excuse for speeding. Tell the cop you have to keep the rpm's over 3k.

[Peter Seow]

no problem at all i had to go without my alternator for an hour of driving my belt loosen and the alternator was not really charging i pulled the belt off. but had no tools to put it back.

[Christien]

That's what I thought - thanks for setting my mind at ease.

[E Sully]

With a fully charged battery you can run for a short while, but it could be a problem. Voltage at idle,12.36, shows it is not charging at all. 14.77V at 3000 is a bit high. If you get a voltage spike from a bad regulator you could burn out some electronics or damage the battery.
Pete, running without a belt could easily cause over heating in an air cooled engine. The belt also turns the fan.

[T77911S]

basically, the battery is there jsut to start the car. an alt is capable of putting out 90 amps or so, more than enough to power the car. my concern would be that the alt completely dies while driving, and yes you can drive for quite a while on just the battery, shorter if you have to use lights. lights are a big power drain, keep your foot of the brake while stopped will help if the alt dies and you have to run on battery.

[Peter Seow]

Originally Posted by E Sully

With a fully charged battery you can run for a short while, but it could be a problem. Voltage at idle,12.36, shows it is not charging at all. 14.77V at 3000 is a bit high. If you get a voltage spike from a bad regulator you could burn out some electronics or damage the battery.
Pete, running without a belt could easily cause over heating in an air cooled engine. The belt also turns the fan.

But i was heading off to a highway with only two traffic light stops on a cold engine.

No over heating occurred.

[gtc]

Originally Posted by Peter Seow

no problem at all i had to go without my alternator for an hour of driving my belt loosen and the alternator was not really charging i pulled the belt off. but had no tools to put it back.

No offense but....
This is about the worst thing you could have done.... driving the car without the fan spinning is pretty effing stupid.

[Wil Ferch]

Do a search.. I don't have all the electrical details in front of me but the car should never be run with the alternator disconnected or not functioning.