Here it was again. Dreaded alternator warning light. I just drove for about 100 highway miles with my 1998 993 cab 2 (63k miles) when after refueling I noticed a faint alternator warning light come up. And I barely replaced my 3 belts and battery about 600 miles ago.

What was surprising this time, was that the light didn't just go on. It glow more right when I accelerated from standstill, to disappear again.

About 20 miles later, as my alternator light slightly came through again, my warning light, anti lock, then airbag jumped on. I was able to make it home until every possible warning light jumped on and my battery seemed drained as I couldn't even turn my litronics lights on (beyond parking) .

What is going on? Need for new alternator? Belts are still ok. Any idea on repair costs in California?

is it normal that the alternator gives up at 60k-ish miles? My 1997 BMW 328 has 210k miles and I never had any issues with my alternator.

Help!

Jf

 

One more datapoint: I was driving with the top down (got to love california in the winter), temp regulator on 24, fan on 3 or 4, and litronics on, and using the cigarette lighter to power my phone/gps for about 2 hours.

 

- check connections @ the battery, and continuity of the ground strap/cable ..... a cheap digital multimeter is invaluable! (<$20)
- place battery on charger for a few hrs: nearly new battery should come up to 12.5V+/-.2V
-start car, bring to a fast idle: measured voltage at battery terminals ( not the cables, but the lead posts of the battery!!) should be ~14.0V

If not, the regulator/brush set in the alternator is the more probable fault.

A new brush set runs ~$25 ..... an easy DIY to pull & replace in sunny CA.

 

Garth, no less than 12.65V and that open circuit voltage reading should be taken at least 4 hours after the battery charger has been disconnected.

A 12.3V battery is about half charged.

And a few hours may not be enough. It depends on the charging rate and level of discharge. When the charger has reached 14.4 volts and remains there for a few hours after the charging current tappers off to almost nothing, then the battery is fully charged.

 

All so true .... but a quick 12.3V recharge is more than adequate to allow a car to be started for a basic alternator/cable/connection check - which appeared to be the thrust of the query.

I suspect that our new colleague Mizuno would be unlikely to seek our input if he either had a DVM ( digital volt meter), or knew what basic voltage measures are required to evaluate and sort out these types of issues: the basic info provided was a gentle prod onto the road of self enlightenment ... where a $20 DVM can save $$$$$ ....

 

Garth, I picked up this DMM at Walmart in the US for $12 ($25 up here at Walmart...must be the exchange rate ). Switch action is good for a DMM at that price...and I own a Fluke 88V. At that price I can afford to have it in my "kit" in the car.

 

Thank you all. Very helpful. A DMM it will be.

Just a quick follow up question: Besides the brushes, why did you rule out the alternator working well? Is it inconsistent with any of the symptoms I listed?

Thanks!

 

Same thing happened to me, installed brush set in alternator, fixed.

 

Even more useful is an in-car mounted voltmeter which tells you how your charging system is operating at all times.




Brushes are a wear item. The possibility of the electronics in the voltage regulator or diodes in the rectifier failing are always there, but they are not really a wear item and if properly designed, rarely fail. Same for the windings in the rotor and stator.