Alternator Light Readings?

ErikT · ErikT's Garage

Hi,

1) I replaced the alternator this weekend with a rebuilt model from Alternator Express.com. It came with a new Paris Rhome regulator. I put the belt on with proper tension, drove it around for awhile during the day to recharge the battery. The car ran great.

2) This evening, when the dark came...I was driving and noticed that the Alternator Indicator Light came on and increased in brightness as the RPMs went up. The Alt Light goes out when the car is at idle.

The voltage readings appear normal, as speced in Bentley and Dempsey:

12.7 V at battery when car is off.
13.25 V at battery when car is idling at 700 RPM
13.55 V at battery when car is under load at 1500 RPM.

According to Bentley and Waynes book.... a light on at increased RPM could mean just about anything: bad alternator, bad regulator, disconnected battery-alternator connector, disconnected ground.

I know that its not a disconnected wire... so Im left with a possible bad alternator or bad regulator....

But wouldnt those things show themselves with irregular Voltage readings?

ErikT · ErikT's Garage

Bump...there isnt much in the archives regarding this particular alt light issue. Thanks.

ruf-porsche · ruf-porsche's Garage

If the battery was dead and you got a jump start to start the car, the alternator would not charge the battery fully unless you drove it the entire day. Try charging the battery with a battery charger and see if you still have the problem. Also have the battery tested, could be a dead cell.