1989 Buick Park Avenue 6 cyl Front Wheel Drive Automatic 309000 miles
Ok I own an 89 buick park avenue and I recently noticed that the voltage gauge in the dash, along with the headlights, would fluctuate. I tends to do it more at idle than on the highway although it still does it a bit while driving. Also, the blinkers will cause quite a large drop of voltage. If, at Idle, I disconnect the positive terminal on the battery, the car dies. If the throttle is held down a little bit and I disconnect the battery, it will keep running.
Sounds to me like a diode is open and the alt. Is only putting out 2/3 of it's potential so I had the alternator tested at a shop and according to them, it is functioning correctly. I have also tested the battery connections.
Yes it does sound like a bad diode or possible bad votage regulator, taking off the battery cable is not a good way to check the alternator anymore you can cause more damage to the vehicle either to the alternator or to the vehicle computor. Could also be a bad battery you may want to have the battery checked if it checks out to be good then the problem is in the alternator replacing it will also replace the voltage regulator.