I have a 1996 Windstar with 3.8L engine. When the car idles, ther is noticeable flicker of the head lights, dome lights, and instrument panel. They flicker at ~7x per second. I replaced the alternator (despite testing OK), but there was no improvement. The battery is new (replacement was a little while before noticing the flicker). The flicker goes away when the rpm is increases. An oscilloscope shows that there is a voltage ripple, but it looks like about 0.5 volts p-p. The ripple frequency seems to match the flicker rate. I have cleaned the battery terminals and checked the ground between the battery and the engine block.
The alternator puts out 35 v when the B+ wire is not connected, as if the regulator is not working correctly.
I think that it is either (1) bad battery (2) bad alternator (3) broken or shorted wire.
Any ideas?
Tom