Hello. :welcome: I'm assuming that you replaced the alternator because, for some reason, it wasn't charging. If this is a car that you just recently got and it was doing that when you got it, it could be a lot of things. If, on the other hand, this is a car that you've had for a little while and it just started doing that, this would be something else. If that's the case, I would first check and see if the alternator is actually charging. The light might be telling you the truth.:gringreen With the motor running at about 1000 rpms and with one of the doors open so that the courtesy lights are on, those courtesy lights should be slowly flickering. As you increase the rpms, the lights should flicker faster, until at 2000 rpms they quit flickering. If this is not happening, then the alternator isn't charging. To confirm this, take a volt meter and check the output at the positive battery post with the motor at about 2000 rpms. The out put should be nearly fifteen volts. If it shows 12 or less, the alternator is definitely not charging. This does not mean that you must have a bad alternator. The first thing that I would check would be the alternator ground. It runs from the back of the alternator to the lower part of the block, on the passenger side up near the front and is held on with the same bolt that holds the negative battery cable to the block. If that seems ok, it might be the voltage regulator. You can have those checked at any major auto parts chain store. It could also be a problem with the wiring that runs between the alternator and the regulator.
If the alternator and regulator are working like they're supposed to, then the problem is with the wiring of the light. Here's the wiring diagram for the 65s. I'll be making a drawing for just the charging system in the next day or so if you can wait. If not, everything is contained in this drawing. Hope that helps.
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