The two fastest ways to narrow down your trouble are:

1. check that you have 12v going to the rheostat, and a varying voltage coming out of it as you turn it. This will verify you are getting power there.

2. Make sure all the screws connecting the 3 metal backing plates are tight & that they are free of corrosion between the plates where they overlap, then connect a wire from one of the screws back to a good source of ground. This will establish if you have a faulty ground.

Being that you already replaced the bulbs and the rheostat, I'm betting you are going to find it's a bad ground issue. Check all of the solder joints at the round connector for fractures.

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Chris
64 190D R.I.P.
80 240D W/617 engine -for sale
82 240D -for sale