[JSeery]

What type of wiring harness was used, is it one of the original cloth covered types, or one made up wire by wire? There are several connections on the light control switch, seems like either the connections are wrong or the switch is bad (just a guess here based on your post). Do you have the wiring diagram?

Per the wiring diagrams the lighting control switch is different between the cars and the commercial, that might be able to lead to an issue.