The dimmer? It's by the foglight and defroster switch on 89+. If that's not doing the trick it may need replacing. You can bypass it by jumping the white wire with the green stripe to the white wire with the black stripe where the harness plugs into the dimmer.
Nah, it gets confusing trying to go by years for stuff like that, because the change was made with airbags, which happened for 1990 in the USA, 1992 for Canada, and the rest of the world never really got them.
Heh, I knew airbags were '90 here in the states, didn't realize they didn't make it to Canada until '92. So many little changes, at so many different times... ugh. I don't know how you keep it all in your head, but I'm glad you do.