Did they work before the turn signal witch was changed out? The dimmer switch hooked up electrically. Usually the switch itself (mounted on the column) doesn't have to be messed with during a turn signal switch change out since the turn signal switch is at the top of the column, but the actuator part is in there and it can be tricky to get back into place. That's the problem child area I'd look to.
Looks something like this below. Has a weird shaped plug that goes into it, and an actuator that operates it from the pivot on the wiper stalk. Listing covers pretty much a wide range of cars, but definitely fits your 85 as it fits all G-body columns if you need to get a new switch. I still think it's the actuator in the pivot.
If your actuator up in the column needs replacing, it's GM p/n 7827028:
Sometimes when reassembling crap on the top end, the actuator rod and actuator above don't meet up properly or things slip out of place and that's not good. Not saying that's the case, but if you're not paying attention, things could get hosed up.
Check to see if the switch operates, you should be able to see if the actuator rod is actually operating the switch. Reference pic below.