T660 can visor lights not working

[Moose]

Assuming the fuse is good:

If the CECU detects a fault (short to ground or excessive current) it will turn it off to protect the circuit. If by chance they are tied together with the trailer clearance lamps try unplugging your cord at the tractor and seeing if it corrects itself after a key cycle. KWs also have the extra clearance lamp switch, check that too.