OBC MK1 is connected to the Unit in the A pillor of the left footwell. Remove the speaker and you find one of two multiconnectors. Pull off & check if cleaning is required. Somehow I have the feeling this won't help you since you have '85 and OBC MK2. Don't know much about this one, but you might want to check on the cable to the control switch at the steering column. Best Regards Ralf