The problem is the battery drain everyday and the brakes make a annoying noise when applied, the brakes are good, so is the brake pads, less then six months repaired, but the dash lights are flashing and the brakes are making weird noise when applied.
As for the battery there's plenty of youtube vids on parasitic current drain.
or call in an auto spark.
As to the brakes they need looked at by a tech.
I know you state the pads are relatively new but I've seen some eaten in less than 6 months.
Merc pads are fitted with "screamers",
little metal tabs that run against the disk when the brakes are applied.
General idea is for a warning of impending brake failure.
" Merc pads are fitted with "screamers"," not the genuine parts I've used .Sure you are not getting mixed up with the anti rattle pad clips ? Mercs have other more sophisticated brake wear indicator methods .I doubt a 1989 would have genuine pads fitted , but possible . I had a fleet contract with a major American company and one of their engineers wore out a set of pads within 6 weeks . It was found out it was his driving and he was at it to get a new car .He had to get a new job instead !