Volvo Repair: 1988 240 battery issues, car check, charging system

Question
My son married into a 1988 240 Sedan. The battery had died and replaced it to spec. Two weeks pass and now it won't start. I'll have to have the battery checked tomorrow. But. There is a black and a red wire connected the the Positive lead. They all just clamp together on the the battery positive. The black one came loose. I have no idea what this is. Do you?  

Answer
Ellis, it should be red but on the driver firewall there is a black junction block that feeds the inside of the car and that wire is usually connected to the positive terminal with the cable.  There also could be a draw on the charging system causing the battery to drain.  Have the battery checked.  I would have the car check by a volvo shop. Roger