I have a problem with my sons 1991 240. A week ago, it would not start but could be jump started with no problem. I replaced the battery,which was very oldand the car started right up. Problem solved right? Nope. 5 days after replacing the battery, and the car starting with no problem, it sat for 3 days and when I tried to start it, nothing. No clicks, no chime, no lights...nothing. Jump started it first try, let it run for about 15 min turned it off and it started right up again. No starting problems for several days then once again, in the morning, totally dead. No lights, chimes, clicks or anything. Jump started easily and ran several more days before the cycle repeated. I have had the charging system checked and it is working fine. Other than it letting the new battery die every 3 or 4 days. This always happens overnight.

The alternator belt seems tight but I have had an occasional belt squeal, comes and goes, for the past three weeks or so. I am wondering if it could be related.

Any thoughts are appreciated. I am tired of jumping the car off.