My 535is is draining its battery from full charge to dead in a matter of days. Symptoms / changes over the past 2 weeks include 1) I'm hearing a whirring sound from the radio, which fluctuates with the RPMs; 2) a cassette stuck halfway in the player; 3) I may have knicked the insulation on a small ECU (?) wire that passes just in front of the heater control valve on the firewall. Any idea what might be causing me to lose a charge so fast? The last time I heard this type noise from the radio it was due to a loose negative battery connection. I've checked that by hand, and it felt fine, but I'll check it with a wrench tomorrow. Any other ideas?