How long should it stay on and running after ignition has been off? I noticed today that after I came back from a half-hour ride and parked the car, it was running good 10-15 minutes after the car has been shut off. It's nearly freezing temps out, so there shouldn't be any excessive heat from outside, and engine isn't running hotter than usual with no issues with cooling system that I'm aware of. I know on 540s blower motor resistor would sometimes refuse to go to sleep and cause the battery drain, but I haven't seen this particular issue before. Is this a common failure part?