Electrical problems maybe
 

I just purchased a 2005 S40i and it was fine for the first week or so and then weird things started happening. The horn would randomly blow while driving and not stop until the car was turned off. The second time that happened, it wouldn’t stop until I removed the fuse from the engine compartment. The high beams would go on by themselves and not go off until the car was turned off. There was a similar problem with the emergency flashers. The last time it drove, the flashers and high beams went on for a few minutes before the entire display went dead. It hasn’t started since. Any ideas? I tried a new battery but that didn’t do anything.

Water intrusion into the CEM can cause a list of weird problems. xemodex.com and others can solve/repair yours if needed.