My son's used Volvo S40 (2005) has a problem...the windshield wipers will sponateously come on while driving (and it's NOT raining), and then they won't come on when you need them...and they'll come on when you open and use the passenger side vanity mirror. It was suggested we replace the motor, which we did, but that didn't fix it. Help! Tell me it is not a computer issue, which I was told might cost 2000.00 to fix.