hi go down the cheap route first by replacing the relay if that fails look at replacing the motors.
but if you say the both stop working at the same time then look at the relay first also check for any damaged wiring that may have got hot its unlikely but worth a look.
the other thing to do is unplug one the the motors put in a new fuse and see which one might be blowing the fuse a case of narrowing it down unfortunately its unlikely both motors have failed
hope this helps
simonvann@hotmail.co.uk
simon
February 2009