2000 GMC SAFARI VAN 130,000KM, 4.3 L. THE BLOWER IN MY VAN SEEMS TO ENGAGE AND KICK OFF AT IT'S OWN DISCRETION. GENERALLY IF I CROSS SOME RAILWAY TRACKS IT WILL ENGAGE. SOMETIMES IT WON'T. SOMETIMES IT RUNS GREAT FOR NO REASON. I ONCE SMASHED THE DASH NEAR THE SWITCH AND THE BLOWER STARTED OPERATING. MY GUESS IS LOOSE WIRING OF SOME KIND RELATED TO THE SWITCH RATHER THAN THE BLOWER ITSELF. WHAT DO YOU THINK?